BIO 1103 GPC ATP Worksheet

MONETTE P
Glycolysis Respiration and Fermentation CHAPTER 7
Chapter 7.1
Explain how ATP is used by the cell as an energy source
•Describe glycolysis as the most basic way to get ATP from sugar
Not only does it need sugar, but it also needs ADP, and NAD+ to run.
•Describe the reactants and products of the energy investment phase
and the energy harvesting phase of glycolysis
•Relate the molecules used in glycolysis to the same molecules used in
photosynthesis
Chapter 7.2
Describe the location of the prep reaction, citric acid cycle and
oxidative phosphorylation in the cell
•Describe the reactants and products of the prep reaction, citric acid,
and oxidative phosphorylation
•Describe the relationship of glycolysis to cellular respiration in terms
of pyruvate, NAD+, and NADH
•Relate the molecules used in respiration to the same molecules used
in photosynthesis
Chapter 7.3
Explain why the ETC cannot convert NADH to NAD+ in the absence of
oxygen
•Identify fermentation as a process to return NAD+ to glycolysis
•Describe the reactants and products of both kinds of fermentation
Summary chapter 7
Glycolysis is breaks down glucose into two pyruvate molecules
and results in a net gain of two ATP molecules.
•The citric acid cycle is a series of chemical reactions that removes
high-energy electrons that will later be used during the electron
transport chain to generate ATP. One molecule of ATP (or an
equivalent) is produced per each turn of the citric acid cycle.
•The electron transport chain uses chemiosmosis to produce a lot
of ATP.
•In the absence of oxygen, fermentation is used to regenerate
NAD+, ensuring the continuation of glycolysis.
Ch 8 Cellular Reproduction
Chapter 8.1 Learning Goals
•Describe bacterial and eukaryotic genomes
•Distinguish between a whole genome, individual chromosomes, and a
plasmid
Chapter 8.2 Learning Goals
•Explain that most body cells are in G0 and are not actively growing or
dividing
•List the three stages of interphase and the key events that occur in each
stage
•List the five stages of mitosis and the key events that occur in each stage
•Discuss the behavior of chromosomes during mitosis and how the
cytoplasmic content divides during cytokinesis
•Explain when each of the three checkpoints occurs and what each is
looking for
Chapter 8.3 Learning Goals
•Explain how a tumor is caused by cells that should be in G0 moving
into G1 and beyond
•Describe cancer as a disease caused by malignant tumors
•Explain how proto-oncogenes and tumor suppressors can cause
tumors when mutated
Summary CHAP 8
•Prokaryotes have a single loop chromosome, whereas
eukaryotes have multiple, linear chromosomes
surrounded by a nuclear membrane.
•The cell cycle is a highly ordered and closely regulated
sequence of events.
•Each step of the cell cycle is monitored by internal
controls called checkpoints.
•Cancer is the result of unchecked cell division caused by
a breakdown of the mechanisms regulating the cell
cycle.
Ch 9 Reproduction and Meiosis
Explain the difference between diploid and haploid
genomes
• Describe the ways in which homologous
chromosomes are very
similar to each other while still having some
differences
• Explain the advantages of asexual and sexual
reproduction
• Describe the three different life-cycle strategies
among sexual
organisms and give example organisms for each
Chapter 9.2 learning goals
Define meiosis as a process that converts a diploid
cell into 1 or 4
haploid cells
• Explain the differences between meiosis and
mitosis
• Describe how the separation of homologous pairs
during Anaphase I
converts diploid cells into haploid cells
• Explain the mechanisms within meiosis that
generate genetic
variation among the products of meiosis
Summary
• Diploid cells contain two sets of chromosomes
whereas haploid cells contain
one set.
• Asexual reproduction allows an organism to reproduce
itself quickly without
requiring a partner. Sexual reproduction results in
genetic diversity.
• There are three main categories of life cycles in
multicellular organisms:
diploid-dominant, haploid-dominant, and alternation of
generations.
• Meiosis is the form of nuclear division that results in
haploid daughter cells
forming from diploid cells. Meiosis also results in genetic
diversity due to
crossover and independent assortment.
• Nondisjunction during meiosis can result in disorders.
Chapter 10 Patterns of Inheritance
Chapter 10.1 Learning Goals
• Explain the scientific reasons for the success of
Mendel’s experimental work
• Describe the expected outcomes of monohybrid
crosses involving
dominant and recessive alleles
Chapter 10.2 Learning Goals
• Explain the relationship between genotypes and
phenotypes in
dominant and recessive gene systems
• Use a Punnett square to calculate the expected
proportions of
genotypes and phenotypes in a monohybrid cross
• Explain Mendel’s law of segregation and
independent assortment in
terms of genetics and the events of meiosis
• Explain the purpose and methods of a test cross
Chapter 10.3 Learning Goals
• Explain how heterozygous phenotypes differ in
codominance,
incomplete dominance, and multiple alleles.
• Explain how polygenic phenotypes result in
continuous traits.
• Explain why recessive, sex-linked phenotypes show
up more often in
males than females.
Summary
• Mendel postulated that genes (characteristics) are
inherited as pairs of alleles
(traits) that behave in a dominant and recessive pattern.
• Alleles segregate into gametes such that each gamete is
equally likely to receive
either one of the two alleles present in a diploid individual.
In addition, genes
are assorted into gametes independently of one another.
• Alleles do not always behave in dominant and recessive
patterns.
• Incomplete dominance describes situations in which the
heterozygote exhibits a
phenotype that is intermediate between the homozygous
phenotypes.
• Codominance describes the simultaneous expression of both of
the alleles in the
heterozygote.
• Genes that are present on the X but not the Y chromosome are
said to be X-linked,
such that males only inherit one allele for the gene, and females
inherit two.
Chapter 11 Molecular Biology
Chapter 11.1 Learning Goals
• Explain the contributions of Franklin/Wilkins and
Watson/Crick to the
discovery of the structure of DNA
• Describe the structure of a DNA monomer, a DNA
polymer, and a DNA
double helix
• Explain how hydrogen bonding determines which
bases pair up across
the double helix
• Describe how eukaryotic and prokaryotic DNA is
arranged in the cell
Chapter 11.2 Learning Goals
• Describe DNA replication as a semiconservative
process where one
old strand is matched with one new strand in each
double helix
• List the four basic steps of DNA replication
• Explain how hydrogen bonding between
complementary base pairs
determines which base is added to a new DNA strand
• Describe the three main mechanisms of DNA repair
and how they
lower the mutation rate to less than 1 in a billion
Chapter 11.3 Learning Goals
• Explain the central dogma
• Explain the main steps of initiation, elongation, and
termination
• Identify three key differences between DNA
replication and RNA
transcription
• Describe the steps of eukaryotic mRNA is
processing and the purpose
behind each step
• Avoid key errors related to the central dogma
Chapter 11.4 Learning Goals
• Describe the Genetic Code as a match between
each mRNA codon
and a specific amino acid
• Explain how tRNA complements mRNA to match
codons with specific
amino acids
• Describe a ribosome as an enzyme that links amino
acids together
after tRNA complements mRNA
Summary
•A DNA molecule is double-helix. Each strand is composed of
a sugar phosphate
backbone with nitrogenous bases extending from it. The
bases of one strand bond
to the bases of the second strand with hydrogen bonds.
•DNA replicates by a semi-conservative method in which each
of the two parental
DNA strands act as a template for new DNA to be synthesized.
•Transcription creates RNA from a DNA template. Newly
transcribed eukaryotic
mRNA are modified and exported from the nucleus for
translation.
•The central dogma describes the flow of genetic information
in the cell from genes
to mRNA to proteins.
•Translation is the process of using mRNA to synthesis
proteins. The genetic code is
“translated” by the tRNA molecules, which associate a specific
codon with a
specific amino acid.
Chapter 12 Biotechnology
Learning Objectives
• By the end of this section, you will be able
to:
• Explain the basic techniques used to
manipulate genetic
material
• Explain molecular and reproductive cloning
Learning Objectives
• By the end of this section, you will be able
to:
• Describe uses of biotechnology in medicine
• Describe uses of biotechnology in
agriculture
Summary
•Nucleic acids can be isolated from cells and then
amplified and
separated to perform analysis, such as DNA profiling.
•Cloning may involve cloning small DNA fragments
(molecular cloning) or cloning entire organisms
(reproductive cloning).
•Genetic testing can be performed to identify
diseasecausing genes in individuals.
•Vaccines, antibiotics, and hormones are examples
of
products obtained by recombinant DNA technology.
•Transgenic organisms possess DNA from different
species.
Glycolysis, Respiration, and
Fermentation
The Glucose Catabolism: A Preview
• Harvesting of energy from glucose has three stages
• Glycolysis (captures energy as ATP and NADH)
• The citric acid cycle (captures energy as ATP and NADH)
• Oxidative phosphorylation (uses NADH to make a LOT of
ATP!!!)
