Reptile & Amphibian Forums

could someone please explain to me the difference between dominant and co-dominant, because both breed to a normal would produce about 50% of that morph. Sorry if this is a stupid question

Thanks
Bob

With a dominant trait, the heterozygous and homozygous phenotypes are identical. With a co-dominant trait, the heterozygous and homozygous phenotypes are different.
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Louis Kirkland
Cornerstone Reptiles

An example of CoDominant is the Pastel morph.
You could have a regular Pastel which is heterozygous for that gene (Pp).
Or you could get a Super Pastel which is homozygous for that gene (PP).

Whereas in the case of a Dominant morph you cannot tell the difference between the heterozygous and homozygous states. Such as a Spider (which is currently considered dominant). A het and a homozygous individual would both just be "Spiders", and you couldn't tell just by looking at it what its genes are.
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1.0 normal ball python
0.1 greyband hybrid kingsnake
0.2 crazy cats
1.0 husband
Omaha Reptile Breeder's Expo: April 19th.

OK, so a easy way to tell the difference is this. Example 1- IF you breed a spider ball X spider ball you get all spiders (dominant) example 2 - Yellow belly X yellow belly, statisticly you should get 75% yellow bellies and 25% ivorys ( co-dom) The ivory being the super form of the yellow belly. So if you can make a different looking animal with a same X same breeding (super form) you have a co-dom. In theory

Kyle

Your theory is kinda correct but the math is wrong. a spider x spider (in theory) would produce 3/4 spiders (with each having a 1/3 shot of being homozygous spider) and 1/4 normals. The yb x yb would produce 1/4 ivory, 1/2 yb, 1/4 normal.

Thanks I understand better now. I have just been trying to do some punnet squares and im not always sure what the letters to use are, for example if you had a spinner X super pastel could you use a four box square and if so what letters would you use for a spinner

Thanks for all of your help
Bob

When writing up a punnett square, you need a box with however many possible combinations of genes. Whichever letters you choose is completely arbitrary.

your example, spinner x super pastel:
S = spider, s=normal at spider loci, P=pastel, p= normal, N=pinstripe, n=normal

Now since there are 3 genes in this cross (spider, pin, pastel) you need to take into account all 3 of them.

There are 4 combinations of genes in each gamete possible for the spinner: SNp, Snp, sNp, snp. So there will be four columns along the top with each column headed by one of those gene combinations.

The super pastel only has one gene combination possible: snP.

So for this breeding, you would have a 4 x 1 box.
You end up with 1/4 SsNnPp (spinner blast), 1/4 SnnPp (bumblebee), 1/4 ssNnPp (lemon blast), 1/4 ssnnPp (pastel).