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Posted by Paul Hollander on February 01, 2003 at 14:39:37:
In Reply to: Re: Brindle, a sexlinked mutant in the black rat snake??? posted by meretseger on February 01, 2003 at 12:25:03:
:So.... it's kind of like color blindness in humans?
Yes. Color blindness in humans is a sexlinked mutant.
: I wonder if these snakes have 'barr bodies', where one of the female's W chromosomes is inactive in each cell?
First, the bird/colubrid Z chromosome is large, like the mammal X. And W is small, like the mammalian Y. And female birds/colubrids have a ZW set while males are ZZ. So if there is an equivalent of the mammalian barr body, it would be in males. IMHO, there is no barr body because a male brindle is significantly lighter than the female. And if only one Z was active in the male, I'd expect the brindle male to be the same shade as the brindle female, which has only one active Z chromosome.
:I had no idea there were any reptiles whose sex was chromosomally determined like it is in mammals and birds. Is it just colubrids or are there any other groups of snakes like that?
My opinion is that most if not all snakes have chromosomally determined sex. All the snake chromosome pictures that I've seen that had different sized sex chromosomes in the females were colubrids. The boa constrictor definitely does not have different sized sex chromosomes, and AFAIK, it's the same for all boids. But what other cause determines sex in the boa? AFAIK, boa breeders get an approximately 50:50 sex ratio.
Paul Hollander
