Genetic model for quantitative traits

Question 1

Simply inherited traits

Answer 1

traits affected by one or few genes (coat color , presence of horns, genetic defects like spider syndrome in sheep)

Question 2

Polygenic traits

Answer 2

traits affected by many genes (no single gene having an overriding effect) like growth rate , milk production, birth weight, etc.
affected by the environment.

Question 3

what does P= u + G + E stand for

Answer 3

P= phenotype value of an animals for given trait
U - population mean or average phenotypic value for the trait of all animals in the population
G= the genotypic value of the animal for the trait
E = the effect of the environment factors on the phenotype of the animal
G and e are expressed a deviations from the mean of the population. Therefore, the mean of G in the population and the mean of E is equal to zero.

Question 4

Genotypic value -

Answer 4

the overall effect of all the genes carried by the animal ( singly and in combination) on the phenotype of the animals for the trait.

Question 5

Breeding value

Answer 5

the part of genotypic value that can be transmitted from parents to offspring.