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VSU Allergic Reaction Hypersensitivities Case Questions

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BIOL205 – Anatomy and Physiology II
Module 2 – Virtual Assignment 2
Deadline
See Tracking Calendar for due dates.
Directions
For your virtual assignment, please read the case study below and answer the
associated questions.
Janice walks into the ER presenting signs and symptoms of itching and urticaria. She
explains that over the past two days she has had these same symptoms after eating her
morning omelet. Today she started to experience an increase in swelling in her throat,
felt something was not right, and thought it was best to get in to see a doctor
immediately. When filling out her registration forms, she mentioned a familial history
of allergies. The doctor treats Janice with an antihistamine and corticosteroid, and
suggests a follow up with an allergist. He also advises that she should lay off the
omelets and try another breakfast option.
1. Which hypersensitivity disorder does Janice have? Describe the steps involved in
this reaction.
2. What sorts of diagnostic testing might occur? Compare and contrast at least two
methods.
3. Analyze the pathologic process of an anaphylactic reaction. Use this information
to explain the mechanism of action of the emergent treatment required.
4. What are some examples of the types of medications that might be prescribed for
Janice? Describe how they interrupt the pathological process described in
question 1.
5. List and explain some preventative measures that could be taken to prevent
reactions for Janice.
Your answers should be approximately 500 words and follow APA format: include a
title page, 1”margins, 12-point font, double spaced, APA citations and reference page.
See the grading rubric below.
BIOL205 – Virtual Assignment 2
2
BIOL205 – Virtual Assignment 2 – Grading Rubric
Criteria
Content
80 points
Spelling, Grammar,
Mechanics
10 points
Research, Citations,
and APA Format
10 points
Instructor
Comments:
Exceeds Expectations
Meets Expectations
Needs Improvement
72-80 points
56-71 points
0-55 points
The project covers all required
content appropriately and accurately;
shows full understanding of the
content and overall biology.
1 area of content was not covered
appropriately or adequately; shows
partial understanding of the content
and overall biology.
2 or more areas of content were not
covered appropriately or adequately;
shows minimal understanding of the
content and overall biology.
9-10 points
7-8 points
0-6 points
0-1 spelling/grammar errors. Project
is free of errors in areas of spelling,
grammar, and punctuation. The
project is fully easy to read and
understand.
2 -3 spelling/grammar errors. Project
contains some errors in spelling,
grammar, and punctuation. The
project is mostly easy to read and
understand.
4 or more spelling/grammar errors.
Project contains significant errors in
spelling, grammar, and punctuation
making the project difficult to read
and/or understand.
9-10 points
7-8 points
0-6 points
0-1 APA errors. Demonstrates
excellent understanding of
information literacy to evaluate,
interpret and integrate research from
outside resources. APA format is
fully applied to in-text citations and
references.
2-3 APA errors. Demonstrates
adequate understanding of
information literacy to evaluate,
interpret and integrate research from
outside sources, but may contain
some minor errors. APA format is
mostly applied to in-text citations and
references.
4 or more APA errors. Does not
demonstrate understanding of
information literacy to evaluate,
interpret and integrate research from
outside sources. May contain
significant APA errors. APA format is
not applied to in-text citations and/or
references.
Total
Points:
Points
Lecture 2 – Immune and Genetic
Disorders
BIOL205
Lesson 1 – The Immune System
Introduction
With a clear understanding of the role of cells in disease, in this lecture, we’ll consider
some specific etiologies of disease: diseases related to our immune system and genetic
disorders.
The immune system is a complex multi-component system that functions throughout
the body to protect against invading pathogens or foreign agents as well as internal
cells that pose threats, such as cancer cells. Pathogens are microbes, such as bacteria,
viruses, or protozoa that cause human disease. We’ll first do a basic recap on normal
immune function before exploring ways that the immune system can contribute to
disease.
Inclusion of Theory
As we discuss the immune system, we’ll break it down into three lines of defense.
While discussed separately, these all actually are working together to protect the body.
The lines of defense are described below.
1. First line of defense: The first line consists of barriers, such as the skin and
mucous membranes, that prevent pathogens from even entering the body.
2. Second line of defense: The second line consists of a variety of body processes
that work in various ways to destroy any pathogen. We will examine cells,
chemicals, and some processes that are part of the second line of defense.
3. Third line of defense: The third line consists of particular types of lymphocytes
that act against specific targets to destroy the pathogen. Once these lymphocytes
have encountered their particular pathogen to combat, there is a memory system
that allows these cells to react more quickly and strongly the next time the
pathogen is encountered. This is why we typically don’t get the same infection
twice, and also the foundation for the action of vaccines.
With these concepts in mind, let’s explore innate immunity first. Recall that these topics
were covered in detail in pre-requisite classes, so we’ll provide just an overview here.
BIOL205 – Lecture 2
2
Subject 1: Non-specific Immunity
In terms of body defenses, the first two lines of defense are considered non-specific or
innate. This means that these act equally well against any pathogen and we are born
with them working well. They do not discriminate between particular pathogens and
they respond quickly after exposure.
The first line of defense consists of barriers to entry: physical and biochemical barriers
are found in skin and mucous membranes.
(Sorenson et al. 2019, Figure 13.9)
The second line of defense is also innate or non-specific and it consists of cells,
chemicals, and processes that act on any pathogen equally well. The innate immune
system has the ability to recognize structures that are highly conserved on many
microbes called pathogen-associate molecular patterns (PAMPs).
Various components of the innate immune system are detailed in the table below. These
and other components of the innate immune system will be described briefly below.
BIOL205 – Lecture 2
Component
Anatomic, mechanical, and
chemical barriers
Phagocytic cells
Cells that release
inflammatory mediators
Lymphocytes
Molecules of innate
immunity
3
Examples
Skin, flow of air or fluids, salivary lysozyme, fatty
acids of the skin, antimicrobial peptides
Polymorphonuclear leukocytes, monocytes, and
macrophages
Basophils, mast cells, and eosinophils
Natural killer cells
Complement proteins, acute-phase proteins
(Sorenson et al. 2019, Table 13.6)
Phagocytic Cells
Macrophages and neutrophils (also known as polymorphonuclear leukocytes or PMNs)
conduct phagocytosis to destroy pathogens and debris in the body.
Natural Killer (NK) Cells
These are a type of lymphocyte that patrols the body looking for diseased body cells
that don’t look “right” by assessing certain proteins that are on the surface of all human
cells. Cells that have been infected with a virus or bacterium, or cells that have turned
cancerous will fall in this category of diseased cells and the NK cells will bind to them
and release chemicals that cause the diseased cell to burst, resulting in cell death.
NIAID. (2016, November 2). Natural Killer cells [Illustration]. National Institute of Allergy and Infectious
Disease. https://commons.wikimedia.org/wiki/File:Natural_Killer_Cell_(30439199790).jpg
BIOL205 – Lecture 2
4
Other Immune Cells
Circulating leukocytes, such as basophils and eosinophils, as well as tissue resident
mast cells are filled with chemical-containing granules that release inflammatory
mediators when they are activated. These inflammatory mediators, known as cytokines,
help facilitate the immune process, trigger inflammation, and allow immune cells to
communicate with one another.
Interferons
Interferons are a group of proteins that are released from cells that have been infected
by a virus, and they diffuse to other nearby cells to signal these cells to employ cellular
defenses that inhibit the viruses from replicating inside the cells. In addition, interferons
call nearby NK cells to destroy infected cells. Interferons have been used in cancer
therapy to help kill cancer cells.
Complement Proteins
Another set of chemicals that are important in immunity are the complement proteins,
named because they complement the immune response. These are a series of chemicals
that are turned on as a cascade (like the clotting cascade) and they help destroy
pathogens in a number of ways: increasing inflammation; stimulating phagocytosis;
lysis of pathogen cells and removal of antigen-antibody complexes. Complement
deficiencies are disorders that increase the risk of infectious disease.
Inflammatory Process
Inflammation is defined as the body’s non-specific response to tissue injury. This
process occurs any time there is an injury, and the purpose of it is to begin the healing
process and prevent infection. We will discuss this in detail later in the lesson.
Fever
A fever is an elevation in body temperature initiated by infection, trauma, or drug
reactions. Chemicals called pyrogens trigger a change in the body temperature set point
in the hypothalamus. Fever helps the body fight infection by slowing the rate of
reproduction of viruses and bacteria, by promoting interferon activity, and by speeding
up the body’s metabolic and tissue repair rates.
Please watch the following 3 minute, 13-second video by AMBOSS: Medical Knowledge
Distilled. The video reviews the roles of the innate immune system. As you watch the
video:
• Note the steps of the immune response.
Click the following link to watch:
Innate and Adaptive Immunity: Types of Immune Responses (Short version)
BIOL205 – Lecture 2
5
AMBOSS: Medical Knowledge Distilled. (2020, December 17). Innate and Adaptive Immunity: Types of
Immune Responses (Short version) [Video]. YouTube.

