AGB 121: Principles of Animal Genetics and Population Genetics (2+1)

BREEDING VALUE (BV)

• The value of an individual, as measured by the average value of its progeny is called the breeding value of the individual .
• This is also the sum of the average effects alleles (a - alpha ) of the individual.

If an individual is mated to a number of individuals at random, from the population then its breeding value is twice the mean deviation of the progeny from the population mean (since the individual only contributes half of the alleles to its offspring) .

• Breeding value = the value of genes to progeny
• Genetic value = the value of genes to self

• It includes non-additive effects (such as dominance) which cannot be passed on to progeny

Genotype	Breeding value
A1 A1	2 a1 = 2q a
A1 A2	a1 + a2 = (q - p) a
A1 A2	2 a2 = -2p a

• The mean breeding value = 2p²q a + 2pq (q-p) a - q²p a = 2pq a ( p + q - p - q ) = 0 .
  • With random mating, the mean breeding value is zero.
• A (additive genetic effect) is also sometimes referred to as breeding value.