Proving Dominant Traits

[paulh]

A few years ago I helped a professional geneticist work on his hobby project -- a similar project on the crested mutant gene in zebra finches. He mated crested x crested to try to get homozygous crested of both sexes. Then he mated the possible homozygous crested to a normal of the opposite sex. When normal offspring occurred, he marked that possible homozygous crested as a known heterozygous crested. He ended the project with 25 matings that produced either normal offspring or both crested and normal offspring. Zero matings produced only crested.

My point is that 5-10 matings are insufficient for the statistics.

[gsarchie]

My point is that 5-10 matings are insufficient for the statistics.

I don't think anyone is arguing that an "n" of 5 or 10 would be sufficient, are they?

I've never heard of the wz before but I was looking at a breeder's pairings online and saw where a spider male produced both male and female spider offspring when bred to a normal female, so there goes that theory.

[RandyRemington]

Paul, so after 25 33% chance possible homozygous animals in a row failed to prove did the breeder decide it's a homozygous lethal mutation? Did ya'll notice about 1/4 bad eggs from the het X het breedings or any infertile possible homozygous animals?

[paulh]

Paul, so after 25 33% chance possible homozygous animals in a row failed to prove did the breeder decide it's a homozygous lethal mutation? Did ya'll notice about 1/4 bad eggs from the het X het breedings or any infertile possible homozygous animals?

Yes, he decided crested was lethal when homozygous. The odds of getting that string of failures by chance was just too small. He also found that there were fewer crested zebra finches than normals from a crested x normal mating. This was when the results of many matings were totaled.

Part of what I did was to check the finch nests for eggs and nestlings. A clutch averaged 6 eggs. Three babies leaving the nest was considered good results. The other eggs were either infertile or dead embryos. Entire clutches might be abandoned. An egg was approximately 1/4 inch long, so hatchlings were tiny. Dead hatchlings were not recorded. They were lost in the nest material or litter on the cage floor. So we could not zero in on the stage of homozygous crested death. Sometime before feathering out was our best guess, which leaves plenty of time. Sterility in adults did not seem much of a problem.