Cytoplasm
Matrix
Cristae
GLYCOLYSIS
Chapter 7.1 Learning Goals
• Explain how ATP is used by the cell as an energy source
• Describe glycolysis as the most basic way to get ATP from sugar
• Describe the reactants and products of the energy investment phase
and the energy harvesting phase of glycolysis
• Relate the molecules used in glycolysis to the same molecules used in
photosynthesis
Stage 1: Glycolysis
Glycolysis (“sugar splitting”):
• First step in breaking down glucose for extraction of
energy
• Takes place in the cytoplasm of all cells
• Needs no oxygen
• Breaks down one molecule of glucose into two molecules
of pyruvate
There are two phases in the glycolysis
pathway:
Energy investment phase:
• Uses two ATP to split glucose
into two small sugars
Energy harvesting phase:
• Two molecules of NAD+ reduced
to two molecules of NADH
• Four ATP formed
• Net gain of two ATP molecules
• Two pyruvate molecules are left
over
Glycolysis Requires NAD+!!!
Glycolysis requires sugar, ADP, and NAD+ to run
• If you run out of ADP, it means you turned it all into ATP
(this is not a problem)
• If you run out of sugar, your body can break down fat and
muscle to create sugar
• You have far less NAD+ in your body. If you convert it all to
NADH, glycolysis shuts down
Keep this in mind . . .
Glycolysis and Photosynthesis
Glycolysis and Photosynthesis share some common players
• G3P (intermediate of glycolysis, product of calvin cycle)
• NADH/NADPH (product of glycolysis, product of PSI)
• ATP (product of glycolysis, product of PSII)

CELLULAR RESPIRATION
Chapter 7.2 Learning Goals
• Describe the location of the prep reaction, citric acid cycle and
oxidative phosphorylation in the cell
• Describe the reactants and products of the prep reaction, citric acid,
and oxidative phosphorylation
• Describe the relationship of glycolysis to cellular respiration in terms
of pyruvate, NAD+, and NADH
• Relate the molecules used in respiration to the same molecules used
in photosynthesis
Stage 2: Prep Reaction
• In the presence of oxygen, the pyruvate formed in glycolysis is
transported from the cytoplasm into the matrix of the
mitochondrion.
Stage 2: Prep Reaction
In the prep reaction, pyruvate (3 carbons) is converted to acetyl (2 carbons)
1. a carboxyl (-COO) group is removed and given off as CO2,
2. NAD+ is converted to NADH, and
3. coenzyme A joins with the leftover two-carbon sugar to form acetyl coenzyme A,
abbreviated as acetyl CoA
Stage 3: Citric Acid Cycle
Two molecules of acetyl CoA enter the citric acid cycle because we had
two pyruvates from glycolysis.
During the eight steps of the cycle:
• the two-carbon acetyl sugar combines with a four-carbon sugar,
forming citrate (citric acid)
• citrate is degraded back to the oxaloacetate,
• 2 CO2 are released, and
• 1 ATP, 3 NADH, and 1 FADH2 per turn.
Stage 3: Citric Acid Cycle
Totals
The citric acid cycle processes two molecules of acetyl CoA for
each initial glucose.
After glycolysis, prep reaction, and citric acid cycle, the cell has
produced
• 4 ATP
• 10 NADH
• 2 FADH2
• 6 CO2 (waste)

Citric Acid Cycle and Photosynthesis
Glycolysis and Photosynthesis share some common players
• NADH/NADPH (product of citric acid cycle, product of PSI)
• ATP (product of citric acid cycle, product of PSII)
• CO2 (product of citric acid cycle, reactant of calvin cycle)
• Reusable 4-carbon (citric acid cycle) or 5-carbon (calvin
cycle) sugar
Stage 4: Most ATP production occurs by
oxidative phosphorylation
• Following glycolysis and the citric acid cycle, NADH and
FADH2 account for most of the energy extracted from food
• These two electron carriers donate electrons to the electron
transport chain, which powers ATP synthesis via oxidative
phosphorylation
© 2018 Pearson Education, Inc.
Electrons are passed through a number of proteins to O2
• Oxygen draws electrons towards it as it is highly electronegative
• Acts at the final (low-energy) electron acceptor, forming water
Electron transport pumps H+ into the cristae folds of mitochondria
Cristae
O2
Matrix
INTERMEMBRANE SPACE
• ETC proteins pump H+ from the
mitochondrial matrix into the cristae
• H+ then moves back across the
membrane, passing through a
combination channel/enzyme, ATP
synthase
• ATP synthase uses the push from the H+
flow to cram a phosphate onto ADP,
making ATP
H+
Rotor
Internal
rod
Catalytic
knob
ADP
+
P
MITOCHONDRIAL MATRIX
ATP
Review: Each molecule of glucose yields many
molecules of ATP
Glycolysis, citric acid cycle, and oxidative phosphorylation produce up
to 36 ATP molecules for every glucose molecule oxidized in cellular
respiration.
• 2 from Glycolysis
• 2 from Citric Acid Cycle
• 32 from oxidative phosphorylation
KEY POINT – All NADH is now back to NAD+, meaning glycolysis can
continue. But what if you had no oxygen to run the ETC . . . ?

Oxidative Phosphorylation and Photosynthesis
Oxidative Phosphorylation and Photosynthesis share some
common players
• NADH/NADPH (reactant for ETC, product of PSI)
• ATP (final product of respiration, intermediate of
photosynthesis used by calvin cycle)
• H+ (pumped and used to make ATP in both respiration
and PSII)
• O2 (final reactant of ETC, waste product of PSII)
Breathing supplies O2 for use in cellular
respiration and removes CO2
• Respiration, as it relates to breathing, and cellular respiration
are not the same.
• Respiration, in the breathing sense, refers to an exchange
of gases. Usually an organism brings in oxygen from the
environment and releases waste CO2.
• Cellular respiration is the aerobic (oxygen-requiring)
harvesting of energy from food molecules by cells.
O2
Breathing
CO2
Lungs
O2
Transported in
bloodstream
CO2
Muscle cells carrying out
Cellular Respiration
Glucose + O2
CO2 + H2O + ATP
FERMENTATION TO REGENERATE NAD+
Chapter 7.3 Learning Goals
• Explain why the ETC cannot convert NADH to NAD+ in the absence of
oxygen
• Identify fermentation as a process to return NAD+ to glycolysis
• Describe the reactants and products of both kinds of fermentation
Without Oxygen the ETC Cannot Run
• In the absence of oxygen, the ETC cannot get rid of lowenergy electrons at the end.
• Electrons are stuck in
place at every pump, so
the pumps cannot gain
new energy.
• This means NADH
cannot be turned into
NAD+ at the first step.
ee-
ee-
Without NAD+ Glycolysis FAILS!!!
• NAD+ is a required reactant for the
energy harvesting phase of
glycolysis
• Without NAD+ glycolysis shuts
down
• No glycolysis = no ATP = cell death
Fermentation Turns NADH
Back to NAD+
• Pyruvate and NADH from
glycolysis become reactants for
fermentation.
• The NAD becomes NAD+ and the
pyruvate becomes either
Lactic acid (bacteria, you)
Ethanol + CO2 (fungi)
• Glycolysis continues, the cell lives
The baking and winemaking industries have
used alcohol fermentation for thousands of
years.
In this process, yeast (fungi)
• convert NADH back to NAD+ and
• convert pyruvate to ethanol and CO2
Pyruvic acid
Ethanol + CO2
Fermentation in the Human Body
• The capability of different cells/tissues to utilize fermentation
varies in the human body
• Red blood cells do not contain mitochondria, so they rely
exclusively on fermentation.
• Muscle cells can utilize both aerobic and anaerobic respiration for
energy.
• Brain cells are unable to survive long without a constant supply of
blood (e.g., oxygen and glucose) due to their high ATP demand.
• They rely mostly on aerobic respiration.
The effects of five poisons on the electron transport chain and chemiosmosis.
Summary
• Glycolysis is breaks down glucose into two pyruvate molecules
and results in a net gain of two ATP molecules.
• The citric acid cycle is a series of chemical reactions that removes
high-energy electrons that will later be used during the electron
transport chain to generate ATP. One molecule of ATP (or an
equivalent) is produced per each turn of the citric acid cycle.
• The electron transport chain uses chemiosmosis to produce a lot
of ATP.
• In the absence of oxygen, fermentation is used to regenerate
NAD+, ensuring the continuation of glycolysis.
