Today's interesting fact deals with lizards.

I've covered before how some lizards have sex determining genes, and others use the temperature of their surroundings while they are in the egg to determine their sex. With those who use genes to determine sex, Lizards and snakes have ZW chromosomes. Those with ZZ are male, those with ZW are female. It has been long thought that lizards with the set of WW chromosomes, were both infertile and non-viable (e.g. they die in the egg), just as mammals with YY sex chromosomes are non-viable and die in the egg.

Normally, when birds or lizards reproduce parenthetically, all the young are male, as the young are only produced from doubling the chromosomes of the mother. Females couldn't be born.

But recently, however a Boa Constrictor, an India Python, has been found to have produced viable female young, with WW sex chromosomes. It is interesting that the Boa produced no male offspring, only female ones.

This is being studied now, and they are hoping to determine if the mother's offspring can produce offspring from mating with males. If they do, they should also be female. Only the Boa's grandchildren should produce males after mating.

I look forward for the next few years to find out the outcome.