Video Takeaways
The video reviews the steps in an immune response starting with barrier functions of
skin and mucous membranes, and moving on to inflammation, white blood cells,
recognition of PAMPs, phagocytosis, and the role of complement.
Subject 2: Specific Immunity
The third line of defense is called specific or adaptive. This is because there are specific
lymphocytes that have the potential to respond to specific pathogens. So there are
lymphocytes that specifically recognize the influenza virus (that causes the flu), while
other lymphocytes recognize other pathogens. As described above, this specific
recognition is the basis of immune memory, which protects the body against
subsequent infection with the same pathogen. Thus, adaptive immunity adapts to what
an individual has encountered. In addition, the adaptive immune response is “trained”
to not recognize “self” antigens, so individuals should have self-tolerance. This process
goes awry in auto-immune disorders.
There are two “arms” of the adaptive immune response that work together to defeat
pathogens. The first is cellular (or cell mediated) immunity. This works against
pathogens that are inside cells or diseased cells themselves by destroying the infected or
diseased cell. This allows us to fight viruses or intracellular bacteria that infect us.
Cellular immunity is also effective against parasitic worms, cancer cells and (in some
cases) cells that have been transplanted and are thus foreign.
The other arm of adaptive immunity is the humoral or antibody mediated response.
(The word “humoral” is an old term that relates to the body “humors” or fluids. In this
case we mean blood and lymph). Humoral immunity is carried out by antibodies that
circulate in the blood and attack extracellular microbes and other foreign entities such
as toxins or venoms that exist outside of cells.
The diagram below depicts the adaptive immune response. Please review in order to
have a solid grasp of the process before proceeding.
BIOL205 – Lecture 2
6
(Sorenson et al. 2019, Figure 13.8)
The key weapon of humoral immunity is the production of antibodies by plasma cells.
There are five different classes of antibodies, named with different letters, and they
have slightly different configurations and functions. Antibodies are immune globulins,
abbreviated Ig. Please review the structures and function of IgG, IgM, IgE, IgD, and IgE
in the table below.
BIOL205 – Lecture 2
7
Classes of Antibodies. (n.d.). [Image]. BC Campus. https://opentextbc.ca/biology/chapter/23-3antibodies/
When a person is exposed to a pathogen or antigen for the first time, the immune
response is called a primary response, and, based on the steps involved, it takes a few
days to mount a response. During this time, the pathogen has had time to cause an
infection and make you sick. However, we know that there is immune memory and that
memory T and B cells are created after that first exposure. So, upon subsequent
exposure, a secondary response is deployed that is faster and more robust than the
primary response. It’s so quick that the pathogen does not have time to make you sick
before it is defeated, and no illness develops.
When we measure the concentration of antibody in the blood, that’s called a titer.
Antibody levels may be measured in clinical situations to determine whether a person
has immunity to a particular pathogen. Antibody titers for a primary and secondary
response to a generic antigen are indicated in the graph below.
BIOL205 – Lecture 2
8
Connexions. (2013, September 6). Primary and Secondary Immune response [Image]. Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:2223_Primary_and_Secondary_Antibody_Respons_
new.jpg
The table below summarizes the key features of innate and acquired immunity.
Table 11.1 Characteristics of Innate and Acquired Immunity
Characteristics
Innate Immunity
Acquired Immunity
Line of defense
First line of defense
Second line of defense
Timing of
Immediate response
Delay between exposure to antigen
defense
and response. Can take days to
weeks. Once acquired immunity is
developed to a specific antigen has
developed, response is immediate.
Specificity
Broad
Specific response to specific antigen
Memory
No memory involved
Memory involved
Cells involved
Mast cells, granulocytes
T and B lymphocytes,
(neutrophils, eosinophils,
macrophages, dendritic cells
basophils), monocytes,
macrophages, natural killer
cells, platelets, endothelial
cells
(Sorenson et al. 2019, Table 11.1)
With a review of immunity complete, let’s now consider the inflammatory process.
Lesson 1 Completed!
Thank you! You have completed this lesson. Please scroll down to complete a short,
ungraded Knowledge Check activity.
Check Your Knowledge 1
BIOL205 – Lecture 2
9
Drag and Drop
Place each term in the proper category to indicate the correct line of defense.
First line of defense
Skin
Barriers
Mucous membranes
Second line of defense
Interferon
Complement
NK cells
Neutrophils
Macrophages
Fever
Inflammation
Third line of defense
T lymphocytes
B lymphocytes
Antibodies
Immune memory
Primary and secondary
response
Lesson 2 – Focus on Inflammation
Introduction
As noted above, inflammation is the body’s non-specific response to tissue injury, and it
functions as part of the second line of defense. The purpose of inflammation is to
elimiate the cause of injury, remove dead cells, initiate an immune response if needed,
and begin tissue repair.
The word, inflammation, is from the Latin meaning “to set on fire.” Inflammatory
processes within the body tend to end with the suffix “-itis,” so appendicitis,
pharyngitis, arthritis, pleuritis, all indicate inflammation. It should be noted that
inflammation is not the same as infection, which means that the body has been invaded
by a pathogen. Inflammation can occur during infection but also occurs with other
types of injury.
There are two main categories of inflammation that we will explore: acute and chronic.
Table 11.2 Characteristics of Acute and Chronic Inflammation
Feature
Acute Inflammation
Chronic Inflammation
Onset and
Fast onset (minutes to hours)
Slow onset: over days to weeks
duration
and relatively short duration
and lasting at least 2 weeks
Cellular infiltrate 1 Neutrophils
1 Monocytes
1 Macrophages
1 Lymphocytes
Degree of tissue
Usually mild and self-limiting
Persistent and progressive
injury
Predominant
Vascular and exudative
New connective tissue
process
formation
Local and
Prominent
Less severe
systemic signs
(Sorenson et al. 2019, Table 11.2)
BIOL205 – Lecture 2
10
Subject 1: Acute Inflammatory Response
Acute inflammation has a quick onset, and in addition to the local response, may have
prominent systemic signs. Tissue injury, infection, reaction to a foreign body, and
immune reactions are examples of situations where acute inflammation may occur.
Please watch the following 2 minute, 53 second video by Adriana Lippy to visualize the
process of acute inflammation. As you watch the video, consider the following:
• Define the following terms: vasodilation, margination, endothelial contraction,
diapedesis, and chemotaxis.
• List the four cardinal signs of inflammation with their causes.
Click the following link to watch:
Acute Inflammation – Educational 3D Animation
Lippy, A. (2016, August 23). Acute Inflammation- Educational 3D Animation [Video]. YouTube.

