Question

At a local piggery, the pigs have varying tail lengths with a herd mean of 18 cm, and variance of 8 cm2. The farmer crosses boars with a 6 cm tail to sows with a 30 cm tail. The mean tail length in the piglets is approximately 18 cm, with a variance of 1 cm2. If these piglets are allowed to interbreed the full range in tail lengths is restored and approximately 3 % of the piglets have extreme phenotypes. The farmer also selects a core group of pigs with a mean tail length of 10 cm, and when bred with the general herd, they produce piglets with a tail length of 13 cm.

Discuss the mode of inheritance of this trait, with reference to (i) the total genetics effects, (ii) the transmittable genetic effects, (iii) the effects of the environment, (iv) the number of genes involved and their mean allelic contributions (show all calculations).

Answer 1

i) The total genetic effect is the final phenotype from the more than one gene or from alleles of a single gene that combines in such a way the sum of in effects in is equal to the sum of their effects of insividuals.

ii) The transmittable genetic effect is the effect that transmitted from parents to the offsprings by the form of homologous chromosomes that contains a unique combination of DNA sequences that codes for the genes.

iii) effects in the environment which will mainly cause at the juvenille stage.