Reproduction and Meiosis
SEXUAL AND ASEXUAL REPRODUCTION
Chapter 9.1 Learning Goals
• Explain the difference between diploid and haploid genomes
• Describe the ways in which homologous chromosomes are very
similar to each other while still having some differences
• Explain the advantages of asexual and sexual reproduction
• Describe the three different life-cycle strategies among sexual
organisms and give example organisms for each
Chromosomes are matched in homologous
pairs
• The somatic (body) cells of each species contain a specific number of
chromosomes; for example, human cells have 46, consisting of 23
pairs of homologous chromosomes.
Openstax: Bioloy Concepts: Figure 7.7. This karyogram shows the chromosomes of a female human immune cell during mitosis.
(credit: Andreas Bolzer, et al)
Chromosomes are matched in homologous
pairs
Homologous chromosomes are
pairs of chromosomes (one
from each parent) that have
the same
• length,
• centromere position, and
• GENES!!!
Keith Chan, Creative
Commons 4.0
Genes and Homologous Chromosomes
Genes are stretches of DNA nucleotides
telling a ribosome how to make a protein
• Each protein controls a trait (eye color,
blood type, etc.)
• Different versions of the trait are
called alleles (brown and blue,
A/B/AB/O)
• Two matched homologues carry the
same genes, but may have different
alleles
Somatic cells (nonreproductive cells) have two sets of
chromosomes (diploid, 2n).
• Matched pairs are called homologous chromosomes.
Gametes (reproductive cells) have one set of chromosomes
(haploid, 1n).
• There are no homologous pairs in a haploid cell.
Life Cycles
An organism’s life cycle is the sequence of stages leading from
the adults of one generation to the adults of the next.
• Each stage of the life cycle will be either diploid (two sets of
chromosomes, 2n) or haploid (one set of chromosomes, 1n)
Animal Life Cycle
• Humans and most other animals are diploid-dominant, because cells
in the multi-cellular body have two full sets of chromosomes (2n).
• Animals are only very briefly haploid when making single-celled
sperm and egg. These cells fuse to make another diploid offspring.
In animals, haploid cells can
never do mitosis. They must
fuse first.
Olaf Oliviero Riemer, Creative Commons 3.0
Animal Life Cycle
Openstax: Biology Concepts, Figure 7.2
Fungus Life Cycle
Fungi are haploid-dominant, because most of their body cells have one
set of chromosomes (1n).
• Two haploid fungi fuse together to make a diploid organism, but then
meiosis occurs soon after to make haploid offspring.
Haploid fungi can do mitosis
and grow bigger!
Caleb Brown. Creative
Commons 3.0.
Fungus Life Cycle
Openstax: Biology Concepts, Figure 7.2
Plant Life Cycle
Plants (and some algae) alternate between multicellular diploid and
multicellular haploid stages.
• This process is called alternation of generations.
• Example, pollen is a multicellular, haploid stage of a flower.
Jessie Eastland, Creative Commons 4.0
Delince.samuel, Creative Commons 4.0
Plant Life Cycle
Steve Thompson, Creative Commons Unported 3.0
Openstax: Biology Concepts, Figure 7.2
Benefits of Asexual Reproduction
Cheaper and Faster
• No need for complicated cell genome changes
(diploid/haploid)
• Can colonize new location as individual
• Can reproduce as fast as can gather resources (no mate)
• All individuals can make babies
Drawbacks of Asexual Reproduction
Less Genetic Diversity
• Offspring are identical clones of parents
• Identical clones are equally unsuited for change in
environment
• Less likely to adapt to new situation; slower evolution
Seedless Fruit Uses Asexual Reproduction
Original Banana Variety was Gros Michel
• Each orchard made by taking cuttings from original tree
(asexual, no mating involved)
• Panama disease (fungus) wiped them out
Replaced by Cavendish Variety
• Also asexual cuttings from tree
• Panama disease starting to adapt . . .
MEIOSIS
Chapter 9.2 Learning Goals
• Define meiosis as a process that converts a diploid cell into 1 or 4
haploid cells
• Explain the differences between meiosis and mitosis
• Describe how the separation of homologous pairs during Anaphase I
converts diploid cells into haploid cells
• Explain the mechanisms within meiosis that generate genetic
variation among the products of meiosis
Gametes
• In animals, gametes (eggs and sperm) are haploid because each cell
has a single copy of each homologous chromosome.
• Gametes fertilize (fuse) to form a zygote, which is now diploid.
• Mitosis of the zygote and its descendants generates all the somatic
cells in the adult form.
Meiosis
• Meiosis is a form of nuclear division that reduces the chromosome
number by half, forming four (or one) haploid cells from a diploid cell.
Homologous
chromosomes
separate
Sister chromatids
separate
INTERPHASE
A pair of
homologous
chromosomes
in a diploid
parent cell
MEIOSIS I
Sister
chromatids
MEIOSIS II
Haploid cells
Stages of Meiosis
Meiosis I:
• First round of nuclear division. Prophase I, Prometaphase I,
etc.
• Reduces number of chromosome sets from diploid to haploid.
Meiosis II:
• Second round of nuclear division. Prophase II, Prometaphase
II, etc.
• Separates sisters. Just like Mitosis. IDENTICAL to Mitosis!
Meiosis I
Prophase I:
• Yada yada chromatin condenses,
spindle fiber forms aaaaaand . . .
• Homologous chromosomes find
each other and swap pieces in a
process called crossing over.
OpenStax: Anatomy and Physiology, Creative Commons 4.0
Meiosis I
Prophase I, cont.:
• Crossing over leads to genetic variation =
genetic recombination (new
combination of genes).
• Recombinant sister chromatid has a
combination of maternal and paternal
genes.
The point of crossing over is to allow for the
genes on the same chromosome to be passed
on in different mom/dad combinations
OpenStax: Biology Concepts, Fig. 7-3
Meiosis I
Prometaphase I:
• Blah blah nucleus dissolves
Metaphase I:
• Homologues align at the cell equator/metaphase plate. For example, in
humans, all 23 homologous pairs line up at the metaphase plate.
• The arrangement of the homologous pairs in meiosis I – metaphase I helps in
the conversion from diploid to haploid.
Independent
Assortment –
Metaphase I
• The orientation of
each pair of
homologous
chromosomes at
the center of the
cell is random:
independent
assortment.
• Second form of
genetic variation.
OpenStax: Biology Concepts, Fig. 7-4
Meiosis I
Anaphase I:
• Homologous pairs separate and move toward opposite poles of
the cell. Diploid → Haploid
• Sister chromatids remain bound together at the centromere.
Telophase I:
• Nucleus reforms (partially).
Male vs. Female Meiosis
In between Meiosis I and II . . .
• Future sperm do a regular Cytokinesis step (i.e. two cells now)
• Future eggs do not do Cytokinesis. They eject one of the two nuclei.
(i.e. still one cell, and one lonely nucleus called a polar body)
https://www.researchgate.net/figure/Polar-body-of-a-mouse-embryo-must-be-properly-oriented-to-avoid-micropipette-penetration_fig1_224166104
Meiosis II
Each of the two haploid products from meiosis I enters meiosis II.
All of Meiosis II
• Same as MITOSIS.
• SISTERS separate
MEIOSIS II
Male vs. Female Meiosis II
After Meiosis II . . .
• Future sperm do another regular Cytokinesis step (i.e. four cells now)
• Future eggs just eject another nucleus (i.e. still one cell, and second
polar body)
https://www.researchgate.net/figure/Following-ICSI-in-our-programme-of-assisted-reproduction-this-oocyte-displayed-a-single_fig1_273466560
Meiosis
Sperm and
Egg
Image from M. Sussman (modified). “Animal Growth and Development.” Prentice-Hall, 1960.
Mitosis and meiosis have important similarities
and differences
Mitosis and meiosis both begin with parent cells that have
chromosomes duplicated during interphase.
• Use spindle fibers for separation
• Same major events
End products differ.
• Mitosis produces two genetically identical somatic daughter
cells.
• Meiosis produces four (or one) genetically unique haploid
cells.
GENDER AND DISORDERS RELATED TO MEIOSIS
Genetic Determination of Gender
– Of 46 chromosomes in fertilized egg, two are sex chromosomes
(other 44 are autosomes)
• X chromosome (large)
• Y chromosome (quite small)
– Females are XX: each ovum always has an X chromosome
– Males are XY: so ~50% of sperm contain X chromosome, and
~50% contain Y chromosome
Genetic Determination of Gender
Development of Homologous Structures of the External Genitalia in both Sexes
Disorders in
Chromosome Number
• Nondisjunction: chromosomes do
not separate normally during
meiosis
• Homologous chromosomes in
Meiosis I
• Sister chromatids in Meiosis II
Down Syndrome (Trisomy 21)
• Down syndrome is an aneuploid
condition that results from three
copies of chromosome 21
Nondisjunction in sex chromosomes
• Can cause abnormalities in sexual and reproductive system
development if occurs with sex chromosomes:
– Turner’s syndrome: females with only a single X chromosome (XO)
never develop ovaries, short
– Klinefelter’s syndrome: males with single Y chromosome and two or
more X chromosomes; are sterile and are normal intellectually; with
more X chromosomes, more risk of intellectual disability
Gender is complicated
• Interferences with normal pattern of sex hormone production in embryo can
result in abnormalities
– If embryonic testes do not produce testosterone, a genetic male develops female
accessory structures and external genitalia
– If genetic female is exposed to testosterone, embryo has ovaries but develops male
ducts, glands, as well as a penis and an empty scrotum
Gender is complicated
▪
Intersex – individuals with reproductive anatomy that differs from typical
female or male anatomy
▪
Due to genetic or hormonal abnormalities
Summary
• Diploid cells contain two sets of chromosomes whereas haploid cells
contain one set.
