Reptile & Amphibian Forums

What actually happens when you cross a homo for super pastel with a homo normal?

If the allele for superpastel (or hypomelanism, tiger, or striped) is co-dominant to normal as some people have suggested, 100% of the offspring would appear pastel. Here’s why:

NN=normal
NP=pastel
PP=super pastel

NN x PP= NP NP NP NP=100% pastel.

Also, if traits like stripes, tiger, pastel, and hypo were codominat, they would occur very frequently naturally. Think of human blood types again. Type AB is the most common, then Type A and B occur less frequently in the same ratios, and type O is the rarest.

Remember, codominat alleles are equally expressed. A dominant allele is ALWAYS expressed if present. Now also consider a cross between a hetero for a known recessive trait, say HYPERmelanism, and a hetero for HYPO assuming hypo is codominant with normal.
N=normal
n=hyper
H=hypo

Nn x Hn = NH Nn Hn nn=2hypo:1normal:1hyper

Or a cross between a homo for hypo with a homo for hyper:
HH x nn=Hn Hn Hn Hn= 100% hypo

These things DO NOT happen.
Paul

"Or a cross between a homo for hypo with a homo for hyper:
HH x nn=Hn Hn Hn Hn= 100% hypo

These things DO NOT happen."

If you cross a super tiger retic (homozygous for the codominant trait) with an albino retic, all the babies will be tiger retics that are het for albinism. They'll basically be double het for each trait, the only difference is that they express the fact that they're heterozygous for super tiger, while the fact that they're het for albino is hidden.

Also, you said: "Now also consider a cross between a hetero for a known recessive trait, say HYPERmelanism, and a hetero for HYPO assuming hypo is codominant with normal.
N=normal
n=hyper
H=hypo

Nn x Hn = NH Nn Hn nn=2hypo:1normal:1hyper"

I think you've simplified this too much. I also think it's too confusing using hypo- and hypermelanism because those traits might cancel each other out. Let's look at a cross between a het albino retic Aa and a tiger retic Tt (note aa is an albino and tt is a super tiger). The genotypes you would get would be AATT, AaTT, AATt, and AaTt, or 25% normal, 25% het albino, 25% tiger, and 25% tiger het albino. There would be no albinos because only one parent could contribute the gene for albinism.

Jake

The two examples I used

HH x nn=Hn Hn Hn Hn= 100% hypo
Nn x Hn = NH Nn Hn nn=2hypo:1normal:1hyper

are not valid equations so I could see how they could be misunderstood. I wanted to show what would happen if there were two dominant genes in the equation.

I am not understanding a couple things myself. Here is your first example:
"If you cross a super tiger retic (homozygous for the codominant trait) with an albino retic, all the babies will be tiger retics that are het for albinism. They'll basically be double het for each trait, the only difference is that they express the fact that they're heterozygous for super tiger, while the fact that they're het for albino is hidden."

First, super tiger is a pattern trait not a pigment trait right? If it is then you are talking about two different traits that may or may not be linked. So, I have a super tiger retic, what would I cross that with pattern wise? I see you said cross it with an albino, but the albino doesn't tell me what its pattern genotype is. Secondly, in your next example you note that tt is super tiger and Tt is tiger. That is exactly what my main point is. Super tiger, or tt, is homo-recessive and not dominant or codominant at all.

The part I would get really messed up on is if you told me that if you cross a super tiger, tt, with a homo-normal patter, TT, you would get all super tigers. I'm not saying that doesn't happen mind you, I'm saying that if that is the case I would have to head back to the drawing board. There are still other factors to consider. For instance a sex influenced trait. An example in humans would be pattern baldness. In females it's reccesive but in males it's dominant(how unfair!).

Paul Kemes

I dont want to start a debate, but I would say you are completely wrong regarding the blood types. AB is not the most common and O is definately not the rarest.
This is how it is in Sweden, I presume it´s almost the same in the US. Or am I wrong!

A Rh(positive) (37%)
O Rh(positive) (32%)
B Rh(positive) (10%)
A Rh(negative) (7%)
O Rh(negative) (6%)
AB Rh(positive) (5%)
B Rh(negative) (2%)
AB Rh(negative) (1%).

Best regards

Henric Afors/Morelia Inc

Morelia Inc

The Rh factor is inherited separately from A, B, AB, or O blood types. When you are Rh positive, your red blood cells have a particular antigen, and when you are Rh negative, the antigen is absent.
P

In your example you mixed up the N (Normal) with the n (hyper).
That's why the breeding of the two different hets gives you a homozygous hyper which is impossible.

Now I have an example of a socalled co-dominant trait with all the breeding possibilities.

tt = super tiger reticulated python
tn = tiger reticulated python
nn = normal reticulated python

a Breed a super tiger retic to an unrelated normal and all you get is tiger retics.
tt x nn = 100%tn

b Breed a super tiger to a tiger and you get super tigers and tigers.
tt x tn = 50%tt + 50%tn

c Breed a tiger to a normal and you get normals and tigers.
tn x nn = 50%tn + 50%nn

d Breed a tiger to a tiger and you get normals, tigers and super tigers.
tn x tn = 25%tt + 50%tn + 25%nn

This means in a tiger retic, you can see a bit of the normal pattern and a bit of the super tiger pattern. That's why it's called co-dominant. It's possible to say the tiger gene is dominant but then, the normal gene is dominant too and what you see is a little bit of both.