Lecture 5 Human Genetics 2

Question 1

Tay-Sachs Disease (TSD)

Answer 1

• A fatal, autosomal recessive neurodegenerative disease of infancy and early childhood 染色体隐性遗传性神经退行性疾病
• People carry the disease but may not be affected. Both parents need to carry the gene for it to be expressed in offspring.

Question 2

Tay-Sachs Disease (TSD) - Cause

Answer 2

Mutation in HEXA gene (chromosome 15q23-q24)

Question 3

Tay-Sachs Disease (TSD) - Key Symptom

Answer 3

Cherry-red spot in eyes, fatal neurodegeneration in infancy

• As the disease progresses, development slows and muscles begin to weaken. Over time, this leads to seizures, vision and hearing loss, paralysis, and other major issues.

Children with this form of Tay-Sachs disease typically live only a few years.

Question 4

Tay-Sachs Disease (TSD) - High-Risk Populations

Answer 4

Ashkenazi Jews (1:25 carriers), Cajuns, French Canadians

Question 5

Huntington’s Disease (HD) - Inheritance Pattern

Answer 5

Autosomal dominant progressive neurodegenerative disorder

Question 6

Huntington’s Disease (HD) - Genetic Cause

Answer 6

• ≥ 40 repeats of CAG (cytosine, adenine, guanine) trinucleotide in HTT gene (4p16.3)

Question 7

Huntington’s Disease (HD) - Key Symptoms

Answer 7

Chorea 舞蹈症 (involuntary movements), cognitive decline, onset ~40 years

Question 8

Huntington’s Disease (HD) - Juvenile Form

Answer 8

> 55 CAG repeats (Westphal variant), onset before age 20

Question 9

Fragile-X Syndrome (FXS) - Inheritance Pattern

Answer 9

X-linked

Question 10

Fragile-X Syndrome (FXS) - Cause

Answer 10

CGG repeat expansion in FMR1 gene (Xq27.3), silencing FMR1 protein

Question 11

Fragile-X Syndrome (FXS) - Key Features

Answer 11

Intellectual disability, prominent forehead, more severe in males

Question 12

Polygenic Inheritance - Definition

Answer 12

Traits influenced by multiple genes + environment (multifactorial)

Question 13

Polygenic Inheritance - Examples

Answer 13

Schizophrenia, height, cancer, intelligence

Question 14

Schizophrenia - Genetic Basis

Answer 14

Polygenic, no single gene (0.5% prevalence)

Question 15

Schizophrenia - Key Symptoms

Answer 15

Hallucinations, delusions, disorganized speech

Question 16

Phenylketonuria (PKU) - Inheritance

Answer 16

Autosomal recessive (chromosome 12)

Question 17

Phenylketonuria (PKU) - Treatment

Answer 17

Phenylalanine-free diet prevents intellectual disability

Question 18

Phenotype vs. Genotype

Answer 18

Phenotype = observable traits; Genotype = genetic code

Question 19

Range of Reaction

Answer 19

All possible phenotypes for a genotype across environments (e.g., yarrow plant height varies by elevation)

Question 20

Epigenetics - Definition

Answer 20

• Genome: record of the genetic material of an organism encoded in DNA
• Epigenome: record of the chemical changes to the DNA and histone proteins of an organism
• 基因组：记录生物体DNA编码的遗传物质
• 表观基因组：记录生物体DNA和组蛋白的化学变化

Question 21

Epigenetics - Role in Autoimmune Diseases

Answer 21

Environmental factors (smoking, UV) alter gene expression, contributing to diseases like lupus

Question 22

Regulator Genes

Answer 22

Control timing of gene activation/deactivation

Question 23

Sex-Linked Inheritance Examples

Answer 23

Fragile-X, hemophilia, red-green color blindness