Video Takeaways
Vasodilation of local arterioles is due to histamine and nitric oxide. As blood flow
slows, leukocytes can move to the sides of the vessel, called margination. Endothelial
contraction leads to increased permeability of the vessels, causing them to leak fluid. As
the leukocytes roll along the margins of the vessel, they will eventually squeeze out into
the tissue in a process called diapedesis. Once out of the bloodstream, they follow the
chemical gradient to reach the site of injury, in a process called chemotaxis.
(Sorenson et al. 2019, Figure 11.4)
The four cardinal signs of inflammation are heat and redness (due to vasodilation),
swelling (due to increased capillary permeability) and pain (due to chemical
mediators/cytokines).
BIOL205 – Lecture 2
11
(Sorenson et al. 2019, Figure 11.3)
At the site of injury, neutrophils, who are the first responders, destroy the pathogen as
well as injured tissue via phagocytosis.
(Sorenson et al. 2019, Figure 11.5)
As is evident, there are numerous cell types involved in acute inflammation.
BIOL205 – Lecture 2
12
(Sorenson et al. 2019, Figure 11.6)
Inflammatory Cells
Platelets are formed elements of the blood that contribute to the clotting process.
Neutrophils and macrophages are actively phagocytic, with neutrophils arriving first,
and macrophages arriving later to clean up. (Some tissues also have tissue resident
macrophages.) Recall that monocytes are leukocytes that turn into macrophages. The
final cells are mast cells: these are tissue resident cells that are found in portals of entry
that release a wide variety of chemical mediators that cause inflammation.
Inflammatory Mediators
There are a number of chemical mediators of inflammation. Cell-derived mediators can
be secreted from stored granules, or created once inflammation starts. Other mediators
are produced from plasma proteins and include the complement system (discussed
above), the coagulation system (for blood clotting), and a kinin system (which interacts
with and helps regulate the inflammatory process).
Termination of inflammation: There are a variety of normal body anti-inflammatory
processes that help bring a halt to this process. One of the most important of these is the
hypothalamic-pituitary-adrenal (HPA) axis via the production of cortisol, which is an
anti-inflammatory agent.
BIOL205 – Lecture 2
13
(Sorenson et al. 2019, Figure 11.8)
Morphology of Inflammation
There are four basic types of acute inflammation with exudate (fluid in the interstitial
space):
1. Serous inflammation: clear, watery exudate (example, blister)
2. Fibrinous inflammation: thicker exudate with some protein
3. Purulent inflammation: contains pus (example, abscess)
4. Ulceration: contains necrotic tissue
Systemic Manifestations of Inflammation
While inflammation is local, the cytokines produced may initiate a systemic response to
inflammation called an acute phase response. Certain manifestations are typical:
1. Fever
2. An increase in certain serum proteins that cause two important clinical signs.
• C-reactive protein (CRP) is made by the liver and increases non-specifically
during inflammation. Lab tests can assess for elevated CRP.
• Increased erythrocyte sedimentation rate (ESR) which means that
erythrocytes settle more quickly in solution due to excess fibrinogen.
Increased ESR is also an important lab test for systemic inflammation.
• Leukocytosis, or increased levels of white blood cells. The normal range is
around 5000- 10,000 cells/uL and elevations may indicate infection. A
BIOL205 – Lecture 2
14
differential white blood cell (WBC) count (where relative percentages of
WBCs are assessed) may help determine the particular cause of inflammation
or infection.
Outcomes of Acute Inflammation
Acute inflammation may result in resolution and complete healing. However, there
may be fibrosis formation and scarring if there is significant tissue damage.
Occasionally an abscess (pus-filled cavity) will occur. Finally, chronic inflammation
may occur, and that is the next topic.
(Sorenson et al. 2019, Figure 11.9)
Subject 2: Chronic inflammation and disease
Chronic inflammation is defined as persisting for at least two weeks and is
characterized by higher levels of lymphocytes, macrophages, and monocytes. Signs and
symptoms are less severe than acute inflammation, and it’s less common that there is a
systemic response. It may follow an acute inflammation that does not resolve or
develop independently.
Here are three potential causes:
1. Unresolved or repeated acute infections, due to particular pathogens that are
difficult to eliminate.
BIOL205 – Lecture 2
15
2. Autoimmune disease due to inappropriate activation of the immune system to
self-antigens.
3. Prolonged exposure to irritants.
Please watch the following 1 minutes, 34-second video by Criticalbench to review
information on chronic inflammation and disease.
Click the following link to watch:
Chronic Inflammation: The Root Cause of a Multitude of Diseases
Criticalbench. (2014, January 13). Chronic Inflammation: The Root Cause of a Multitude of Diseases [Video].
YouTube. https://www.youtube.com/watch?v=GTu7KUXOr-U&feature=youtu.be
Video Takeaways
As discussed in the video, chronic inflammation has been linked to numerous diseases.
We’ll cover more about many of these disorders as we move through the class, but here
is a brief list of some conditions.
Disease
Alzheimer’s
Asthma
Atherosclerosis
Cancer
Obesity
Information
A type of dementia with neuroinflammation in the brain
Respiratory disorder with chronic airway inflammation
Chronic inflammation where leukocytes damage blood
vessels
Chronic inflammation of tissue can trigger changes that
lead to neoplasia.
Adipose tissue secretes cytokines that can be associated
with inflammation.
For both acute and chronic inflammation, there are a variety of anti-inflammatory
medications available, as listed in the table below.
Table 11. 6 Common Medication Used to Treat Inflammation
BIOL205 – Lecture 2
Actions
16
Aspirin
Acetaminophen
NSAIDs
Cyclooxygenase
Inhibitors

Prednisone
Antiinflammatory
Analgesic
Antiinflammatory
Antiinflammatory
Antiinflammatory
Analgesic
Analgesic
Analgesic
Antipyretic
Antipyretic
Antipyretic
Delays blood
clotting
May increase
risk for heart
disease
Suppresses
immune
system
Should not be
used in people
allergic to
sulfonamides
Increased
risk of
infection
Increased
blood
pressure and
edema
Antipyretic
Precautions
Alters blood
clotting and
increases risk
for bleeding
May damage
kidney and/or
liver in high
doses
Should not
be given to
children
Medications
That Target
Specific
Mediators
Used for
more serious
types of
inflammation
such as
rheumatoid
arthritis (e.g.,
adalimumab)
Increase risk
of
developing
lymphoma
Should not
be used if
infection is
present such
as
tuberculosis
Osteoporosis
and skeletal
wasting with
long-term
use
(Sorenson et al. 2019, Table 11.6)
Lesson 2 Completed!
Thank you! You have completed this lesson. Please scroll down to complete a short,
ungraded Knowledge Check activity.
Check Your Knowledge 2
In each statement below, correct what is incorrect:
1. The four cardinal signs of inflammation are redness, swelling, heat and itching.
(pain)
2. Neutrophils and platelets are actively phagocytic. (macrophages)
3. Thyroxine, from the HPA axis, is an anti-inflammatory. (cortisol)
4. Serous inflammation contains pus. (purulent)
5. During inflammation levels of CRP decrease. (increase)
6. Atherosclerosis can result from acute inflammation. (chronic)
Lesson 3 – Immune System Disorders
Introduction
A properly functioning immune system protects well from pathogens and cancer.
However, the immune system can malfunction, and this can lead to disease. Immune
BIOL205 – Lecture 2
17
system disorders fall into three main groups: too much immunity that is destructive,
known as hypersensitivity; misdirected immunity (autoimmunity); and decreased
immunity or immune deficiency disorders. We’ll consider these three types with some
particular disease examples.
Subject 1: Hypersensitivities
Hypersensitivities result from inappropriate activation of the immune system, and they
fall into four main types, based on the factor involved and time frame of response. The
acronym, “ACID” is helpful in remembering which is which.
Type
Type I
Type II
Type III
Type IV
Acronym
Allergy
Cytotoxic
Immune complex
Delayed type
Description
IgE mediated allergy
antibody mediated cytotoxic reactions
complement mediated immune complexes
delayed type T cell mediated disorders
Type I
These reactions occur immediately and are known as allergic reactions. In this case, the
antigen recognized by the immune system is known as an allergen. There are many
common allergens in the environment, such as pollen, ragweed, dust, pet dander, foods,
etc. and the location of where the allergic reaction takes place (skin, lungs, etc.) will
influence the response. In certain cases, an allergic reaction may lead to anaphylaxis,
which is a life-threatening event – more on that later.
The cellular process is outlined here:
BIOL205 – Lecture 2
18
(Sorenson et al. 2019, Figure 14.4)
The first stage is the sensitization stage, and it happens with the first exposure to the
allergen. In this step, the allergen enters the body, and the body mounts an immune
response, leading to antibody production from plasma cells. One of the antibodies, IgE,
binds to tissue resident mast cells and this is what we call sensitization. Please note that
there is no allergic response with first exposure. Upon second and subsequent
exposures, the allergen enters the body and can now bind to the IgE on the mast cells,
which triggers the mast cells to release their granular contents of histamine and many
other chemicals. These chemicals lead to the primary response (initial-phase response)
which is an inflammatory response in the tissue. It includes vasodilation, fluid leakage
from vessels, and smooth muscle contraction, and these responses cause the effects of
an allergic reaction. Subsequent to this the late phase response occurs hours later and
may last for days. This response includes more tissue infiltration with leukocytes.
BIOL205 – Lecture 2
19
Manifestations of a Type I hypersensitivity reaction may be in the form of hives, nausea
and vomiting for GI allergens, or perhaps a runny nose in the case of allergic rhinitis.
These may be treated with anti-histamines. There may be a genetic component to
having an increased risk of hypersensitive reactions. It is not uncommon for an
individual to be “allergy-prone” and some folks who have seasonal or food allergies
may also have eczema and or asthma, both of which are Type I hypersensitivity
reactions.
Anaphylaxis is a severe life-threatening systemic hypersensitivity reaction. The two
most critical manifestations are widespread vasodilation, leading to shock (which
means a very low blood pressure), and constriction of airways leading to difficulty
breathing. Treatment for anaphylaxis requires medicine to reverse these two effects.
Epinephrine is an adrenergic agent that vasoconstricts and bronchodilates, thereby
raising blood pressure and opening airways to improve breathing. This is quickly and
efficiently administered via epi-pen.
Tokyogirl79. (2016, August 23). Epi-pen [Image]. Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:Epi-Pen_2016.jpg
In addition, it is important to administer anti-histamine to block the ongoing process.
Diagnosis of Type I hypersensitivities may be done in numerous ways. There are a
couple of methods that involve intentional exposure to the allergen in order to measure
a response. Another way is to take a blood sample and measure the levels of IgE to
particular allergens.
Please review the following 1 minute, 36-second video by HAL Allergy Group and
review the concepts involved in diagnosing an allergy.
Click the following link to watch:
How to diagnose an allergy?
HAL Allergy Group. (2015, February 10). How to diagnose an allergy? [Video]. YouTube.


