I'll explain further.
Cameo female X Purple male = Purple daughters and IB split to Purple and Cameo sons
Purple female X Cameo male = Cameo daughters and IB split to Purple and Cameo sons
Note that sons from both crosses will be the same for breeding purposes. Now take a son from either cross above and breed to an IB hen.
IB female X IB split to Purple and Cameo male
The daughters from the cross above will get their Z from
only their father. As-is, their father has one Z with the Purple mutation, and the other with the Cameo mutation. Both are on the Z chromosome, but at different locations, or
loci. Now, keep something else in mind -- the Z with the Purple mutation will also have the "normal" or "non-Cameo" version of the gene of which Cameo is a mutation, and the Z with the Cameo mutation will also have the "normal" or "non-Purple" version of the gene of which Purple is a mutation.
OK, so now to introduce the phenomenon of
crossover. I linked the Wikipedia article on it because I don't want to repeat myself again out of consideration to those who have read my descriptions of it before. I do want to note that
this is a known phenomenon and not some crazy made-up thing. It happens. We know it because it's been studied for decades.
So this IB split to Purple and Cameo male will be making some sperm. Each sperm has one member of each pair of chromosomes contained in his body cells, but
which member of the pair will be random. And often, the chromosome will be a recombined version made from pieces of both pairs stitched together after crossover. If the Zs crossover at a point between the loci for the Purple and Cameo mutations, the result would be two newly recombined Zs -- one with both mutations, the other with neither. In other words, the original two Zs were one with Purple and "non-Cameo", and the other with "non-Purple" and Cameo. Recombined, you'd get one with Purple and Cameo (i.e. "Peach"), the other with "non-Purple" and "non-Cameo" (i.e. "normal IB").
OK, now let's get back to breeding the next generation.
IB female X IB split to Purple and Cameo male =
Daughters -- Purple, Cameo, IB, Peach
Sons -- IB split to Purple, IB split to Cameo, IB split to Peach, IB
I chose an IB female to focus on the only variable which concerns this discussion -- how Purple and Cameo together become Peach. As-is, the male above can pass on a Z with Purple or a Z with Cameo. Adding crossover possibilities, he can also pass on a Z with
both Purple
and Cameo (i.e. "Peach"), or a Z with
neither Purple
nor Cameo (i.e. "IB"). Because his daughters don't get a Z from their mother, her color in this situation doesn't matter.
How often will crossover occur at a point between the Purple and Cameo mutation loci? I don't know. It depends on the relative distance between the two points on the Z chromosome -- the greater the distance, the more places for crossover to occur between them. In other species, genes described as being "tightly linked" don't separate often because they lie close together on the chromosome -- thus less space for (and fewer chances of) crossover occurring between them. Considering the accounts of the original breeder of Peach, the two mutations aren't very close together, since the mutations came together in the first and second clutches.
You'll find some of my other ramblings on the inheritance of Peach by searching through old threads here. My former username was AquaEyes. I linked those discussions in the post below.
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