Posted: Tue Aug 10, 2010 7:08 am
What are the genetics of polled animals? If a polled cow is served by a horned bull, will the offspring be polled or horned?
The polled gene is dominant, so it only needs the presence of one polled gene to make the offspring polled.
The horned bull must carry two horned genes, because if he carried a polled gene he would not be horned.
So if your polled cow is heterozygous (ie carries one polled gene and one horned gene) then she will pass on the polled gene (on average) to 50% of offspring - so with the horned bull 50% will be polled.
If the cow were homozygous (ie two polled genes) then 100% of offspring would get a polled gene and would be polled.
Two heterozygous parents will produce 75% polled offspring, and 25% horned.
Two homozygous parents will only produce polled offspring.
Have a look at the article "Some genetic simplicity" in the Winter 2009 issue of "The Bulletin"
Duncan