Quote Originally Posted by Kcl View Post
I had to look into this because I'm no expert on ball python genetics. Step 1 is determining what sex chromosome system they follow. The problem is that many snakes have been determined to be ZW where the female is the heterogametic one (having two different chromosomes). However, this doesn't match up with the inheritance pattern for coral glow.

While I haven't quite finished reading this paper (working on it), it looks like the coral glow gene was part of the basis of this 2016 paper that showed that pythons feature the XY inheritance system. If they're using the XY inheritance system, coral glow may well be just sex-linked, with the rare exceptions for male or female maker bananas throwing the opposite sex bananas being a case of cross-over.

https://www.researchgate.net/publica...cationCoverPdf

It was previously assumed that all snakes were ZW. Working off that assumption, coral glow/banana's inheritance pattern doesn't fit any normal sex-linked inheritance.

But if it's XY, then yes, it could be the following:

Banana female x normal male: X(b)X(n) x X(n)Y - makes X(b)X(n), X(b)Y, X(n)X(n), X(n)Y.
Normal female x banana male (from banana female) - X(n)X(n) x X(b)Y - makes X(n)X(b), X(n)Y.
Banana male (from banana male) x Normal female - X(n)Y(b) x X(n)X(n) - makes X(n)Y(b), X(n)X(n).

Although in that case I'd speculate that the gene started on the Y chromosome and ended up crossing over to the X and is in a location where crossover is relatively frequent, also explaining the exceptions. But that's entirely speculation.

EDIT: Also a thing to note is that usually a sex-linked gene doesn't show up on BOTH the X and the Y chromosome or else it wouldn't really be demonstrating the sex-linked trait in the first place. The classic examples like color-blindness are found solely on the X chromosome.
Damn.....


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