An image of allergy skin testing is below.
BIOL205 – Lecture 2
20
(Sorenson et al. 2019, Figure 14.5)
Prevention of allergic reactions may involve avoidance of the allergen (particularly for
food allergies). In addition, some patients may receive allergy shots, which expose to
very small but increasing doses of the allergen in order to desensitize the person to the
response.
Treatment of allergy involves anti-histamines, as described above. There are also drugs
that can stabilize mast cells. Emergent treatment for anaphylaxis requires epinephrine.
Type II
Type II reactions are what are termed “cytotoxic,” meaning that they are toxic or
damaging to whole cells. These are antibody-mediated responses (IgG or IgM) directed
against target antigens on cell surfaces. The cellular process is as follows:
BIOL205 – Lecture 2
21
(Sorenson et al. 2019, Figure 14.6)
An antigen is present on the surface of a cell, and there are antibodies produced against
the antigen. When the antibodies bind to the cell surface antigens, this brings about
destruction of the targeted cell in a variety of ways.
One example of a Type II hypersensitivity is a mismatched blood transfusion reaction,
whereby antibodies to the non-compatible blood type bring about destruction of the
transfused blood cells. A second example is in the case of Graves disease, an
autoimmune disease where the antibody is directed against self TSH receptors on the
thyroid gland, triggering excess release of thyroid hormone leading to hyperthyroidism.
Type III
Type III hypersensitivity reactions are when insoluble antigen-antibody complexes
deposit in tissues and trigger an inflammatory response.
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(Sorenson et al. 2019, Figure 14.7)
Damage occurs when the complexes are deposited within the blood vessels or tissues
and inflammatory cells infiltrate. This process can cause damage to the glomeruli in the
kidneys, the lungs, and joint synovium.
Please watch the following 3 minute, 15-second video by AMBOSS: Medical Knowledge
Distilled, which depicts Type III hypersensitivity reactions and compares them to Type
II.
Click the following link to watch:
Immune Complex-Mediated Hypersensitivity: Type III Hypersensitivity Reaction
AMBOSS: Medical Knowledge Distilled. (2019, January 29). Immune Complex-Mediated Hypersensitivity:
Type III Hypersensitivity Reaction [Video]. YouTube.

Type III hypersensitivities are responsible for the vasculitis seen in some autoimmune
disorders, as well as the kidney damage seen in acute glomerulonephritis. Serum
sickness is a disorder that occurs when the immune system reacts to medicines that
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contain foreign proteins. It can be caused by various antibiotics, other drugs, certain
foods, and insect venom. Symptoms include fever, rash, and arthritis.
Type IV
Type IV reactions are different from the first three because they involve T cell activation
(rather than antibodies), and thus take longer to develop.
(Sorenson et al. 2019, Figure 14.8)
One of the most well-known examples of a Type IV hypersensitivity reaction is a
tuberculin test (PPD). In this test, the tuberculosis (TB) antigen is injected under the skin
and the results are read in 48 hours: a skin reaction indicates that the individual has
mounted an immune response against tuberculosis.
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CDC. (n.d.). TB skin test [Image]. CDC.
https://www.cdc.gov/tb/webcourses/course/chapter3/3_testing_for_tb_disease_and_ltbi_3_m
antoux_tuberculin_skin_test_reading_the_tst_induration.html
Another example is sensitivity to poison ivy. The urushiol oil in poison ivy can cause a
Type IV hypersensitivity reaction that develops days after exposure.
This table summarizes the four types of hypersensitivity reactions.
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OpenStax. (n.d.). Hypersensitivity [Image]. Wikimedia Commons.
https://en.wikipedia.org/wiki/Hypersensitivity
Subject 2: Autoimmunity
The next general category of immune system disorder is autoimmunity. This occurs
when the body reacts inappropriately to a self-protein that should be tolerated. As
indicated above, these reactions may occur as a hypersensitivity reaction, but against
self. These conditions are a failure of the self-tolerance that should be part of the
immune system.
The causes of autoimmunity are not entirely clear, but it is evident that a couple of
factors may play a role, including genetic predisposition, environmental factors, and
gender. In terms of genetic predisposition, a family history of any auto-immune
disorder may predispose an individual to develop one; however, it is likely a trigger
event, as not everyone who is pre-disposed develops an auto-immune disorder. Trigger
events may include environmental exposure to various pathogens or chemicals, or some
sort of unmasking of a self-antigen within the body.
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Please watch the following 3 minute, 3-second video by Yahoo Life that provides some
information on autoimmune disorders: As you watch the video, consider the following:
• What are some examples of autoimmune diseases?
• What are some common manifestations of most autoimmune disorders?
• Which gender is at greater risk of getting an autoimmune disease?
Click the following link to watch:
This is what happens when you have an autoimmune disease
Yahoo Life. (2018, August 10). This is what happens when you have an autoimmune disease [Video]. YouTube.

