covAM

Dear Arthur et al

In the new ASReml manual on page 103 there is an example of a pin file
suggesting that the phenotypic variance is the sum of VA, VM and twice the
covariance between A and M (where A is additive genetic and M is maternal
genetic effect). However, the genetic covariance between direct and
maternal effects as expressed in one phenotype is always the result of A
and M coming from two different animals, with an additive genetic
relationship between them of 0.5.
So, the covariance between A and M in the same animal is 0.5*cov(A,M).
and var(P)=var(A+M+E)= VA + VM +2*0.5*cov(A,M) + VE
                = VA + VM + Cov(A,M) + VE

Therefore, if I'm correct, the appropriate coefficient in the pin file
should be one, not two.
I hope I am correct.

Julius
Received on Tue Dec 21 2004 - 15:56:13 EST