The polled gene is luckily one of cattle breeding simpler genes to understand; it is a single gene so the inheritability is straight forward.   A a rule genes come in pairs, and fortunately the polled is dominant to the horned gene.

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A polled animal that has two copies of the polled gene is know as homozygous polled and this animal mated to horned animals will produce 100% polled calves.  These calves will have inherited a copy of the polled gene and a copy of the horned gene from each parent.  These polled animals that carry the horned gene are called heterozygous polled.

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Homozygous polled is often indicated as PP, so can only pass on the dominant polled gene.

Heterozygous polled is often indicated as Pp the small p indicates the horned gene. This animal will pass on either (randomly) a polled gene or a horned gene two its progeny. So mated to horned animal you will expect 50% polled and 50% horned.

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For a more detailed explanation Signet have the following useful article...... click here

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