D115 Advanced Pathophysiology
Comprehensive Answer Guide & Study Reference
OA Exam Prep — Units 2 through 7
Foundations of Pathophysiology — Genes, Lifestyle & Immunity
Module 1: Genetic Influence on Patient Outcomes
Q: What are genes composed of and where are they located?
A: Genes are composed of DNA (deoxyribonucleic acid) — segments of DNA that encode proteins. They are located
on chromosomes inside the nucleus of cells.
Q: What are the four nitrogenous bases that make up DNA?
A: Adenine (A), Thymine (T), Guanine (G), and Cytosine (C). A pairs with T; G pairs with C. In RNA, Uracil (U)
replaces Thymine.
⭐ HIGH YIELD: A-T and G-C base pairing is a common exam question. Remember: in RNA, T → U.
Q: How are new strands of DNA formed?
A: Through DNA replication: the double helix unwinds, and each strand serves as a template. DNA polymerase adds
complementary nucleotides (A→T, G→C) forming two identical daughter strands.
Q: How is transcription regulated?
A: Transcription (DNA→mRNA) is regulated by promoter regions, transcription factors, enhancers/silencers, and
epigenetic modifications (methylation, histone modification) that control whether a gene is expressed or silenced.
Q: How many pairs of chromosomes do humans have?
A: Humans have 46 chromosomes total — 23 pairs. 22 pairs are autosomes; 1 pair are sex chromosomes (XX =
female, XY = male).
Q: Most common chromosome abnormalities?
A: Trisomy 21 (Down syndrome), Monosomy X (Turner syndrome — 45,X), Trisomy XXY (Klinefelter syndrome —
47,XXY), deletions, duplications, and translocations.
Q: How is gender determined genetically?
A: The SRY gene on the Y chromosome triggers male development. XX = female; XY = male. Individuals with no Y
chromosome develop as female by default.
Q: What are multifactorial diseases? Name examples.
A: Diseases caused by the interaction of multiple genes AND environmental factors. Examples: type 2 diabetes,
hypertension, coronary artery disease, cleft palate, neural tube defects, schizophrenia.
Q: How do monozygotic and dizygotic twins differ genetically?
A: Monozygotic (identical) twins share 100% of DNA — from one fertilized egg. Dizygotic (fraternal) twins share ~50%
of DNA — from two separate eggs fertilized by two sperm.
Q: Which chromosome is affected in Down syndrome? Clinical features?
A: Trisomy 21 (three copies of chromosome 21). Features: intellectual disability, flat facial profile, upslanting palpebral
fissures, single palmar crease, low-set ears, hypotonia. Risks: congenital heart defects (AV canal), early-onset
Alzheimer's, hypothyroidism, leukemia.
1..
, lOMoARcPSD|64492663
D115 Advanced Pathophysiology — OA Answer Guide
⭐ HIGH YIELD: Down syndrome = Trisomy 21. Most common chromosome abnormality. Associated with
advanced maternal age.
Q: Turner syndrome — chromosomes, features, treatment?
A: Monosomy X (45,X). Features: short stature, webbed neck, shield chest, primary amenorrhea, infertility,
coarctation of aorta, bicuspid aortic valve. Treatment: growth hormone, estrogen replacement therapy.
Q: Klinefelter syndrome — chromosomes, features?
A: 47,XXY. Features: tall stature, small testes, gynecomastia, infertility (azoospermia), learning difficulties.
Often not diagnosed until puberty or adulthood.
Q: Types of genetic testing?
A: Carrier screening (identifies carriers of recessive disorders), prenatal testing (amniocentesis, CVS),
newborn screening, diagnostic testing, predictive/presymptomatic testing (e.g., BRCA gene testing).
Module 2: Pathological Defense Mechanisms & Immunity
Q: What are the 3 layers of human defense?
A: 1st line: Physical/mechanical barriers (skin, mucous membranes, cilia, stomach acid). 2nd line: Innate
immunity (inflammation, phagocytes, fever, complement). 3rd line: Adaptive immunity (T cells, B cells,
antibodies — specific and memory-forming).
⭐ HIGH YIELD: Know the sequence: Barrier → Innate (non-specific, fast) → Adaptive (specific, slow but
memory).
Q: How do acute and chronic inflammation differ?
A: Acute inflammation: rapid onset (minutes-hours), dominated by neutrophils, vascular changes (redness,
heat, swelling, pain, loss of function), usually resolves. Chronic inflammation: weeks-months, dominated by
macrophages and lymphocytes, may cause tissue destruction and fibrosis (e.g., rheumatoid arthritis, TB).
