Banana

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Originally Posted by OhhWatALoser

There's nothing to suggest it is a dominant gene besides it's misclassification being repeated and rumors of super spiders that never seem to be able to prove themselves

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I agree.

The only thing we are sure of is that spider is not a recessive mutant gene.

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Originally Posted by OhhWatALoser

Perhaps Paul could add to this but from what I understand, Sex chromosomes in snakes are known to be Z and W. Males are ZZ and females are ZW (opposite of the human XY male and XX female). so when a male breeds to a female, you can get 1 of 2 Z chromosomes from the male and either another Z or a W from the female. So a simple sex linked gene will either be linked to Z or W

W linked gene is the easiest, only females can have it, any female produced from a female who has it will also have it. Male will never have it, ever.
Z linked gene females can have the heterozygous and males can have both heterozygous and homozygous. Females who have it will produce females without it and males with it. Heterozygous male will throw normal ratio. Homozygous male will throw normal ratio. Homozygous male to heterozygous female will only throw super males and heterozygous females.

Now bananas on the other hand.... well are doing something never seen before. They kinda act sex linked as we have males that throw skewed ratios and the whole 10% of the time bananas throw the opposite sex thing could be explained by crossing over, which does happen, but the big monkey wrench is as with my above example it should be expected that females would be the ones throwing skewed ratios, not males. the gene is acting like a XY sex linked gene with crossing over and not a ZW. So we could blindly say ball pythons are XY. As far as I know ZW has not been identified in ball pythons.

However ZW has been identified in burms and we know ball pythons breed fine with burms. As far as I know there has never been a snake found to have XY and I don't even know of a reptile that is XY however I never looked that deep either. Basically from the dinosaur era and before, snakes have been ZW. There are reptiles that determine sex through other means such as temperature, but if there is identifiable sex chromosomes it has always been ZW as far as I know. So long story short, if we call it sex linked we are suggesting that ball pythons are XY after having an enormous line of ZW ancestors and a ZW close relative (burms) that they can reproduce with, solely based on the evidence of a gene. I think it is pretty short sighted to make that leap.

So when people ask about banana being sex linked, I say the evidence currently doesn't support that. When talking about genetics and referring to sex linked genes, people expect the above scenarios, so even saying it is not sex linked isn't really wrong lingo wise. However someday maybe someone can possible figure out the riddle and maybe the gene actually does reside on a sex chromosome, but it would be a special case with the abnormalities surrounding it.

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Thank you for explaining. I love learning new things and I do learn another one from you.

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Originally Posted by paulh

To expand a bit on OhWatALoser wrote:

In the normal type of sexlinkage, our malemaker banana royal python has two Z chromosomes (ZZ). One Z has the banana gene, and the other has the corresponding normal gene. We can symbolize this as ZZ. The red Z has the banana gene, and the black Z has the normal gene. This male is mated to a normal female with the ZW chromosome pair. Both the Z and W are in black. The Z chromosome has the normal gene, and the W has either the normal gene or no corresponding gene.

A ZZ male is mated to a ZW female. In a fertilized egg, the male's normal Z chromosome pairs with either the female's Z or the female's W chromosome. The male's Z chromosome can also pair with either the female's Z or the female's W chromosome. This produces 4 possible chromosome pairs:
ZZ = banana male
ZZ = normal male
ZW = banana female
ZW = normal female

We expect about half of the bananas to be females. But according to Mike Wilbanks, only about 10% of the bananas from this mating are females. Why the excess of male bananas? We can only conclude that something unexpected is going on.

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I like the simple explanation with red color. It makes learning easier. Thanks!

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Originally Posted by Deborah

Female Bananas or CG produce normal sex ratios.

When it comes to males, a male from Banana or CG sire will be a male maker. A male from a Banana or CG Dam will be a female maker.

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Ok noted and thanks. Now I at least understand what to expect from a male or female maker BP.