Prepotency is and excellent conversation and very appropriate to this thread!
... If the genes are sex-lined, they come from the sire or from the dam's sire.
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Now, genes are either dominant, which means you can see them with only one dosage from one parent, or they're recessive, which means that a chick needs the same gene from both parents for it to be visible, i.e. part of its phenotype. If a recessive gene is paired with a dominant gene, it's still present, it's just invisible.
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Now this is considering dominants vs. recessives and the possibility of outcross, but within a given strain, one has modifiers working on a pattern or on a body structure. Many, many qualities are had by modifiers which are called quantitative, meaning they are the product of a breeding program.
Eventually one risks getting a cockerel that is homozygous for all of the necessary parts and that has a very high level of quantitative modifiers to pass around. His offspring are like BAM, because he is a genetic powerhouse. He can make up for the failings of his mates because of his homozygous prepotency and high volume of quantitative modifiers. Now, in theory, a hen can also be prepotent, but she will always be at the disadvantage when it comes to any sex-linked quality because a hen can only pass on a sex-linked quality to male offspring whereas a male can pass on a sex-linked quality to both male and female chicks. Also, the prepotent male is particularly valuable because it can be so easily spread about in the breeding pen(s).
The importance of modifier accumulation cannot be overstated, thus Dragonlady is always mentioning "Having a picture in your mind of what you're going for." One must continue to select in a specific direction in order to accumulate the various modifiers that are going to give that certain je ne sais quoi to your strain. If you keep changing your imagined ideal, your modifier accumulaton will be like a roller coaster ride, and your stock will lack consistency. Whenever you see a strain that's not simply, as Bob would say, a 92 point bird, what we refer to as being "representative of the breed", meaning, yeah, all the brids are rose combed, all white, all white skinned, etc..., but when you see a strain where each bird is consistent with the others and each quality just seems to stand out at you like a neon sign of "excellence", this happens because the modifiers have been uniformly accumulated throughout all the birds, and they are genetically very similar for the desired traits.