Q: What are the phases of wound healing?
A: 1) Hemostasis (0–24 hrs): vasoconstriction, platelet plug, clot formation. 2) Inflammation (1–3 days):
neutrophils then macrophages clean debris. 3) Proliferation (3–21 days): fibroblasts lay collagen,
angiogenesis, epithelialization. 4) Remodeling (21 days–2 years): collagen reorganizes, scar matures.
Q: Describe the process of adaptive immunity.
A: Antigen is presented by APCs (antigen-presenting cells) via MHC molecules. Naïve T cells are activated
and differentiate into helper T cells (CD4+) and cytotoxic T cells (CD8+). B cells are activated (with T cell
help) → differentiate into plasma cells that produce antibodies. Memory cells are formed for faster future
responses.
Q: Identify the 4 types of hypersensitivity reactions.
A: Type I (Immediate/Anaphylactic): IgE mediated, mast cells/basophils, occurs within minutes. Examples:
anaphylaxis, allergic asthma, hay fever. Type II (Cytotoxic): IgG/IgM against cell surface antigens. Examples:
hemolytic transfusion reactions, Graves disease. Type III (Immune complex): IgG/IgM complexes deposit in
tissues. Examples: SLE, serum sickness, glomerulonephritis. Type IV (Delayed/Cell-mediated): T cell
mediated, 48–72 hrs. Examples: contact dermatitis, TB skin test, transplant rejection.
⭐ HIGH YIELD: Type I = IgE. Type IV = T cells (no antibodies). Memorize: 1=IgE/mast cells; 2=cytotoxic;
3=immune complex; 4=T-cell delayed.
Q: What causes autoimmune diseases?
A: Molecular mimicry (pathogen antigens resemble self-antigens), failure of clonal deletion, loss of regulatory
T cell function, exposure of hidden antigens, genetic predisposition (HLA alleles).
Q: What are HLA alleles and disease associations?
A: HLA = Human Leukocyte Antigen (MHC). Key associations: HLA-DR3/DR4 → Type 1 Diabetes; HLA-B27
→ Ankylosing Spondylitis; HLA-DR4 → Rheumatoid Arthritis; HLA-DR3 → SLE; HLA-DR3 → Graves disease.
Page 1
Comprehensive Answer Guide & Study Reference
OA Exam Prep — Units 2 through 7
Foundations of Pathophysiology — Genes, Lifestyle & Immunity
Module 1: Genetic Influence on Patient Outcomes
Q: What are genes composed of and where are they located?
A: Genes are composed of DNA (deoxyribonucleic acid) — segments of DNA that encode proteins. They are located
on chromosomes inside the nucleus of cells.
Q: What are the four nitrogenous bases that make up DNA?
A: Adenine (A), Thymine (T), Guanine (G), and Cytosine (C). A pairs with T; G pairs with C. In RNA, Uracil (U)
replaces Thymine.
⭐ HIGH YIELD: A-T and G-C base pairing is a common exam question. Remember: in RNA, T → U.
Q: How are new strands of DNA formed?
A: Through DNA replication: the double helix unwinds, and each strand serves as a template. DNA polymerase adds
complementary nucleotides (A→T, G→C) forming two identical daughter strands.
Q: How is transcription regulated?
A: Transcription (DNA→mRNA) is regulated by promoter regions, transcription factors, enhancers/silencers, and
epigenetic modifications (methylation, histone modification) that control whether a gene is expressed or silenced.
Q: How many pairs of chromosomes do humans have?
A: Humans have 46 chromosomes total — 23 pairs. 22 pairs are autosomes; 1 pair are sex chromosomes (XX =
female, XY = male).
Q: Most common chromosome abnormalities?
A: Trisomy 21 (Down syndrome), Monosomy X (Turner syndrome — 45,X), Trisomy XXY (Klinefelter syndrome —
47,XXY), deletions, duplications, and translocations.
Q: How is gender determined genetically?
A: The SRY gene on the Y chromosome triggers male development. XX = female; XY = male. Individuals with no Y
chromosome develop as female by default.
Q: What are multifactorial diseases? Name examples.
A: Diseases caused by the interaction of multiple genes AND environmental factors. Examples: type 2 diabetes,
hypertension, coronary artery disease, cleft palate, neural tube defects, schizophrenia.
Q: How do monozygotic and dizygotic twins differ genetically?
A: Monozygotic (identical) twins share 100% of DNA — from one fertilized egg. Dizygotic (fraternal) twins share ~50%
of DNA — from two separate eggs fertilized by two sperm.
