Lecture 3

Question 1

Why do we model genotypic effects from allelic values?

Answer 1

Because individuals pass on alleles not genotypes

Question 2

What are the average allele effects?

Answer 2

The average deviation of individuals who received the allele from one parent and the other allele randomly from the population.

Question 3

What are breeding values?

Answer 3

Summation of the average allele effects, they are additive. They depend on a and d, because alpha=a+(q-p)d.

Question 4

What is the equation for genotypic variance?

Answer 4

Genotypic variance = additive genetic variance + dominance variance

Question 5

Explain the concept of genetic drift.

Answer 5

Under random mating, no mutations and no migration:

• in large populations allele frequencies remain constant over generations
• in small populations allele frequencies change by chance aka random drift

Question 6

What two things does random drift cause?

Answer 6

Increase in homozygosity

Reduction in genetic variance

Question 7

In small populations, what is related to genetic drift?

Answer 7

Inbreeding

Question 8

What does the inbreeding coefficient tell us?

Answer 8

The probability that two alleles in a locus are identical by descent (allele came from the same ancestor)

Question 9

What is does it mean to be identical by descent? (In reference to new inbreeding and genetic drift)

Answer 9

The probability of two gametes taken from the population carry identical alleles from the same ancestor.

Question 10

What is the definition association with old inbreeding in reference to genetic drift?

Answer 10

Probability of two gametes taken randomly from the population from different ancestors carry identical by descent alleles.

Question 11

What are the 4 conditions and 2 characteristics of two unlinked loci? What do these conditions mean in terms of possible gametes?

Answer 11

In large populations under random mating, no selection, no mutations and no migration.
The two loci are in: HW equilibrium within locus and joint gametic phase equilibrium.
Means that the probability of possible gametes are given by the product of allele frequencies, because alleles are independent.

Question 12

How do two unlinked loci behave in disequilibrium?

Answer 12

D is halved by one generation of random mating

r=0.50

Question 13

How do two linked loci behave in disequilibrium?

Answer 13

When r=0.5 they behave like unlinked loci where one generation of random mating halves D.
When r<0.5 it will take longer to reach equilibrium by random mating