Video Takeaways
There are a number of autoimmune diseases, and some of the more well known ones
include rheumatoid arthritis, Type I diabetes, lupus, celiac disease, Hashimoto’
thyroiditis and multiple sclerosis. Many autoimmune disorders have some similar signs
and symptoms, including fatigue, muscle aches, fever, depression, and inflammation, in
addition to specific manifestations related to the organ involved. Overall, autoimmune
diseases are more common in women than in men.
Autoimmune diseases may exhibit remissions and exacerbations, typically based on
stress. Diagnosis of an autoimmune disease can be tricky and take time. Treatment may
involve organ specific remedies, and also overall means to reduce the immune
response, such as steroidal and non-steroidal anti-inflammatory agents. In addition,
plasmapheresis, a technique whereby antibodies are removed from plasma and the
plasma is reinfused, may be employed.
Lupus
Systemic Lupus Erythematosus (SLE, or Lupus) is a chronic systemic autoimmune
disease that we’ll examine more closely as an example of the disease process.
Etiology
The etiology of lupus is autoimmune, but the exact causes are not known. It is more
common in women than men and typically presents between ages 15 and 44.
Individuals of African and Asian descent more commonly develop lupus. In general,
the disease process involves immune complex deposition and inflammation of various
organs of the body.
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(Sorenson et al. 2019, Figure 14.10)
Manifestations
Manifestations of lupus occur throughout the body, as indicated above, and may vary
by patient. General systemic signs may include fatigue, fever, joint and muscle pain, as
well as other specific issues noted above. Please study the figure in order to recall the
manifestations of lupus.
A common hallmark sign is a butterfly rash across the face, as well as overall sun
sensitivity of the skin.
BIOL205 – Lecture 2
Doktorinternet. (2013, May 15). Lupus [Photo]. Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:Lupusfoto.jpg
Diagnosis
Diagnosis of lupus is based on exclusion of other diseases that appear similar and as
well as specific diagnostic criteria as indicated in the table below. A score of 10 will
indicate a lupus diagnosis.
28
BIOL205 – Lecture 2
Author, A. (2020, September 17). Systemic Lupus Erythematosus | Disease Week. Arkana Laboratories.
https://www.arkanalabs.com/introduction-to-systemic-lupus-erythematosus-and-clinicaldiagnostic-criteria/
29
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Treatment
Treatment for lupus will vary based on organ system involvement. In addition,
protection from sunlight, smoking cessation, proper nutrition, exercise, and
immunizations are emphasized.
Subject 3: Immune Deficiency
The final type of immune disorders are immune deficiencies. In general, this means that
the immune system is not functioning properly, which can lead to the development of
infectious diseases and cancer. Immunodeficiencies may be either primary (meaning
that they originate with the organ system in question), or secondary (meaning that they
are due to a different pathologic process). Immunodeficiencies can lead to
opportunistic infections, which are infections that don’t typically occur in individuals
with a functional immune system.
Primary immunodeficiencies are rare, and usually genetic. They typically involve a
defect in a certain component of the immune system, such as T cells, B cells, NK cells, or
particular classes of antibodies. Manifestations include recurrent and/or severe or
persistent infections.
One example of a primary immunodeficiency is Severe Combined Immunodeficiency
(SCID). The most well known patient with this disorder is David Vetter, also known as
the boy in the bubble, whose life was documented via television and movies (The Story
of David Vetter | Immune Deficiency Foundation, n.d.). This condition results from a
genetic disorder leading to the absence of both B and T cells, meaning that there is little
to no protection from disease after maternal antibodies are gone. Recurrent infections
occur in the first months of life, and the disease is terminal unless a successful stem cell
transplant of healthy immune cells occurs.
Secondary immunodeficiencies are acquired, and there are a number of factors that
increase the risk of immune deficiency, including poor nutrition, stress, aging,
chemotherapy, and immunosuppressive treatments.
The most common cause of secondary immunodeficiency is Acquired Immune
Deficiency Syndrome (AIDS), which develops as a result of Human
Immunodeficiency Virus (HIV) infection. We’ll explore AIDS in more depth in this
lesson.
HIV/AIDS
Causative Agent
HIV is an enveloped RNA retrovirus, which means that they insert a DNA copy of their
genome into the host cell.
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(Sorenson et al. 2019, Figure 15.3)
It specifically infects cells of the immune system, in particular helper T cells, which are
CD4+ (they have a CD4+ marker on their cell surface). The process is outlined below.
While it’s not necessary to know each step in the process, it’s important to see key steps,
as they are places where drugs intervene to slow viral replication.
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(Sorenson et al. 2019, Figure 15.4)
Transmission
HIV is transmitted via blood and body fluids. In order for HIV to be transmitted, an
infected host must have sufficient viral particles in a body fluid and the fluid must be in
contact with body fluid of the uninfected individual. Sexual contact is the primary
mode of transmission worldwide, with penile-anal and penile-vaginal intercourse being
the most effective. HIV can also cross the placenta and be transmitted via breastmilk.
Manifestations
Manifestations will depend on the stage of infection.
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(Sorenson et al. 2019, Figure 15.5)
The graph is plotting two things: the CD4+ lymphocyte count (in blue), and the HIV
viral load (in red). In addition, please note that the Y-axis, showing time, is split with
weeks at first, and then years. We can see several different stages of the disease process.





At the initial infection, CD4+ lymphocyte levels are high, and obviously HIV
levels are low.
Following infection, the acute syndrome occurs 2-4 weeks later as HIV has an
initial replication burst. This stage lasts a couple of weeks, and is characterized
by body aches, fever, fatigue, headache, etc. These result from the body fighting
the viral infection. Because the body has not responded to infection yet, viral
titers are high, and individuals are highly contagious. Additionally, there is a
transient drop in CD4+ cells.
At some point, the body begins to mount an immune response, and antibodies to
HIV will appear in the blood. This is termed, “seroconversion.” Because most
diagnostic tests detect antibodies to HIV, individuals testing before this occurs
will falsely test negative. Once antibodies are made, the levels of HIV decrease
again, and CD4+ cells rise a bit.
Chronic infection occurs over a period of years, even with no treatment. During
this time, the individual is asymptomatic. However, HIV levels are rising, and
CD4+ cells are decreasing. Without treatment, this stage may last as long as 10
years.
As CD4+ cells decrease, symptomatic disease will occur in the form of HIV
related conditions, which are mainly opportunistic infections. More on that to
come.
BIOL205 – Lecture 2
(Sorenson et al. 2019, Figure 15.6)
HIVAIDS. (2017, December 29). Stages of HIV [Image]. HIVAIDS Awareness and Education.
https://www.hivaidsclinichyderabad.com/latest-update/stages-of-hiv-depend/604
The CDC uses case definitions to determine the Stage of HIV infection, and it is based
on CD4+ cell count and the presence or absence of AIDS-defining conditions.
Information on this is shown below.
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AIDS occurs when the CD4+ count goes below 200 cells/mm3
AIDS defining conditions are particular illnesses that occur more frequently in
those with HIV infection and are used as indicators that HIV infection and AIDS
may be present.
CDC. (n.d.-a). Case Definition HIV infection [Illustration]. Hiv.UW.Edu.
https://www.hiv.uw.edu/go/basic-primary-care/staging-initial-evaluation-monitoring/coreconcept/all
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CDC. (n.d.-b). Opportunistic Illnesses [Image]. HIV. UW.Edu. https://www.hiv.uw.edu/go/basicprimary-care/staging-initial-evaluation-monitoring/core-concept/all
Diagnosis
Diagnosis of HIV/AIDS occurs via blood testing for HIV antibodies, as well as CD4+
cell counts, and the presence of AIDS defining conditions.
Treatment
Treatment of HIV infection is via antiretroviral therapy (ART). Typically, this involves a
combination of at least three medications to slow viral replication. A combination of
drugs, termed highly active antiretroviral therapy (HAART) helps reduce viral
resistance to anti-viral medication.
Prevention
Prevention of HIV infection is also an option both for individuals at higher risk of
exposure, and health care providers who have had an exposure.
Please watch the following 2 minute, 26-second video by AMAZE Org. As you watch
the video, consider the following:
• What does PrEP stand for, and what does it do?
• What does PEP stand for and what does it do?
Click the following link to watch:
PrEP and PEP: HIV Prevention
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Org, A. (2021, July 22). PrEp and Pep: HIV Prevention [Video]. YouTube.

