Genetics_of_polled_horned

The information about how an animal (or a plant) is built is stored in the chromosomes in the nucleus of the cells. The information for an individual feature is called a gene. Normally, there are two sets of similar chromosomes in every cell. Hence, every gene for a certain feature exists twice in every animal.
The gene which is responsible for the horns of a goat works like a switch with two positions: One position is for "horns" (p-), the other position is for "polled" (P+). If the two genes for "horns" or "polled" are identical on both chromosomes (P+P+ or p-p-), the goat is HOMOZYGOUS, If they are different (P+p-), the goat is HETEROZYGOUS.
The gene for "polled" (P+) is dominant over the gene for "horns" (p-). Consequently, all goats which carry at least one P+ gene are polled, and only those goats where both genes are p- have horns.
Because the gene for "polled" is closely linked to a recessive gene that creates hermaphrodites (inter-sexes) in females, does where both genes are P+P+ are infertile. This is the reason why it is not possible to breed for polled goat.
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