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Posted by Paul Hollander on January 31, 2003 at 19:01:19:
Back before Christmas, someone posted a picture of a male brindle black rat snake. It confirmed a report I'd heard that brindle males are considerably lighter than brindle females.
There is a mutant named faded in pigeons and a mutant in pilgrim geese that cause the females to be lighter in color than normals and the males to be lighter than the females. Both mutants are sexlinked. IOW, males have two large sex chromosomes, each one symbolized Z. Females have one large (Z) sex chromosome and one small (W) sex chromosome. Colubrid snakes also have the ZZ male ZZ and female ZW sex chromosome pattern. The mutant is located on the Z chromosome, and there is no corresponding gene on the W chromosome.
Note: The male ZZ and female ZW chromosome pattern is the reverse of the mammalian sex chromosome pattern, where males are XY and females are XX. With the mammalian X being much larger than the Y chromosome.
If brindle is a parallel to pigeon and pilgrim geese mutants, it is the first sexlinked mutant to turn up in snakes.
If brindle is sexlinked, then females are either brindle or normal. While there would be heterozygous brindle males, there would be no females that look normal yet carry the brindle gene. And brindle would show the following mating patterns:
1) brindle male x brindle female --> all males and all females brindle
2) brindle male x normal female --> all males normal (heterozygous brindle), all females brindle
3) heterozygous brindle male x brindle female --> half the males brindle, half the males normal (heterozygous brindle), half the females brindle, half the females normal.
4) heterozygous brindle male x normal female --> half the males normal, half the males normal (heterozygous brindle), half the females brindle, half the females normal.
5) normal male x brindle female --> all males normal (heterozygous brindle), all females normal.
Mating 2 is the key to proving sexlinkage. Though I probably will not be able to get on the net over the weekend, I'd really like to hear the experiences of brindle breeders who have mated a brindle male to a normal female.
And for those with either brindle males or heterozygous brindle males who haven't made this mating, you can add cheap normal females to the breeding group. This would be an easy way to increase the production of female brindles. 8-)
Paul Hollander