• Asexual reproduction allows an organism to reproduce itself quickly
without requiring a partner. Sexual reproduction results in genetic diversity.
• There are three main categories of life cycles in multicellular organisms:
diploid-dominant, haploid-dominant, and alternation of generations.
• Meiosis is the form of nuclear division that results in haploid daughter cells
forming from diploid cells. Meiosis also results in genetic diversity due to
crossover and independent assortment.
• Nondisjunction during meiosis can result in disorders.
Patterns of Inheritance
MENDEL’S EXPERIMENTS
Chapter 10.1 Learning Goals
• Explain the scientific reasons for the success of Mendel’s
experimental work
• Describe the expected outcomes of monohybrid crosses involving
dominant and recessive alleles
The science of genetics began in an abbey
garden
• Johann Gregor Mendel (1822-1884) lived in
an abbey in what is now the Czech Republic.
• Supported by the monastery, he taught
physics, botany, and natural science courses
at the secondary and university levels.
• In 1856, he began a decade-long research
project, choosing pea plants as his model
system.
OpenStax: Biology Concepts, Fig. 8-2
In 1866, Mendel published his work and
• correctly argued that parents pass on to their offspring
discrete “heritable factors” and
• stressed that the heritable factors (today called genes)
retain their individuality generation after generation.
A heritable feature that varies among individuals, such as
flower color, is called a trait.
• Each variant for a trait, such as purple or white flowers, is
an allele.
Mendel’s work was unnoticed by the scientific community at first, which
incorrectly believed in the blending hypothesis.
• Continuous variation: a character seen among individuals that has a
wide range of traits, like human height. Bell-shaped curve.
Mendel followed discontinuous variations in his experiments.
• Discontinuous variation: a character seen among individuals where
each individual shows one of two-or a very few-easily distinguishable
traits, like purple or white flowers.
Mendel’s Crosses
• Mendel used garden pea plants
that naturally self-pollinate.
• The result were true-breeding
plants that produce offspring
that look like the parent.
• Prevents appearance of
unexpected traits.
• Mendel used pea plants because
they had a short generation time
and produced large numbers of
offspring.
Jankula00, Creative Commons 4.0
Garden Pea Characteristics
Revealed the Basics of Heredity
• When Mendel crossed contrasting, truebreeding white- and purple-flowered pea
plants, all of the F1 hybrids were purple
• When Mendel crossed the F1 hybrids, many
of the F2 plants had purple flowers, but
some had white
• Mendel discovered a ratio of about three
to one, purple to white flowers, in the F2
generation
OpenStax: Biology Concepts, Fig. 8-3
When the respective male
and female are switched,
Mendel saw the same 3:1
ratio.
• Did not matter which
parent contributed the
trait.
Mendel observed the same
pattern of inheritance in six
other pea plant characters,
each represented by two
traits.
OpenStax: Biology Concepts, Fig. 8-4
Mendel reasoned that only the purple flower
factor was affecting flower color in the F1
hybrids
• Mendel called the purple flower color a
dominant trait and the white flower color a
recessive trait
The recessive trait reappearing in the F2
generation meant that the traits remained
separate (not blended) in the F1 generation.
• Proposed that plants possess two copies of
each trait
• each parent transmits one of their two
copies to their offspring.
OpenStax: Biology Concepts, Fig. 8-3
LAWS OF INHERITANCE
Chapter 10.2 Learning Goals
• Explain the relationship between genotypes and phenotypes in
dominant and recessive gene systems
• Use a Punnett square to calculate the expected proportions of
genotypes and phenotypes in a monohybrid cross
• Explain Mendel’s law of segregation and independent assortment in
terms of genetics and the events of meiosis
• Explain the purpose and methods of a test cross
Genes and Alleles
• What Mendel called a “heritable factor” is what
we now call a gene
• Alternative versions of genes account for
variations in inherited characters
oFor example, the gene for flower color in pea
plants exists in two versions, one for purple
flowers and the other for white flowers
oThese alternative versions of a gene are
called alleles
oEach gene resides at a specific locus on a
specific chromosome
Keith Chan, Creative Commons 4.0
Mendel’s work leads us to two key words
• A genotype is the pair of alleles an organism has for a trait.
• A phenotype is the appearance of the organism for the
trait.
When the two alleles in a genotype are different, only the
dominant one is visible in the phenotype.
A genotype with two of the same allele (two dominant or two
recessive) is called homozygous. Two different alleles is called
heterozygous
• The two alleles at a particular locus may be identical, as in
the true-breeding plants of Mendel’s P generation:
homozygous
• Alternatively, the two alleles at a locus may differ, as in the F1
hybrids: heterozygous
Darryl Leja, Public Domain
OpenStax:
Biology
Concepts, Fig.
8-5
Law of Segregation (Dominance)
If the two alleles at a locus differ (heterozygotes), then one (the
dominant allele) determines the organism’s appearance, and the other
(the recessive allele) has no noticeable effect on appearance.
Homozygous dominant and heterozygous organisms will look identical
(same phenotype, different genotypes).
Monohybrid Cross and the
Punnett Square
• When fertilization occurs between twobreeding parents that differ by the
characteristic being studied it is called a
monohybrid cross.
• The F1 offspring produced in this cross are
monohybrids, heterozygous for one
character.
• A Punnett square is used to predict all
possible outcomes of all possible random
fertilization events.
OpenStax: Biology Concepts, Fig. 8-9
Rules of Probability
• The probability of a specific event is the number of ways that
event can occur out of the total possible outcomes.
• The rule of multiplication calculates the probability of two
independent events both occurring.
• The rule of addition calculates the probability of an event
that can occur in alternative ways.
Rule of Addition – Event Occurring in two or
more alternative ways
Rule of Multiplication – Probability of two
independent events occurring together
Law of Segregation (Passing on)
• States that the two alleles for a gene separate (segregate) during
gamete formation and end up in different gametes.
• This segregation of alleles corresponds to the distribution of
homologous chromosomes to different gametes in meiosis.
OpenStax: Biology
Concepts, Fig. 8-7
Test Cross
• An individual with the dominant
phenotype could be either
homozygous dominant or
heterozygous
• To determine the genotype we can
carry out a testcross: breeding the
mystery individual with a homozygous
recessive individual
• If any offspring display the recessive
phenotype, the mystery parent must
be heterozygous
OpenStax: Biology
Concepts, Fig. 8-8
Law of Independent Assortment
States that each pair of alleles segregates independently of
every other pair of alleles during gamete formation.
This law applies only to genes on different, nonhomologous
chromosomes or those far apart on the same chromosome
(so crossing over can separate).
Genes located near each other on the same chromosome tend
to be inherited together (linkage).
• Can be illustrated by a
dihybrid cross:
• Cross between two truebreeding parents that
express different traits for
two characters.
• 9:3:3:1 ratio seen in F2
(instead of 3:1 ratio).
• In this example,
• A gamete into which an r
allele is sorted could
contain either a Y or y
allele.
• Gives rise to four possible
gamete combinations.
OpenStax: Biology Concepts, Fig. 8-10
Law of independent
assortment can be
seen in meiosis I.
• Crossing over in
prophase I
• Different
homologous pairs
line up in random
orientations during
metaphase I.
OpenStax: Biology Concepts, Fig. 8-11
Frequency of Dominant Alleles
Dominant alleles are not more common in populations than
recessive alleles.
• For example, 1/400 babies in the United States are born with
extra fingers or toes (polydactyly).
• The allele for polydactyly is dominant to the allele for the
trait of five digits per appendage.
https://www.genome.gov/genetics-glossary/Polydactyly
EXTENSIONS OF THE LAWS OF INHERITANCE
Chapter 10.3 Learning Goals
• Explain how heterozygous phenotypes differ in codominance,
incomplete dominance, and multiple alleles.
• Explain how polygenic phenotypes result in continuous traits.
• Explain why recessive, sex-linked phenotypes show up more often in
males than females.
