6 Population Genetics

Question 1

What is population genetics?

Answer 1

Population genetics refers to the genetics of a large groups of individuals. It is typically concerned with gene and genotype frequencies, the factors that tend to keep them constant and the factors that tend to change them in populations.

Question 2

What are the assumptions of the Hardy-Weinberg principle?

Answer 2

Large population, random mating, no effect on reccurent mutation, no selection against phenotype, no migration in or out of population, autosomal locus

Question 3

When is the Hardy-Weinberg formula used in clinical settings?

Answer 3

Used to calculate carrier frequency

Question 4

Hardy-Weinberg

Answer 4

Two alleles (p and q) - p + q = 1 , genotype frequencies are caculated using p^2 + 2pq + q^2 =1

Question 5

When is the Hardy-Weinberg formula used?

Answer 5

We use this equation to determine the carrier frequency for rare autosomal recessive disorder

Question 6

What does p^2 equal?

Answer 6

p^2 equals the fraction (percentage) of the population with two normal alleles

Question 7

What does 2pq equal?

Answer 7

2pq is the number of carriers in the population

Question 8

What does q^2 equal?

Answer 8

q^2 equals the fraction (percentage) of individuals with the disease

Question 9

What are exceptions to Hardy-Weinberg?

Answer 9

Non-random matting (stratification, assortative, consanguinity) and Small populations (Inbreeding, genetic drift, founder effect)

Question 10

What is the difference between inbreeding and consanguinity?

Answer 10

Inbreeding is within a small geographic region (you don’t know you are related)

Question 11

What is genetic drift?

Answer 11

In a small population, allele frequencies may change just by chance

Question 12

What is founder effect?

Answer 12

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

Question 13

Cystic Fibrosis

Answer 13

Causes defect in chloride channel function (think mucous). Most common in Caucasians of Northern European descent. Heterozygotes may have protection against diarrheal diseases such as cholera and typhoid

Question 14

Sickle Cell Anemia

Answer 14

High incidence in Africans from the equatorial region, corresponds to high rate of malaria, single point mutation in B-hemoglobin that changes a glutamic acid to valine. Carrier frequency is 1 in 13

Question 15

Tay-Sachs Disease

Answer 15

Severe neurodegnerative disorder due to defective activity of hexosaminidase A (this enzyme degrades lipids in neurons). High incidence in Jewish indviduals of Ashkenazic (Eastern European) descent. Fatal disease, not treatment. Small, isolated communities breeding restricted to those of the same faith/ethnicity

Question 16

Maple Syrup Urine Disease in Mennonites

Answer 16

Maple syrup urine disease is an inborn error of leucine, isoleucine, and valine metabolism (causes neurotoxi symptoms in the first few weeks). Incidence is very high in Mennoites of the Eastern US. Likely due to genetic drift/founder effect in small population (marriage restricted to those of the same faith)

Question 17

Navajo Neurohepathopathy

Answer 17

Degenerative neurologic disease with hepatic and/or neurologic dysfunction. Due to mutation in the MPV17 gene which is important in mitochondrial function. The frequency fo the MPV17 kiley increasd due to genetic drift/founder effect