Video Takeaways
PrEP stand for pre-exposure prophylaxis, and it involves taking daily medication to
reduce the risk of infection with HIV in individuals at high risk. PEP stands for postexposure prophylaxis and it is a onetime treatment regimen for individuals who have
had an exposure, and it must be started within 72 hours.
Opportunistic Infections
Due to a weakened immune system, infection occurs with increased frequency or
severity. Here are some examples of opportunistic infections associated with AIDS.
Category
Bacterial
Fungal
Parasitic
Viral
Cancer-causing
Infectious agent
Salmonella sp.
Mycobacterium tuberculosis
Candida
Coccidioides
Pneumocystis jiroveci
Cryptosporidium
Toxoplasma gondii
Cytomegalovirus (CMV)
Herpes simplex virus (HSV)
Human papilloma virus (HPV)
Human herpes virus 8
none
Disease
Salmonella septicemia
Tuberculosis
Candidiasis (oral and vaginal)
Coccidioidomycosis
PCP pneumonia
Cryptosporidiosis (crypto)
Toxoplasmosis
Various types of infection
Oral or genital sores
Cervical cancer
Kaposi’s sarcoma
Lymphoma
A number of these infectious agents may be latent or silent and would not cause illness
in a healthy host, but when the immune system is deficient enough, infection occurs.
Examples of these include the microbes that cause tuberculosis and toxoplasmosis.
Furthermore, fungal infections are relatively rare in individuals with healthy immunity,
but much more common with AIDS.
Because the immune system halts cancer cells, there are certain cancers that occur more
frequently in AIDS patients. Kaposi’s sarcoma is the most common AIDS associated
malignancy. It causes vascular skin lesions, shown below.
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(Sorenson et al. 2019, Figure 15.7)
Lesson 3 Completed!
Thank you! You have completed this lesson. Please scroll down to complete a short,
ungraded Knowledge Check activity.
Check Your Knowledge 3
Drag and Drop Activity
Directions: Match the following concepts, stages, and responses by dragging the (Items
to Match) to the corresponding place within the diagram. You will have two attempts.
Click submit to check your answers.
BIOL205 – Lecture 2
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BIOL205 – Lecture 2
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Drag and Drop Activity
Directions: Match the following terms by dragging the (Items to Match) to the
corresponding placement within the graph. You will have two attempts. Click submit to
check your answers.
Lesson 4 – Genetic and Congenital Disorders
Introduction
In this final lesson, we will switch gears and discuss congenital and genetic disorders. A
congenital disorder is one that is present at birth; it may be genetic or it may be due to
environmental factors affecting the embryo or fetus. A genetic disorder is one that is
present in the genome or DNA – it is present at birth, but it may or may not be evident at
birth. Genetic disorders can be caused by changes in individual genes or by changes in
whole chromosomes.
Subject 1: Genetics Refresher
Let’s start with a brief refresher on basic genetics. Genetic information is carried on
molecules of DNA, which is a double helix with paired nucleotide bases as the “rungs.”
BIOL205 – Lecture 2
(Sorenson et al. 2019, Figure 2.3)
(Sorenson et al. 2019, Figure 2.4)
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Please watch the following 3 minute, 56-second video By: Rachel Taylor to review
information on DNA, genes, and chromosomes. As you watch the video, consider the
following:
• What is DNA?
• How many chromosomes do humans have?
• What is a gene? Do we know the location of particular genes?
Click the following link to watch:
DNA, Chromosomes & Genes
By: Rachel Taylor. (2021, February 19). DNA, Chromosomes & Genes [Video]. YouTube.

Video Takeaways
DNA is found in every cell in your body, and it contains the instructions that code for
all characteristics of a species. Humans have 46 chromosomes (23 pairs, one each from
mom and one from dad). A gene is a specific segment of DNA that codes for a
particular protein, which gives us our traits. Genes are located in specific places within
particular chromosomes, and these have been mapped.
An image of a person’s chromosomes arranged in pairs by size and numbers is called a
karyotype. The first 23 pairs are called autosomes, and the 23rd pair contains the sex
chromosomes. Females will have 2 X chromosomes and males will have an X and a Y.
This means that females have two copies of each of the genes on chromosome X,
whereas males just have one. This will be important later. Only males have genes found
on the Y chromosome, and these generally code for proteins related to becoming male.
Below is a karyotype for a male human.
National Human Genome Research Institute. (n.d.). Human male karyotype [Image]. Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:Human_male_karyotype.gif
Below is a pictorial representation of some of the genes for diseases found on
chromosome 5.
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Human genome project. (n.d.). Human genome poster [Image]. Human Genome Project.
https://web.ornl.gov/sci/techresources/Human_Genome/posters/chromosome/chromo05.sht
ml
Because there are two copies of each chromosome, each person has two copies of each
gene, and each copy is called an allele. The particular location of a given gene on a
chromosome is called its locus. Many genes have only one normal/healthy version of a
given gene, while others have multiple possible normal alleles.
Through the processes of transcription and translation, depicted below, genes code for
proteins, and proteins are what determine our traits.
TRANSCRIPTION – making a copy of the DNA for a gene onto mRNA
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(Sorenson et al. 2019, Figure 2.10)
TRANSLATION – turning the mRNA into a protein
(Sorenson et al. 2019, Figure 2.13)
When there is an error in the DNA sequence of a gene, that’s called a mutation. Many
mutations that occur are point mutations of a single base, within a single gene. As we
have seen, these can lead to cancer. When they are passed down to offspring, they can
cause genetic diseases. In addition, changes to a chromosome may occur which impact
many genes.
Categories of Genetic Disorders
In terms of genetic disorders, we can consider three categories.
1. Single gene disorders: These occur when there are changes to a single gene, thus
leading to changes in a single protein. We’ll consider various types of inheritance
BIOL205 – Lecture 2
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patterns related to single gene disorders.
2. Chromosomal disorders: These occur when there is an abnormality of
chromosome number or function. Sometimes chromosomes don’t separate
properly during cell division, and chromosomal disorders can occur. We will see
three examples of these below.
3. Multifactorial disorders: Most diseases occur because of interactions between
multiple genes and the environment. When we think of conditions like
hypertension or cardiovascular disease, there are multiple genes involved, but
also environmental factors, such as diet and exercise that play a role. This will be
the topic of many diseases of organ systems in later lectures.
Subject 2: Single Gene Disorders
Single gene disorders are caused by a defect in only one gene, leading to a malfunction
of a particular protein. Signs of these may or may not be present at birth.
These follow Mendelian genetics and can be tracked using Punnett squares, and they
may be inherited in a dominant or recessive fashion.
Let’s take a look back at history, with Gregor Mendel and his pea plants to review
single gene inheritance and Punnett squares. Pay close attention to and get a firm grasp
of these terms: homozygous, heterozygous, dominant, recessive, phenotype and
genotype. Please watch the following 3 minutes, 6-second video by TED-Ed.
Click the following link to watch:
How Mendel’s pea plants helped us understand genetics
T.-E. [TedEd]. (2013, March 12). How Mendel’s pea plants helped us understand genetics – Hortensia Jiménez
Díaz [Video]. YouTube. https://www.youtube.com/watch?v=Mehz7tCxjSE&feature=youtu.be
If a person has two copies of the same allele for a gene, this is termed homozygous. If
there are two different alleles for a gene, this is heterozygous. The term “expression” of
a gene refers to showing the trait. Dominant genes are expressed even if only one copy
is present. Recessive genes are only expressed if not dominant genes are present.
Alleles are represented by letters, with capital letters indicating a dominant trait, and
lowercase letters representing a recessive trait. The genotype is the combination of
alleles that are inherited, whereas the phenotype is what trait is shown.
With these concepts in mind, let’s jump into various inheritance patterns. We’ll consider
three different inheritance patterns and look at examples of diseases which fall in each
category. When we are learning about genetic disorders, it is very important to
remember which category each falls into – that’s part of knowing about a disease. It will
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impact how you interpret the Punnett squares, and in a clinical setting, how you
counsel patients. In the examples below, the “bad” or mutated allele will be presented
in red, and the normal or healthy allele will be in black to help us keep track.
Autosomal Recessive Disorders
Autosomal means that the gene of interest is on a non-sex chromosome, thus males and
females are equally affected. Recessive means that the defective gene is a recessive
allele, so the disease only manifests when an individual is homozygous for the defective
allele (aa).




An individual must have TWO bad copies of the gene in order to have the
disease – one inherited from each parent.
Individuals may inherit one bad copy of the gene (heterozygous — Aa). They are
unaffected by the disorder but are termed a “carrier” because they carry a copy
of the gene.
As we’ll see, the parents are usually unaffected. Both must have at least one bad
copy of the gene (carriers).
Because the gene can be present but not expressed, the disease does not appear
in every generation.
Let’s look at an example of inheritance of an autosomal recessive disorder using a
Punnett square.
A
a
A
a
AA
Aa
Aa
aa
Here are the results:
25% AA Unaffected
50% Aa Unaffected/Carrier
25% aa Have the disease
We can see that if both parents are carriers, there’s a 25% chance of offspring inheriting
the disorder and that both parents must carry a bad copy of the gene. In a medical
setting, it is possible to conduct genetic screening for carriers for many genetic diseases.
Carrier frequencies for recessive disorders vary among different ethnic groups.
Let’s consider a few examples of autosomal recessive disorders:
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Cystic fibrosis (CF) is an autosomal recessive disorder that primarily affects the
respiratory system. The mutation is in a chloride channel gene, and the result is
sticky, thick mucous in various tracts in the body. In the respiratory tract, this
mucous increases the risk of infection and blocks airways. CF also reduces the
secretion of digestive enzymes from the pancreas, leading to problems with
digestion. CF is more common in individuals of European descent.

