2. Principles Of Population Genetics

Question 1

Discuss genetic variation in populations (objective)

Answer 1

Answer later

Question 2

Calculate allele and genotype frequencies (objective)

Answer 2

Answer later

Question 3

List the assumptions required for the Hardy-Weinberg Law (objective)

Answer 3

Answer later

Question 4

Discuss each of the exceptions to the Hardy-Weinberg Law (objectives)

Answer 4

Answer later

Assortative Mating
Consanguinity and Inbreeding
Genetic Drift and the Founder effect
Heterozygote advantage and selection

Question 5

Highlight the important genetic issues in selected populations (objective)

Answer 5

Answer later

Cystic Fibrosis
Sickle Cell Disease
Tay-Sachs Disease
Maple Syrup Urine Disease
Navajo Neurohepatopathy

Question 6

Populations

Answer 6

Large groups of individuals
-typically concerned with the gene and genotype frequencies, the factors that keep them constant and the factors that tend to change them in populations

What is the frequency of p or q allele?
What is the frequency of p2, 2pq, q2?

Question 7

Hardy-Weinberg Principle (overview)

Answer 7

Way of predicting genotype frequencies from allele frequencies

Assumptions:
Large Population
Random Mating
No effect of recurrent mutation
No selection against any phenotype
No migration in or out of the population
Autosomal locus

Under assumptions, gene and genotype frequency do not change from generations

Question 8

Hardy-Weinberg Principle (equations)

Answer 8

Assume two alleles: p and q
p+q=1
p2 + 2pq + q2 = 1

p2, q2 are homozygote genotype frequencies
2pq is heterozygote genotype frequency

*USE for Autosomal Recessive Disorders

Question 9

Hardy-Weinberg Law (two carriers have children)

Answer 9

(2pq)x(2pq)x(1/4)

1/4 is chance of having a recessive genotype child

Question 10

Medically Important Exceptions to Hardy-Weinberg (list)

Answer 10

Nonrandom mating

• stratification (racial, ethnic, religion)
• assortative (i.e. Deaf marry deaf)
• consanguinity (relatives in common)
  
  • does not change allele frequency, greater risk of having homozygous (i.e. Middle East)

Small populations

• Inbreeding
  
  • Genetic Drift
  • Founder Effect

Question 11

Inbreeding

Answer 11

Differs from consanguinity (know that relatives related, subset of inbreeding)

Mating within a small geographic region, etc

Question 12

Genetic Drift

Answer 12

In small population, allele frequencies may change just by chance

(Chance which alleles get passed on, some individuals will die or do not reproduce)

Question 13

Founder Effect

Answer 13

If a mutation is present or arises in single individual, the frequency of the allele may increase in subsequent generations

Question 14

Cystic Fibrosis (genetic issues)

Answer 14

Caucasians (1:2500 births)
Defect in chloride channel function, thick mucous

Heterozygous advantage against diarrheal diseases such as cholera and typhoid

Question 15

Sickle Cell Anemia (genetic issues)

Answer 15

Africans from the equatorial region
Corresponds to high rate of malaria
Two HbS have anemia- “sickled” rbc’s. Cells obstruct capillary blood flow leading to intermittent painful crises
Heterozygotes are asymptomatic unless oxygen levels low (high mountains, airplanes), resistant to malaria protozoan

Hetero’s are selected for in malaria areas

Incidence for homozygotes in African Americans is 1:625, carrier is 1:13

Single point mutation in B-hemoglobin that changes a glutamic acid to valine (propensity for hemoglobin to polymerize under low oxygen tension)

Question 16

Tay-Sachs Disease (genetic issues)

Answer 16

Severe neurodegenerative disorder due to defective activity of hexoaminidase A (enzyme degrades GM2 gangliosides which are lipids in neurons
Ashkenazic Jews
Fatal, no treatment

Small, isolated communities with breeding restricted to those of the same faith/ethnicity

Question 17

Maple Syrup Urine Disease (genetic issues)

Answer 17

Neurotoxic symptoms in first weeks of life

Inborn error of leucine, isoleucine and valine metabolism (one enzyme affecting 3 aa’s)

High incidence in Mennonites of Eastern U.S. (PA OH IN)

Likely due to genetic drift/founder effect in small population (marriage restricted to same faith)

Question 18

Navajo Neurohepatopathy (genetic issues)

Answer 18

Degenerative neurologic disease with hepatic and/or neurologic dysfunction

Mutation in MPV17 gene (mitochondrial function)

Population reductions in Navajo because of US military

Frequency of MPV17 mutation likely increased due to genetic drift/founder effect