Breeding & Genetics (4-6)

Question 1

annual rates of genetic improvement in polygenic traits depend on what 4 main factors

Answer 1

1. selection intensity achieved (i)
2. accuracy with which genetic merit in the trait of interest is predicted (r)
3. the amount of additive genetic variation in the trait of interest (sdA)
4. the generation interval (L)

Question 2

the annual response to selection (R) can be predicted using this equation

Answer 2

R = (I x r x sdA) / L

Question 3

the higher the selection intensity, accuracy and genetic variation & the lower the generation interval, the (higher or lower?) the annual rate of genetic improvement

Answer 3

higher

Question 4

what is the main advantage of progeny testing

Answer 4

provides accurate predictions of a bull’s genetic merit based on the performance of daughters in commercial herds

Question 5

what are 2 disadvantages of progeny testing

Answer 5

costly & results take many years to materialize

Question 6

this the of selection depends on having records of performance on the candidates for selection, or their relative, or both

Answer 6

objective selection

Question 7

these are the 3 most important components of the breeding goal for meat production in beef and sheep

Answer 7

reproductive performance, growth, and carcass composition

Question 8

these are the 3 most important components of the breeding goal for milk production in sheep

Answer 8

reproductive performance, milk yield and milk composition

Question 9

deleterious consequences may arise in these 4 ways

Answer 9

1. by chance
2. as result of small/inbred populations
3. direct or indirect consequence of breeding goal being pursued
4. combo of these

Question 10

what are 3 potential responses to deleterious consequences arising

Answer 10

1. effective management of breeding populations
2. monitor breeds/lines for unforeseen consequences of selection
3. ensure breeding goals are aligned with appropriate production systems

Question 11

the decline in performance in traits associated with fitness due to the mating of two related animals

Answer 11

inbreeding depression

Question 12

this is defined as the probability that two alleles at any locus are ‘identical by descent’ (abbreviated F)

Answer 12

inbreeding coefficient

Question 13

formula for calculating the inbreeding coefficient (F)

Answer 13

𝛴(1/2)^n

Question 14

the rate of inbreeding (𝚫F) per annum can be calculated with this equation

Answer 14

𝚫F per annum = 1/8mL^2 + 1/8fL^2
(m&f = total numbers of males and females entering the population each year; L = average generation interval)