Sickle cell anemia (SCA) is an autosomal recessive disorder that causes red
blood cells to become deformed in low oxygen. The sickle shaped cells can lodge
in capillaries causing infarcts, pain, and necrosis. In addition, the RBCs rupture
more easily leading to anemia. SCA is more common in individuals of African
descent.

Tay Sachs disease is a lysosomal storage disorder that leads to progressive
neurological and physical decline leading to death by age 4-5. Genes for this
disorder are more common in Jews of Eastern European descent.
One way to look at family history of a genetic disorder is by constructing a pedigree,
which is basically a family tree. In a pedigree, generations go from the top down. Males
are indicated by squares, whereas females are represented by circles. Reproducing pairs
are linked by a horizonal line, and offspring branch from the pair. Individuals with the
trait in question have a shaded in shape, and those who do not have an unshaded
shape. If carriers are known, they are indicated by a split symbol or a dot in the middle.
We can examine family history of a genetic disease and infer information about the
inheritance characteristics with a pedigree.
Kahn Academy. (n.d.). Pedigrees review. Retrieved April 29, 2022, from
https://www.khanacademy.org/science/ap-biology/heredity/non-mendelian-genetics/a/hspedigrees-review
BIOL205 – Lecture 2
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Here’s a pedigree for an autosomal recessive trait. Note that the disease does not occur
in every generation. In most cases, the genotype would not be known, but it is indicated
in this diagram.
Storyminusthes. (2021, November 14). Autosomal recessive pedigree [Image]. Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:Example_autosomal_recessive_pedigree.png
Autosomal recessive traits occur more frequently in close intermarriages, because more
family members are likely to be carriers. This is why you can’t marry your cousin!
Watch the following 3 minute, 46 second video to learn more.
Click here to learn more:
Is marrying your cousin actually dangerous?
Is marrying your cousin actually dangerous? (2018, August 4). Business Insider.
https://www.businessinsider.com/science-marry-your-cousin-safe-genetics-20187?international=true&r=US&IR=T
Autosomal Dominant Disorders
Dominant means that the defective gene is a dominant allele, so the disease manifests
even when there is only one copy of the gene.
• Defective gene is expressed
• AA: has the disorder
• Aa: has the disorder
• aa: unaffected



Only one bad copy of the gene is required to have the disorder.
Males and females are equally affected.
There is a 50% chance of being affected if one parent has the disorder.
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49
A person either has the disorder or does not have the disorder: there are no
carriers.
Because if the gene is present, it will be expressed, so it will appear in every
generation.
Let’s look at an example of inheritance of an autosomal dominant disorder using a
Punnett square. It is unlikely that both parents would have the disorders, so we look at
one parent with the disorder.
a
a
A
a
Aa
aa
Aa
aa
Here are the results:
50% Aa Have the disorder
50% aa Unaffected
We can see that if one parent has the disorder, there is a 50% chance that offspring have
the disorder. While some are inherited, some autosomal dominant disorders occur from
a new spontaneous mutation. In addition, many autosomal dominant disorders have an
adult onset, so the individual may have reproduced (and potentially passed on genes)
before they know they have the disorder.
Let’s consider a few examples of autosomal dominant disorders:
1. Marfan syndrome is an autosomal dominant disorder that results from a
mutation in the fibrillin I gene, a connective tissue protein. The production of a
defective connective tissue protein causes damage to many organs. Individuals
with this disorder tend to have a tall, thin body, and hyperextensible joints and
tendons. Heart valves and blood vessels may be weak, and the lens of the eye
may be displaced, causing myopia. Athletes are screened for Marfan syndrome,
because strenuous activity may cause an aortic dissection, which can be fatal.
Treatment involves decreased activity levels, and ongoing assessment of eye and
cardiovascular status.
2. Huntington disease is an autosomal dominant disorder that has an adult onset
neurodegeneration and chorea (involuntary jerking or twitching).
Here’s a pedigree for an autosomal dominant trait. Note that the disease does occur in
every generation and it occurs equally in men and women. In most cases, the genotype
would not be known, but it is indicated in this diagram.
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Storyminusthes. (n.d.). Autosomal Dominant pedigree [Image]. Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:Example_autosomal_dominant_pedigree_01.png
X-linked (sex linked) Inheritance
X-linked (or sex linked) means that the defective gene is a found on the X chromosome.
While there are Y-linked disorders they are not common. Typically X linked disorders
are recessive, and the examples provided are recessive. Because females have 2 X
chromosomes, if there is a defective recessive allele, the effect of this may be masked by
the healthy allele on the other chromosome. However, for males, there is only one X
chromosome, so whatever allele is present is what is expressed.
• Because males have only
one copy of the X, (XY) they
only need one bad copy of
the gene.
• Males:
• XY: unaffected
• XY: affected