Incomplete Dominance
In incomplete dominance, the
phenotype of F1 hybrids is
somewhere between the
phenotypes of the two
parental varieties.
• Both alleles partially “show
up” in the phenotype of the
heterozygote.
Incomplete dominance in snapdragon color
R1R1
R2R2
R1
R2
R1R2
RudLus02, Creative Commons 4.0
Incomplete dominance in humans:
Hypercholesterolemia
One example of incomplete dominance in humans is
hypercholesterolemia, in which
• LDL receptor (chromosome 19) grabs cholesterol and brings it into
the cell
• Heterozygotes for the mutation have intermediately high
cholesterol levels
• Homozygotes for the mutation have dangerously high levels of
cholesterol in the blood
Codominance
In codominance, both alleles for the
same characteristic are
simultaneously expressed in the
heterozygote.
• Occurs in ABO blood groups of
humans.
• A and B alleles are expressed in
the form of A or B molecules
present on the surface of red
blood cells.
OpenStax: Biology Concepts, Fig. 8-13
Multiple Alleles
Most genes exist in populations in more than two allelic forms.
For example, the four phenotypes of the ABO blood group in humans
are determined by three alleles for the enzyme (I) that attaches A or B
carbohydrates to red blood cells: IA, IB, and i.
• The enzyme encoded by the IA allele adds the A carbohydrate,
whereas the enzyme encoded by the IB allele adds the B
carbohydrate; the enzyme encoded by the i allele adds neither
ABO Blood
Group
OpenStax College, Creative Commons 3.0
Unported
A single character may be influenced by
multiple genes
• Many characters result from polygenic inheritance. Multiple genes
interact to form the phenotype. This is the usual cause for continuous
phenotypes, characteristics with a wide range of outcomes.
• Human skin color is an example of polygenic, incomplete dominant
inheritance.
CKRobinson, Creative Commons
4.0
Sex-Linked Traits
In humans, and other animals and some plants, the sex of the
individual is determined by sex chromosomes (non-homologous
pair).
• A male has XY sex chromosomes, and a female has XX.
X chromosomes have genes for many characters unrelated to sex.
• Genes on the X chromosome are called sex-linked genes
• There are very few genes on the Y chromosome other than
“male factor”
Inheritance of X-Linked Genes
Males cannot be heterozygous for genes on the X
chromosome, since they only have one copy.
• All males are hemizygous for all genes on the X
chromosome.
For a recessive X-linked trait to be expressed
• A male needs only one copy of the recessive allele
• A female needs two copies of the recessive allele, which is
much less common.
Females With
Recessive
Phenotype Are Rare
Even if the mother is
homozygous for the
recessive allele
• Both mother and father
have to pass it on to create
a recessive female
OpenStax: Biology
Concepts, Fig. 8-16
Human sex-linked disorders affect mostly
males
Recessive sex-linked human disorders include
• hemophilia, characterized by excessive bleeding because
hemophiliacs lack one or more of the proteins required
for blood clotting,
• red-green colorblindness, a malfunction of light-sensitive
cells in the eyes, and
• Duchenne muscular dystrophy, a condition characterized
by a progressive weakening of the muscles and loss of
coordination.
Summary
• Mendel postulated that genes (characteristics) are inherited as pairs of
alleles (traits) that behave in a dominant and recessive pattern.
• Alleles segregate into gametes such that each gamete is equally likely to
receive either one of the two alleles present in a diploid individual. In
addition, genes are assorted into gametes independently of one another.
• Alleles do not always behave in dominant and recessive patterns.
• Incomplete dominance describes situations in which the heterozygote
exhibits a phenotype that is intermediate between the homozygous
phenotypes.
• Codominance describes the simultaneous expression of both of the alleles
in the heterozygote.
• Genes that are present on the X but not the Y chromosome are said to be
X-linked, such that males only inherit one allele for the gene, and females
inherit two.
Patterns of Inheritance
MENDEL’S EXPERIMENTS
Chapter 10.1 Learning Goals
• Explain the scientific reasons for the success of Mendel’s
experimental work
• Describe the expected outcomes of monohybrid crosses involving
dominant and recessive alleles
The science of genetics began in an abbey
garden
• Johann Gregor Mendel (1822-1884) lived in
an abbey in what is now the Czech Republic.
• Supported by the monastery, he taught
physics, botany, and natural science courses
at the secondary and university levels.
• In 1856, he began a decade-long research
project, choosing pea plants as his model
system.
OpenStax: Biology Concepts, Fig. 8-2
In 1866, Mendel published his work and
• correctly argued that parents pass on to their offspring
discrete “heritable factors” and
• stressed that the heritable factors (today called genes)
retain their individuality generation after generation.
A heritable feature that varies among individuals, such as
flower color, is called a trait.
• Each variant for a trait, such as purple or white flowers, is
an allele.
Mendel’s work was unnoticed by the scientific community at first, which
incorrectly believed in the blending hypothesis.
• Continuous variation: a character seen among individuals that has a
wide range of traits, like human height. Bell-shaped curve.
Mendel followed discontinuous variations in his experiments.
• Discontinuous variation: a character seen among individuals where
each individual shows one of two-or a very few-easily distinguishable
traits, like purple or white flowers.
Mendel’s Crosses
• Mendel used garden pea plants
that naturally self-pollinate.
• The result were true-breeding
plants that produce offspring
that look like the parent.
• Prevents appearance of
unexpected traits.
• Mendel used pea plants because
they had a short generation time
and produced large numbers of
offspring.
Jankula00, Creative Commons 4.0
Garden Pea Characteristics
Revealed the Basics of Heredity
• When Mendel crossed contrasting, truebreeding white- and purple-flowered pea
plants, all of the F1 hybrids were purple
• When Mendel crossed the F1 hybrids, many
of the F2 plants had purple flowers, but
some had white
• Mendel discovered a ratio of about three
to one, purple to white flowers, in the F2
generation
OpenStax: Biology Concepts, Fig. 8-3
When the respective male
and female are switched,
Mendel saw the same 3:1
ratio.
• Did not matter which
parent contributed the
trait.
Mendel observed the same
pattern of inheritance in six
other pea plant characters,
each represented by two
traits.
OpenStax: Biology Concepts, Fig. 8-4
Mendel reasoned that only the purple flower
factor was affecting flower color in the F1
hybrids
• Mendel called the purple flower color a
dominant trait and the white flower color a
recessive trait
The recessive trait reappearing in the F2
generation meant that the traits remained
separate (not blended) in the F1 generation.
• Proposed that plants possess two copies of
each trait
• each parent transmits one of their two
copies to their offspring.
OpenStax: Biology Concepts, Fig. 8-3
LAWS OF INHERITANCE
Chapter 10.2 Learning Goals
• Explain the relationship between genotypes and phenotypes in
dominant and recessive gene systems
• Use a Punnett square to calculate the expected proportions of
genotypes and phenotypes in a monohybrid cross
• Explain Mendel’s law of segregation and independent assortment in
terms of genetics and the events of meiosis
• Explain the purpose and methods of a test cross
Genes and Alleles
• What Mendel called a “heritable factor” is what
we now call a gene
• Alternative versions of genes account for
variations in inherited characters
oFor example, the gene for flower color in pea
plants exists in two versions, one for purple
flowers and the other for white flowers
oThese alternative versions of a gene are
called alleles
oEach gene resides at a specific locus on a
specific chromosome
Keith Chan, Creative Commons 4.0
Mendel’s work leads us to two key words
• A genotype is the pair of alleles an organism has for a trait.
• A phenotype is the appearance of the organism for the
trait.
When the two alleles in a genotype are different, only the
dominant one is visible in the phenotype.
A genotype with two of the same allele (two dominant or two
recessive) is called homozygous. Two different alleles is called
heterozygous
• The two alleles at a particular locus may be identical, as in
the true-breeding plants of Mendel’s P generation:
homozygous
• Alternatively, the two alleles at a locus may differ, as in the F1
hybrids: heterozygous
Darryl Leja, Public Domain
OpenStax:
Biology
Concepts, Fig.
8-5
Law of Segregation (Dominance)
If the two alleles at a locus differ (heterozygotes), then one (the
dominant allele) determines the organism’s appearance, and the other
(the recessive allele) has no noticeable effect on appearance.
Homozygous dominant and heterozygous organisms will look identical
(same phenotype, different genotypes).
Monohybrid Cross and the
Punnett Square
• When fertilization occurs between twobreeding parents that differ by the
characteristic being studied it is called a
monohybrid cross.
• The F1 offspring produced in this cross are
monohybrids, heterozygous for one
character.
• A Punnett square is used to predict all
possible outcomes of all possible random
fertilization events.
OpenStax: Biology Concepts, Fig. 8-9
Rules of Probability
• The probability of a specific event is the number of ways that
event can occur out of the total possible outcomes.
