29) Quantitative population genetics in breeding

Question 1

Regression

Answer 1

• Gives the measure of the association between:
  
  • The dependent variable
  • The independent variable
• Usually formed in an equation

Question 2

Regression toward/to the mean

Answer 2

• If a variable is extreme on its first measurement
• It will tend to be closer to the average on it’s second measurement
• If it is extreme on its second measurement, it will be closer to the average on its first

Question 3

Galton’s regression

Answer 3

• Sir Francis Galton
• Observed extreme characteristics e.g. height in parents are not passed on completely to their offspring
• Characteristics of the offspring regress towards a mediocre point (mean)

Question 4

Heritability estimate

Answer 4

• Single trait measured on animals in a specific population at a given point in time
• Estimated from performance record and pedigree information
• Can differ between breeds and may change slowly over time

Question 5

How many definitiions of heritability estimate are there?

Answer 5

4

Question 6

Heritability estimate definition 1

Answer 6

Measure the degree to which offspring resemble their parents for a specific trait (0-100%). Extend to all genetic relationships, e.g. siblings

Question 7

Heritability estimate definition 2

Answer 7

Measure the strength of relationship between performance (phenotype) and breeding value (genotype) of an individual animal

Question 8

Heritability estimate definition 3

Answer 8

• Measure the expected differences in the breeding value of an animal for each unit of difference in that animal’s phenotype for a particular trait (important in understanding the role of heritability in predicting the response to selection)

Question 9

Heritability estimate definition 4

Answer 9

• The ratio of causes of variations between animals
• Proportion of the total (phenotypic) variations.
• Explained by the genetic variation and is attributable to genetic variation among individuals and that is transferred from generation to generation.

Question 10

Broad-sense heritability

Answer 10

• Reflects all possible combinations to population phenotypic variance
• H2 = Var (G) / Var (P)

Question 11

Narrow sense heritability

Answer 11

• Includes variances caused by genetic and environmental factors
• h2 = Vg + Vp
• Response to selection realized heritage.

Question 12

Family units used to estimate heritability most commonly include…

Answer 12

• Parent & offspring
• Parents & offspring
• Full siblings
• Paternal half-siblings

Question 13

Heritability=

Answer 13

V_genetic / V_phenotypic

Question 14

V_phenotypic =

Answer 14

V_genetic + V_environment

Question 15

V_genetic=

Answer 15

V_additive + V_{dominant/recessive} + V_{other allelic interactions}

Question 16

V_environment=

Answer 16

V_permanent + V_temporary

Question 17

Heritability estimates are useful for…

Answer 17

• Breeding value estimation
• Prediction of selection response
• Helping decision of selection method
• Choice of mating period
• Prognostic of result of crossbreeding