Q: Which chromosome is affected in Down syndrome? Clinical features?
A: Trisomy 21 (three copies of chromosome 21). Features: intellectual disability, flat facial profile, upslanting palpebral
fissures, single palmar crease, low-set ears, hypotonia. Risks: congenital heart defects (AV canal), early-onset
Alzheimer's, hypothyroidism, leukemia.
1..
, lOMoARcPSD|64492663
D115 Advanced Pathophysiology — OA Answer Guide
⭐ HIGH YIELD: Down syndrome = Trisomy 21. Most common chromosome abnormality. Associated with
advanced maternal age.
Q: Turner syndrome — chromosomes, features, treatment?
A: Monosomy X (45,X). Features: short stature, webbed neck, shield chest, primary amenorrhea, infertility,
coarctation of aorta, bicuspid aortic valve. Treatment: growth hormone, estrogen replacement therapy.
Q: Klinefelter syndrome — chromosomes, features?
A: 47,XXY. Features: tall stature, small testes, gynecomastia, infertility (azoospermia), learning difficulties.
Often not diagnosed until puberty or adulthood.
Q: Types of genetic testing?
A: Carrier screening (identifies carriers of recessive disorders), prenatal testing (amniocentesis, CVS),
newborn screening, diagnostic testing, predictive/presymptomatic testing (e.g., BRCA gene testing).
Module 2: Pathological Defense Mechanisms & Immunity
Q: What are the 3 layers of human defense?
A: 1st line: Physical/mechanical barriers (skin, mucous membranes, cilia, stomach acid). 2nd line: Innate
immunity (inflammation, phagocytes, fever, complement). 3rd line: Adaptive immunity (T cells, B cells,
antibodies — specific and memory-forming).
⭐ HIGH YIELD: Know the sequence: Barrier → Innate (non-specific, fast) → Adaptive (specific, slow but
memory).
Q: How do acute and chronic inflammation differ?
A: Acute inflammation: rapid onset (minutes-hours), dominated by neutrophils, vascular changes (redness,
heat, swelling, pain, loss of function), usually resolves. Chronic inflammation: weeks-months, dominated by
macrophages and lymphocytes, may cause tissue destruction and fibrosis (e.g., rheumatoid arthritis, TB).
Q: What are the phases of wound healing?
A: 1) Hemostasis (0–24 hrs): vasoconstriction, platelet plug, clot formation. 2) Inflammation (1–3 days):
neutrophils then macrophages clean debris. 3) Proliferation (3–21 days): fibroblasts lay collagen,
angiogenesis, epithelialization. 4) Remodeling (21 days–2 years): collagen reorganizes, scar matures.
Q: Describe the process of adaptive immunity.
A: Antigen is presented by APCs (antigen-presenting cells) via MHC molecules. Naïve T cells are activated
and differentiate into helper T cells (CD4+) and cytotoxic T cells (CD8+). B cells are activated (with T cell
help) → differentiate into plasma cells that produce antibodies. Memory cells are formed for faster future
responses.
Q: Identify the 4 types of hypersensitivity reactions.
A: Type I (Immediate/Anaphylactic): IgE mediated, mast cells/basophils, occurs within minutes. Examples:
anaphylaxis, allergic asthma, hay fever. Type II (Cytotoxic): IgG/IgM against cell surface antigens. Examples:
hemolytic transfusion reactions, Graves disease. Type III (Immune complex): IgG/IgM complexes deposit in
tissues. Examples: SLE, serum sickness, glomerulonephritis. Type IV (Delayed/Cell-mediated): T cell
mediated, 48–72 hrs. Examples: contact dermatitis, TB skin test, transplant rejection.
⭐ HIGH YIELD: Type I = IgE. Type IV = T cells (no antibodies). Memorize: 1=IgE/mast cells; 2=cytotoxic;
3=immune complex; 4=T-cell delayed.
Q: What causes autoimmune diseases?
A: Molecular mimicry (pathogen antigens resemble self-antigens), failure of clonal deletion, loss of regulatory
T cell function, exposure of hidden antigens, genetic predisposition (HLA alleles).
Q: What are HLA alleles and disease associations?
A: HLA = Human Leukocyte Antigen (MHC). Key associations: HLA-DR3/DR4 → Type 1 Diabetes; HLA-B27
→ Ankylosing Spondylitis; HLA-DR4 → Rheumatoid Arthritis; HLA-DR3 → SLE; HLA-DR3 → Graves disease.
Page 1