• The rule of multiplication calculates the probability of two
independent events both occurring.
• The rule of addition calculates the probability of an event
that can occur in alternative ways.
Rule of Addition – Event Occurring in two or
more alternative ways
Rule of Multiplication – Probability of two
independent events occurring together
Law of Segregation (Passing on)
• States that the two alleles for a gene separate (segregate) during
gamete formation and end up in different gametes.
• This segregation of alleles corresponds to the distribution of
homologous chromosomes to different gametes in meiosis.
OpenStax: Biology
Concepts, Fig. 8-7
Test Cross
• An individual with the dominant
phenotype could be either
homozygous dominant or
heterozygous
• To determine the genotype we can
carry out a testcross: breeding the
mystery individual with a homozygous
recessive individual
• If any offspring display the recessive
phenotype, the mystery parent must
be heterozygous
OpenStax: Biology
Concepts, Fig. 8-8
Law of Independent Assortment
States that each pair of alleles segregates independently of
every other pair of alleles during gamete formation.
This law applies only to genes on different, nonhomologous
chromosomes or those far apart on the same chromosome
(so crossing over can separate).
Genes located near each other on the same chromosome tend
to be inherited together (linkage).
• Can be illustrated by a
dihybrid cross:
• Cross between two truebreeding parents that
express different traits for
two characters.
• 9:3:3:1 ratio seen in F2
(instead of 3:1 ratio).
• In this example,
• A gamete into which an r
allele is sorted could
contain either a Y or y
allele.
• Gives rise to four possible
gamete combinations.
OpenStax: Biology Concepts, Fig. 8-10
Law of independent
assortment can be
seen in meiosis I.
• Crossing over in
prophase I
• Different
homologous pairs
line up in random
orientations during
metaphase I.
OpenStax: Biology Concepts, Fig. 8-11
Frequency of Dominant Alleles
Dominant alleles are not more common in populations than
recessive alleles.
• For example, 1/400 babies in the United States are born with
extra fingers or toes (polydactyly).
• The allele for polydactyly is dominant to the allele for the
trait of five digits per appendage.
https://www.genome.gov/genetics-glossary/Polydactyly
EXTENSIONS OF THE LAWS OF INHERITANCE
Chapter 10.3 Learning Goals
• Explain how heterozygous phenotypes differ in codominance,
incomplete dominance, and multiple alleles.
• Explain how polygenic phenotypes result in continuous traits.
• Explain why recessive, sex-linked phenotypes show up more often in
males than females.
Incomplete Dominance
In incomplete dominance, the
phenotype of F1 hybrids is
somewhere between the
phenotypes of the two
parental varieties.
• Both alleles partially “show
up” in the phenotype of the
heterozygote.
Incomplete dominance in snapdragon color
R1R1
R2R2
R1
R2
R1R2
RudLus02, Creative Commons 4.0
Incomplete dominance in humans:
Hypercholesterolemia
One example of incomplete dominance in humans is
hypercholesterolemia, in which
• LDL receptor (chromosome 19) grabs cholesterol and brings it into
the cell
• Heterozygotes for the mutation have intermediately high
cholesterol levels
• Homozygotes for the mutation have dangerously high levels of
cholesterol in the blood
Codominance
In codominance, both alleles for the
same characteristic are
simultaneously expressed in the
heterozygote.
• Occurs in ABO blood groups of
humans.
• A and B alleles are expressed in
the form of A or B molecules
present on the surface of red
blood cells.
OpenStax: Biology Concepts, Fig. 8-13
Multiple Alleles
Most genes exist in populations in more than two allelic forms.
For example, the four phenotypes of the ABO blood group in humans
are determined by three alleles for the enzyme (I) that attaches A or B
carbohydrates to red blood cells: IA, IB, and i.
• The enzyme encoded by the IA allele adds the A carbohydrate,
whereas the enzyme encoded by the IB allele adds the B
carbohydrate; the enzyme encoded by the i allele adds neither
ABO Blood
Group
OpenStax College, Creative Commons 3.0
Unported
A single character may be influenced by
multiple genes
• Many characters result from polygenic inheritance. Multiple genes
interact to form the phenotype. This is the usual cause for continuous
phenotypes, characteristics with a wide range of outcomes.
• Human skin color is an example of polygenic, incomplete dominant
inheritance.
CKRobinson, Creative Commons
4.0
Sex-Linked Traits
In humans, and other animals and some plants, the sex of the
individual is determined by sex chromosomes (non-homologous
pair).
• A male has XY sex chromosomes, and a female has XX.
X chromosomes have genes for many characters unrelated to sex.
• Genes on the X chromosome are called sex-linked genes
• There are very few genes on the Y chromosome other than
“male factor”
Inheritance of X-Linked Genes
Males cannot be heterozygous for genes on the X
chromosome, since they only have one copy.
• All males are hemizygous for all genes on the X
chromosome.
For a recessive X-linked trait to be expressed
• A male needs only one copy of the recessive allele
• A female needs two copies of the recessive allele, which is
much less common.
Females With
Recessive
Phenotype Are Rare
Even if the mother is
homozygous for the
recessive allele
• Both mother and father
have to pass it on to create
a recessive female
OpenStax: Biology
Concepts, Fig. 8-16
Human sex-linked disorders affect mostly
males
Recessive sex-linked human disorders include
• hemophilia, characterized by excessive bleeding because
hemophiliacs lack one or more of the proteins required
for blood clotting,
• red-green colorblindness, a malfunction of light-sensitive
cells in the eyes, and
• Duchenne muscular dystrophy, a condition characterized
by a progressive weakening of the muscles and loss of
coordination.
Summary
• Mendel postulated that genes (characteristics) are inherited as pairs of
alleles (traits) that behave in a dominant and recessive pattern.
• Alleles segregate into gametes such that each gamete is equally likely to
receive either one of the two alleles present in a diploid individual. In
addition, genes are assorted into gametes independently of one another.
• Alleles do not always behave in dominant and recessive patterns.
• Incomplete dominance describes situations in which the heterozygote
exhibits a phenotype that is intermediate between the homozygous
phenotypes.
• Codominance describes the simultaneous expression of both of the alleles
in the heterozygote.
• Genes that are present on the X but not the Y chromosome are said to be
X-linked, such that males only inherit one allele for the gene, and females
inherit two.
Molecular Biology
THE STRUCTURE OF DNA
Chapter 11.1 Learning Goals
• Explain the contributions of Franklin/Wilkins and Watson/Crick to the
discovery of the structure of DNA
• Describe the structure of a DNA monomer, a DNA polymer, and a DNA
double helix
• Explain how hydrogen bonding determines which bases pair up across
the double helix
• Describe how eukaryotic and prokaryotic DNA is arranged in the cell
Discovering the Structure of DNA
• American James D. Watson journeyed to
Cambridge University in England, where the
more senior Francis Crick was studying
protein structure with a technique called Xray crystallography.
• While visiting the laboratory of Maurice
Wilkins at King’s College in London, Watson
saw an X-ray image of DNA produced by
Wilkins’s colleague, Rosalind Franklin.
• Franklin’s picture showed DNA had two
strands and that the sugar-phosphate was
on the outside.
Using Franklin’s data, Watson and Crick
revised their original model that showed
bases on the outside.
In 1962, the Nobel Prize was awarded to
James D. Watson, Francis Crick, and Maurice
Wilkins.
• Rosalind Franklin died from cancer in
1958, so could not receive the prize.
Structure of DNA
DNA and RNA are nucleic acids consisting of long chains
(polymers) of chemical units (monomers) called
nucleotides.
DNA nucleotides are made of three parts:
• Phosphate group
• Nitrogenous bases
• Deoxyribose (5-carbon sugar)
Structure of RNA
RNA is just like DNA except for the following three changes:
• The sugar is in RNA is ribose instead of deoxyribose
• RNA uses a base called Uracil (U) instead of Thymine (T)
• RNA is usually a single strand
How DNA is Arranged in the
Bacterial Cell
A single, circular chromosome must be
compacted to 1/1000th its size
• The large, open circle is pulled
together towards the center,
forming many small loops.
• The loops are supercoiled, causing
them to fold up on themselves.
How DNA is Arranged in the
Eukaryotic Cell
Multiple, linear chromosomes are
protected and packaged to condense
their length to 1/10,000th their size
• DNA is wrapped around histone
proteins to form a nucleosome
• Nucleosomes are stacked to form
coils
• Coils are looped to form supercoils,
similar to those seen in bacteria.