• Because females have two
copies of the X, (XX) they
may be a carrier or affected
if they have two bad copies
• Females:
• XX: unaffected
• XX: unaffected carrier
• XX: has the disorder
The defective X in males is unmasked
and expressed.
Males either have the disorder or do not: there are no MALE carriers.
Because of this, X linked disorder appear more frequently in males.
Affected males pass the defective gene to their daughter.
Females are usually carriers, with one bad copy of the gene.
Females may get an X-linked disorder if they inherit a bad copy of the gene from
both parents.
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Let’s look at an example of inheritance of a sex-linked disorder using a Punnett square.
X
Y
X
X
XX
XX
XY
XY
Here are the results:
25% XX Unaffected female
25% XX Carrier female
25% XY Unaffected male
25% XY Affected male
We can see that the results depend on the sex off the offspring.
Let’s consider a few examples of an autosomal dominant disorders:
Red-green colorblindness is a trait that means that a person has the inability to
distinguish between red and green colors.
Hemophilia A is a clotting disorder where the affected individual is lacking a particular
clotting factor, and thus will have a tendency to bleed too much.
Here’s a pedigree for a sex-linked disorder. Note that the disease skips generations
(recessive trait) and that women tend to be carriers, while males are never carriers.
Hydra2114. (2018, June 1). Sex linked recessive pedigree [Image]. Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:Sex-Linked_Recessive_Pedigree.svg
BIOL205 – Lecture 2
52
Subject 3: Chromosomal Disorders
Chromosomal disorders result when there is an abnormality in the number or structure
of the chromosomes. Because chromosomes contain many genes, Punnett squares
cannot be used in these disorders. Rather, they may be diagnosed using karyotypes.
Usually, chromosomal disorders occur when there is an error in meiosis, whereby the
wrong number of chromosomes separate into a given cell. This is termed chromosome
nondisjunction. This process occurs more often in older mothers. Most occurrences of
nondisjunction are not compatible with life and result in an early miscarriage, but some
may result in a live birth: we’ll discuss three examples of that here.
Down Syndrome/Trisomy 21
Down syndrome is a condition resulting from having 3 copies of the 21st chromosome.
U.S. Department of Energy Human Genome Program. (2006, October 5). Down syndrome karyotype
[Image]. Wikimedia Commons. https://commons.wikimedia.org/wiki/File:21_trisomy__Down_syndrome.png
Down syndrome is associated with certain characteristic facial features (including short
neck, upward slating eyes, single deep palmar crease, flattened facial profile and nose),
variable degrees of intellectual disability, and some conditions that occur more
frequently (congenital heart abnormalities, acute lymphoblastic leukemia, hearing and
vision problems, and Autism spectrum disorder).
Turner Syndrome
Turner syndrome occurs when there is only a single copy of the X chromosome.
BIOL205 – Lecture 2
53
Turner Syndrome vs. Klinefelter Syndrome. (2020, May 11). Diffzi. https://diffzi.com/turner-syndrome-vsklinefelter-syndrome/
Klinefelter Syndrome
Klinefelter syndrome occurs when there are multiple copies of the X chromosome and
the presence of a Y chromosome.
Turner Syndrome vs. Klinefelter Syndrome. (2020, May 11). Diffzi. https://diffzi.com/turner-syndrome-vsklinefelter-syndrome/
Subject 4: Developmental Disorders
Some disorders may be present at birth, or shortly after birth, but they are not caused
by genetic or chromosomal abnormalities. These typically occur due to some failure in
BIOL205 – Lecture 2
54
development during the embryonic stage or in the first two months of pregnancy.
Because they are not genetic, they cannot be transmitted to offspring. Sometimes these
errors occur spontaneously, and sometimes they are the result of exposure to
teratogens.
A teratogen is an agent or factor that causes malformation of an embryo. These agents
include certain drugs, environmental agents, infectious diseases, nutritional
deficiencies, etc. The image below shows the times when embryos and fetuses are most
susceptible to teratogenic agents, and what organ systems are most vulnerable at
various times.
Santrock. (2009). Teratogens [Image]. Expecting Parents. https://expectingparent.weebly.com/fertility-pregnancy.html
All medications are classified by the FDA to indicate the potential risk for a fetus.
BIOL205 – Lecture 2
55
FDA. (n.d.). FDA pregnancy categories [Image]. USPharmacist.
https://www.uspharmacist.com/article/new-changes-in-pregnancy-and-lactation-labeling
Lesson 4 Completed!
Thank you! You have completed this lesson. Please scroll down to complete a short,
ungraded Knowledge Check activity.
Check Your Knowledge 4
Drag and Drop Activity
Place the disorder in the proper category.
Single gene:
Single gene:
autosomal
autosomal
recessive
dominant
Cystic fibrosis
Marfan syndrome
Sickle cell anemia
Single gene: X
linked
Chromosomal
Red/green
colorblindness
Down syndrome
Huntington disease
Turner syndrome
Hemophilia A
Tay Sachs disease
Klinefelter
syndrome
Lecture Recap
In this lecture, we examined the normal function of the immune system, with a specific
highlight on the inflammatory process. Next, we covered the types of disorders that
occur as a result of immune system dysfunction. Finally, we examined genetic and
congenital disorders by sorting them into a single gene, chromosomal and
developmental disorders.
For the next lecture, we’ll look at fluid and electrolyte balance in the body and
understand how the body establishes homeostasis. Then we’ll delve into acid/base
imbalances and arterial blood gas analysis.
BIOL205 – Lecture 2
56
References
AMBOSS: Medical Knowledge Distilled. (2019, January 29). Immune Complex-Mediated
Hypersensitivity: Type III Hypersensitivity Reaction [Video]. YouTube.

AMBOSS: Medical Knowledge Distilled. (2020, December 17). Innate and Adaptive
Immunity: Types of Immune Responses (Short version) [Video]. YouTube.

Author, A. (2020, September 17). Systemic Lupus Erythematosus | Disease Week. Arkana
Laboratories. https://www.arkanalabs.com/introduction-to-systemic-lupuserythematosus-and-clinical-diagnostic-criteria/
By: Rachel Taylor. (2021, February 19). DNA, Chromosomes & Genes [Video]. YouTube.

CDC. (n.d.-a). Case Definition HIV infection [Illustration]. Hiv.UW.Edu.
https://www.hiv.uw.edu/go/basic-primary-care/staging-initial-evaluationmonitoring/core-concept/all
CDC. (n.d.-b). Opportunistic Illnesses [Image]. HIV. UW.Edu.
https://www.hiv.uw.edu/go/basic-primary-care/staging-initial-evaluationmonitoring/core-concept/all
CDC. (n.d.-c). TB skin test [Image]. CDC.
https://www.cdc.gov/tb/webcourses/course/chapter3/3_testing_for_tb_disea
se_and_ltbi_3_mantoux_tuberculin_skin_test_reading_the_tst_induration.html
BIOL205 – Lecture 2
57
Classes of Antibodies. (n.d.). [Image]. BC Campus.

23.3. Antibodies


Connexions. (2013, September 6). Primary and Secondary Immune response [Image].
Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:2223_Primary_and_Secondary_Anti
body_Respons_new.jpg
Criticalbench. (2014, January 13). Chronic Inflammation: The Root Cause of a Multitude of
Diseases [Video]. YouTube. https://www.youtube.com/watch?v=GTu7KUXOrU&feature=youtu.be
Doktorinternet. (2013, May 15). Lupus [Photo]. Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:Lupusfoto.jpg
FDA. (n.d.). FDA pregnancy categories [Image]. USPharmacist.
https://www.uspharmacist.com/article/new-changes-in-pregnancy-andlactation-labeling
HAL Allergy Group. (2015, February 10). How to diagnose an allergy? [Video]. YouTube.


HIVAIDS. (2017, December 29). Stages of HIV [Image]. HIVAIDS Awareness and
Education. https://www.hivaidsclinichyderabad.com/latest-update/stages-ofhiv-depend/604
Human genome project. (n.d.). Human genome poster [Image]. Human Genome Project.
https://web.ornl.gov/sci/techresources/Human_Genome/posters/chromosom
e/chromo05.shtml
BIOL205 – Lecture 2
58
Hydra2114. (2018, June 1). Sex linked recessive pedigree [Image]. Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:Sex-Linked_Recessive_Pedigree.svg
Is marrying your cousin actually dangerous? (2018, August 4). Business Insider.
https://www.businessinsider.com/science-marry-your-cousin-safe-genetics2018-7?international=true&r=US&IR=T
Kahn Academy. (n.d.). Pedigrees review. Retrieved April 29, 2022, from
https://www.khanacademy.org/science/ap-biology/heredity/non-mendeliangenetics/a/hs-pedigrees-review
Lippy, A. (2016, August 23). Acute Inflammation- Educational 3D Animation [Video].
YouTube.

National Human Genome Research Institute. (n.d.). Human male karyotype [Image].
Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:Human_male_karyotype.gif
NIAID. (2016, November 2). Natural Killer cells [Illustration]. National Institute of
Allergy and Infectious Disease.
https://commons.wikimedia.org/wiki/File:Natural_Killer_Cell_(30439199790).j
pg
OpenStax. (n.d.). Hypersensitivity [Image]. Wikimedia Commons.
https://en.wikipedia.org/wiki/Hypersensitivity
Org, A. (2021, July 22). PrEp and Pep: HIV Prevention [Video]. YouTube.

BIOL205 – Lecture 2
59
Santrock. (2009). Teratogens [Image]. Expecting Parents.
https://expectingparent.weebly.com/fertility–pregnancy.html
Sorenson, M., Quinn, L., & Klein, D. (2019). Pathophysiology. Pearson Education.
The Story of David Vetter | Immune Deficiency Foundation. (n.d.). Immune Deficiency
Foundation. Retrieved April 28, 2022, from https://primaryimmune.org/storydavid-vetter
Storyminusthes. (n.d.). Autosomal Dominant pedigree [Image]. Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:Example_autosomal_dominant_ped
igree_01.png
Storyminusthes. (2021, November 14). Autosomal recessive pedigree [Image]. Wikimedia
Commons.
https://commons.wikimedia.org/wiki/File:Example_autosomal_recessive_pedi
gree.png
T.-E. [TedEd]. (2013, March 12). How Mendel’s pea plants helped us understand genetics Hortensia Jiménez Díaz [Video]. YouTube.

Tokyogirl79. (2016, August 23). Epi-pen [Image]. Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:Epi-Pen_2016.jpg
Turner Syndrome vs. Klinefelter Syndrome. (2020, May 11). Diffzi.

Turner Syndrome vs Klinefelter Syndrome


BIOL205 – Lecture 2
60
U.S. Department of Energy Human Genome Program. (2006, October 5). Down syndrome
karyotype [Image]. Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:21_trisomy_-_Down_syndrome.png
Yahoo Life. (2018, August 10). This is what happens when you have an autoimmune disease
[Video]. YouTube.



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