Population Genetics

Question 1

What is an inbreeding coefficient?

Answer 1

The probability that 2 copies of a gene are inherited by descent from the same ancestral source.

Question 2

What is inbreeding depression?

Answer 2

Inbreeding can result in sick animals, but can also compromise the ‘fitness’ of the whole inbred line e.g. fertility traits.

Question 3

What is the rate of inbreeding?

Answer 3

Change of average inbreeding coefficient over time.

Question 4

What is the effective population size? How is it related to rate of inbreeding?

Answer 4

No of breeding individuals in a hypothetical random mating that would have the same rate of inbreeding seen in a real population. 1/(2 x rate of inbreeding)

Question 5

What are the two important ways of measuring/controlling inbreeding?

Answer 5

Constrain the rate of inbreeding to no more than 0.5% per generation, and keep effective population size about 100 at least.

Question 6

What is selection intensity?

Answer 6

The difference between population mean and the mean of selected individuals.

Question 7

What does PTA stand for?

Answer 7

Predicted transmitting ability

Question 8

What are selection indexes? Give an example of some.

Answer 8

Combinations of PTAs, which weigh multiple desirable traits e.g. PIN index, profitable lifetime index (PLI)

Question 9

What is the difference between PIN indexes and PLI (profitable lifetime) indexes?

Answer 9

PIN index measures production traits only. PLI measures production + other traits such as lifespan, SCC, locomotion, fertility, calving ease etc.