Histone Packaging
https://dnalc.cshl.edu/resources/3d/08-how-dna-is-packaged-advanced.html
DNA REPLICATION
Chapter 11.2 Learning Goals
• Describe DNA replication as a semiconservative process where one
old strand is matched with one new strand in each double helix
• List the four basic steps of DNA replication
• Explain how hydrogen bonding between complementary base pairs
determines which base is added to a new DNA strand
• Describe the three main mechanisms of DNA repair and how they
lower the mutation rate to less than 1 in a billion
• When cells divide, each daughter cell gets
an identical copy of DNA: DNA must be
replicated first
• DNA double helix tells us how DNA is
copied:
• A=T and G=C
• Two strands are complementary to each
other.
• One strand can recreate the other.
• Double helix separates during
replication and each strand serves as
a template.
Semi-conservative Model
• DNA replication follows a
semiconservative model.
• The two DNA strands separate.
• Each strand then becomes a
template for the assembly of a
complementary strand from a
supply of free nucleotides.
• Each new DNA helix has one
old strand with one new
strand.
DNA Replication
Replication of a DNA molecule begins at particular sites called
origins of replication, short stretches of DNA having a specific
sequence of nucleotides.
A protein called Helicase initiates DNA replication by
• attaching to the DNA at the origin of replication and
• separating the two strands of the double helix.
• Form y-shaped structures called replication forks.
Replication then proceeds in both directions, creating
replication “bubbles.”
New DNA
Strand
New DNA
Strand
DNA polymerase only adds nucleotides to an existing strand
• RNA primers used to start these fragments are removed
by an enzyme and DNA ligase fills in the gaps between
these fragments.
The process of DNA replication can be summarized as follows:
1. DNA unwinds at the origin of replication.
2. Primase creates a starting strand of new RNA.
3. New DNA bases are added to the primer and the new strand
begins growing.
4. Primers are removed, new DNA nucleotides are put in place
of the primers and the backbone is sealed by DNA ligase.
https://savi-cdn.macmillanlearning.com/brightcove/index.html?videoId=6196068338001
DNA Repair
DNA polymerase can make mistakes while adding
nucleotides.
• Proof Reading – DNA polymerase can detect incorrect
pairs it has just made and “back up”
• Mismatch repair: enzymes recognize wrong base,
excise it, and replace it with the correct base.
• Nucleotide excision repair:
• DNA double helix is separated
• Incorrect bases removed along with a few other bases
• Replaced by copying the template using DNA polymerase.
Error Rate
The overall error rate after all repair mechanisms is 1 per 2
billion base pairs
• Your genome has 3
billion base pairs.
• You make about 1
COMPLEMENTATION
error/mutation per
round of mitosis.
POLMERASE SELFEDITTING
-7
-10
TRANSCRIPTION
Chapter 11.3 Learning Goals
• Explain the central dogma
• Explain the main steps of initiation, elongation, and termination
• Identify three key differences between DNA replication and RNA
transcription
• Describe the steps of eukaryotic mRNA is processing and the purpose
behind each step
• Avoid key errors related to the central dogma
What is a Gene?
A gene is a stretch of DNA that is transcribed as an mRNA
molecule.
• mRNA molecules will later be translated into proteins.
• rRNA, tRNA, and miRNA will be used as-is.
Proteins translated from mRNA control most features of the
cell.
• An organism’s phenotype comes from proteins, which
come from mRNA, which come from genes.
The Central Dogma
Central Dogma: flow of genetic information
in cells from DNA to mRNA to protein.
• Genes specify the sequences of mRNAs,
• Which in turn specify the sequences of
proteins.
Transcription is the synthesis of RNA under
the direction of DNA.
Translation is the synthesis of proteins under
the direction of mRNA.
DNA
Transcription
RNA
NUCLEUS
Translation
Protein
CYTOPLASM
Transcription: from DNA to mRNA
Bacteria and Eukaryotes perform the same process of
transcription, except:
• Occurs in cytoplasm of bacteria
• Nucleus in eukaryotes, and mRNA transcript must be
transported to the cytoplasm.
In both bacteria and eukaryotes, transcriptions occurs in three
main stages: initiation, elongation, and termination.
Initiation
• DNA double helix partially
unwinds to form a region
called a transcription bubble.
• A promoter is a DNA sequence
onto which proteins (like RNA
polymerase) and enzymes
bind to initiate transcription.
Elongation
• Proceeds from one of the two DNA strands: template strand.
• The mRNA product is complementary to the template strand and is
identical to the other DNA strand (coding strand) except that uracil is
present instead of the thymine.
• RNA polymerase adds nucleotides along the DNA template.
Termination
Bacteria terminate a transcript when a sequence of letters at
the end of the RNA either
• binds to a release protein or
• binds to itself (self-complementing) forming a loop
Eukaryotic termination occurs when
• A sequence of letters in the DNA binds to a release protein or
• A sequence of letters in the RNA binds to a cutting protein
Eukaryotic RNA Processing
Before leaving the nucleus as mRNA, eukaryotic transcripts
undergo RNA processing, in which
• a 5’ cap is added to the beginning of the mRNA. (The cap
prevents it from being degraded and takes it to a ribosome.)
• a poly-A tail is added to the end of the mRNA. (The tail
prevents it from being degraded and takes it out of the
nucleus.)
• introns are removed and exons are stitched together in a
process called splicing
• alternative splicing either leaves an intron in or takes an exon
out, giving you a related (but different) protein
(Alternative Splicing)
https://savi-cdn.macmillanlearning.com/brightcove/index.html?videoId=6196061155001
Differences between DNA Replication and RNA
Transcription
Three key differences between Replication and Transcription
• RNA polymerase doesn’t need a primer
• RNA polymerase doesn’t complement both strands
• Transcribed RNA is immediately removed, allowing the DNA to
come back together.
Key Errors in Molecular Biology
When considering DNA Replication, RNA Transcription, and Protein
Translation, remember the following:
• Replication happens at S phase; Transcription happens in all
phases
• Before you do Translation, you must first do Transcription
• Only about half of Transcription results in an mRNA to be
Translated; the other half of transcribed RNA is used “as-is”
The “Central Dogma”
rRNA, tRNA, and
miRNA
TRANSLATION
Chapter 11.4 Learning Goals
• Describe the Genetic Code as a match between each mRNA codon
and a specific amino acid
• Explain how tRNA complements mRNA to match codons with specific
amino acids
• Describe a ribosome as an enzyme that links amino acids together
after tRNA complements mRNA
The Genetic Code
• The genetic code is the amino acid translations of each of
the nucleotide triplets.
• Three nucleotides specify one amino acid: triplet codon.
• Sixty-one codons correspond to 20 amino acids.
• AUG codes for methionine and signals the start of
translation.
• Three “stop” codons signal the end of translation.
• UAA, UAG, UGA
The Genetic Code
• The genetic code is
• redundant, with more than one codon for most amino
acids,
• unambiguous, in that any codon for one amino acid does
not code for any other amino acid, and
• universal, in that the genetic code is shared by organisms
from the simplest bacteria to the most complex plants
and animals.
The Mechanism of Protein Synthesis
Protein Translation brings together
• One mRNA,
• Two halves of a ribosome, and
• Many different tRNAs, each with one amino acid attached.
Key Point – The tRNAs show up at random until one complements all
three letters of the codon.
• The ribosome can’t actually read message.
• The ribosome can tell when the tRNA makes a proper complement.
“transfer”RNA
• Transfer RNA (tRNA) is one string of RNA,
but it complements itself to make a funky
shape
• Each tRNA has a unique anticodon
matched with a specific amino acid
acceptor
• The whole reason UUC codes for the
amino acid phenylalanine is because the
tRNA with the matching anticodon has
phenylalanine attached.
Phe Codon
Translation
• As the mRNA moves one codon at a time
relative to the ribosome, a tRNA with a
complementary “anticodon” pairs with
each codon
• The ribosome adds the amino acid to the
growing protein chain.
• Stop codons have no matching tRNA, so
the process ends when they appear.
Elongation: Polyribosome arrays
• After a portion of mRNA is “read,” additional ribosomes may attach to already
read part and start another round of translation of same mRNA
•
Polyribosome is a multiple ribosome-mRNA complex that produces multiple copies of same protein
Growing polypeptides
Completed
polypeptide
Incoming
ribosomal
subunits
Ribosomes
Start of
mRNA
Polyribosome
mRNA
End of
mRNA
A polyribosome consists of one strand of
mRNA being read by several ribosomes
simultaneously. In this diagram, the mRNA is
moving to the left and the “oldest” functional
ribosome is farthest to the right.
© 2013 Pearson Education, Inc.
This transmission electron micrograph shows
a large polyribosome (400,0003).
https://savi-cdn.macmillanlearning.com/brightcove/index.html?videoId=6196057789001
Summary: Information transfer from DNA to RNA to polypeptide
DNA
molecule
Gene 2
Gene 1
Gene 4
DNA: DNA base
sequence (triplets) of the
gene codes for synthesis
of a particular
polypeptide chain
mRNA: Base sequence
(codons) of the
transcribed mRNA
tRNA: Consecutive
base sequences of tRNA
anticodons recognize the
mRNA codons calling for
the amino acids they
transport
Polypeptide: Amino acid
sequence of the
polypeptide chain
Triplets
1
2
3
4
5
6
7
8
9
Codons
1
2
3
4
5
6
7
8
9
Anticodon
tRNA
Start
translation
© 2013 Pearson Education, Inc.
Stop;
detach
Summary
• A DNA molecule is double-helix. Each strand is composed of a sugar phosphate
backbone with nitrogenous bases extending from it. The bases of one strand bond
to the bases of the second strand with hydrogen bonds.
• DNA replicates by a semi-conservative method in which each of the two parental
DNA strands act as a template for new DNA to be synthesized.
• Transcription creates RNA from a DNA template. Newly transcribed eukaryotic
mRNA are modified and exported from the nucleus for translation.
• The central dogma describes the flow of genetic information in the cell from
genes to mRNA to proteins.
• Translation is the process of using mRNA to synthesis proteins. The genetic code
is “translated” by the tRNA molecules, which associate a specific codon with a
specific amino acid.
Unit 12: Biotechnology
Introduction
• After the discovery of the structure of DNA, tools were
developed to study and manipulate DNA.
• These advances have led some to refer to the twenty-first
century as the biotechnology century.
• We have seen new applications in medicine, agriculture, and
energy.
• Many of these developments, however, are raising ethical
and social questions.
CLONING AND GENETIC ENGINEERING
Learning Objectives
• By the end of this section, you will be able to:
• Explain the basic techniques used to manipulate genetic
material
• Explain molecular and reproductive cloning
Biotechnology
• Biotechnology is the manipulation of organisms or their components
to make useful products.
• For thousands of years, humans have
• used microbes to make wine and cheese and
• selectively bred stock, dogs, and other animals.
• DNA technology is the set of modern laboratory techniques used to
study and manipulate genetic material.
Manipulating Genetic Material
• To manipulate
nucleic acids,
DNA first needs
to be extracted
from cells.
Polymerase Chain Reaction
• The polymerase chain reaction (PCR) can be
used to amplify a specific sequence of DNA.
• The use of specific primers that flank the
desired sequence ensures that only a
particular subset of the DNA sample will be
copied.
• Starting with a minute sample, automated
PCR can generate billions of copies of a DNA
segment in just a few hours, producing
enough DNA to allow a DNA profile to be
constructed.
Gel Electrophoresis
• Many DNA technology applications rely on gel
electrophoresis, a method that separates macromolecules,
usually proteins or nucleic acids, on the basis of size
• DNA has a negative charge due to the phosphate groups.
• The positive pole of the gel electrophoresis apparatus
attracts the negatively charged DNA.
The analysis of genetic markers can produce a
DNA profile
• DNA technology has rapidly transformed the field of
forensics, the scientific analysis of evidence for crime scene
investigations and other legal proceedings.
• DNA profiling can determine whether two samples of DNA
came from the same individual or whether someone is the
biological parent of a child
DNA Profiling
https://ib.bioninja.com.au/standard-level/topic-3-genetics/35-genetic-modification-and/dna-profiling.html
DNA Profiling
https://ib.bioninja.com.au/standard-level/topic-3-genetics/35-genetic-modification-and/dna-profiling.html
Is this one or two species?
DNA Ladder Lemur 1
Image courtesy Profs. Bostian and Summerill =)
Lemur 2 Lemur 3 Lemur 4
Cloning
• Gene cloning leads to the production of multiple, identical
copies of a gene-carrying piece of DNA in vitro (outside a
living organism) to form a single DNA molecule.
• Reproductive cloning is a method used to make a clone or
an identical copy of an entire multicellular organism.
Molecular Cloning
• Recombinant DNA is formed by joining nucleotide sequences
from two different sources and often different species.
• One source contains the gene that will be cloned.
• Another source is a gene carrier, called a vector.
• Plasmids are small, circular DNA molecules that replicate
separately from the much larger bacterial chromosome; they
are often used as vectors.
Enzymes are used to “cut and paste” DNA
• Restriction enzymes
• recognize a particular short DNA sequence, called a restriction site, and
• cut both strands of the DNA at precise points in the sequence, yielding pieces
of DNA called restriction fragments.
• Once cut, fragments of DNA can be pasted together by the enzyme
DNA ligase.
• Proteins that are
produced from
recombinant DNA
molecules are
called recombinant
proteins.
• https://savicdn.macmillanlearning
.com/brightcove/index
.html?videoId=619606
5654001
New techniques allow a
specific gene to be edited
• The CRISPR-Cas9 system allows
researchers to target a specific gene
in a living cell for removal or editing.
• It is a defense system in bacteria!
• https://www.youtube.com/watch?v=
Kh88cLtlclw
• https://savicdn.macmillanlearning.com/brightco
ve/index.html?videoId=61960678230
01
Reproductive Cloning
• Needs a diploid genetic complement and
an egg cytoplasm.
• Artificially cloned individual: take egg cell
of one organism, remove the haploid
nucleus, and insert a diploid nucleus from a
second organism’s body cell.
• Can also be used to produce embryonic
stem cells
Genetic Engineering
• Genetic engineering involves manipulating genes for
practical purposes by using recombinant DNA technology.
• Scientists have produced many different varieties of
genetically modified organisms (GMOs), organisms that
have acquired one or more genes by artificial means.
• If a gene is transplanted from one organism into another,
typically of another species, the recombinant organism is
called a transgenic organism.
BIOTECHNOLOGY IN MEDICINE AND AGRICULTURE
Learning Objectives
• By the end of this section, you will be able to:
• Describe uses of biotechnology in medicine
• Describe uses of biotechnology in agriculture
Genetic Diagnosis
• The process of testing for
suspected genetic defects
before administering
treatment
• Can be done to determine
the presence or absence of
disease-causing genes in
fetuses.
Gene therapy
• Gene therapy, changing
a defective gene to a
normal one in a living
human
• Could be used to cure
defective genes.
• Relies on using viruses
for introducing the nonmutated gene.
Gene Therapy at Work

Vaccines
https://www.who.int/news-room/feature-stories/detail/the-race-for-a-covid-19-vaccine-explained
Production of Vaccines
• Traditional vaccines = weakened or inactive forms of
microorganisms or viruses
• Vector vaccines = use specific genes of microorganisms
cloned into vectors (a modified version of a different virus)
• Protein based vaccines = use the immunogenic protein parts
of a microorganism
Production of Vaccines
• DNA vaccines
• Genes for viral protein antigens are incorporated into a plasmid
Production of Vaccines
• mRNA vaccines
• mRNA for the viral protein antigen is encased in a lipid nanoparticle
•
https://theconversation.com/what-is-mrna-the-messenger-molecule-thats-been-in-every-living-cell-for-billions-of-years-is-the-key-ingredient-in-some-covid-19-vaccines-158511
Production of Antibiotics
and Hormones
• Bacteria, yeast, cell cultures, and whole
animals can be genetically modified to
make products for medical and other
uses.
• Modified fungal cells produce
antibiotics
• Recombinant DNA technology was used to
produce large-scale quantities of the
human hormone insulin in E. coli as early
as 1978.
Transgenic Animals
• Some proteins used in medicine need a
eukaryotic animal host for proper
processing.
• Transgenic animals = animals
modified to express recombinant
DNA
• Several human proteins are expressed in
the milk of transgenic sheep and goats.
• Ex: a blood anticoagulant protein is
produced in the milk of transgenic
goats.
Figure 12.9 It can be seen that two of these mice are
transgenic because they have a gene that causes
them to fluoresce under a UV light. The nontransgenic mouse does not have the gene that
causes fluorescence. (credit: Ingrid Moen et al.)
Animals can be modified for increased size, etc.
Transgenic Plants
• Manipulating DNA in plants:
disease resistance, herbicide,
pest resistance, nutritional
value, longer shelf life
• Receive DNA from other species
• Monitored to ensure they
are fit for consumption and
don’t endanger other
species (ecologically
stability)
Figure 12.10 Corn, a
major agricultural
crop used to create
products for a
variety of industries,
is often modified
through plant
biotechnology.
Plants can be modified
to be more nutritious
Plants can also be modified to resist insects
without pesticides
Should We Be Worried About GMOs?

Summary
• Nucleic acids can be isolated from cells and then amplified and
separated to perform analysis, such as DNA profiling.
• Cloning may involve cloning small DNA fragments
(molecular cloning) or cloning entire organisms (reproductive
cloning).
• Genetic testing can be performed to identify diseasecausing genes in individuals.
• Vaccines, antibiotics, and hormones are examples of
products obtained by recombinant DNA technology.
• Transgenic organisms possess DNA from different species.

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