Help with Double Recessive Punnett Square Coding

[Bundu Boy]

Hey All

I've been getting my head round the use of the Punnett Square and have typically got the dom/co-dom and single recessive breeding understood.

My question comes now to Dbl Recessive breeding , in particular the codes used to denominate double hets.

I'll use the example of breeding for a Snow (Albino x Axanthic)

Albino = aa
Axanthic = xx

Breeding these together (aa x xx) would give me 4 x ax.

Now these should all be normal looking babies but all are carrying the recessive gene for Albino and Axanthic, a double het.

Would I be correct in portraying a dbl het albino/axanthic as AaXx for use in a punnet square?

If so, then would I receive the following theoretical results from breeding a pair of dbl het Albino/Axanthic?

AAXX Normal x 1
AAXx Normal Het Axanthic x 2
AaXX Normal Het Albino x 2
AaXx Dbl Het Axanthic/Albino x 4
AAxx Axanthic x 1
Aaxx Axanthic Het Albino x 2
aaXX Albino x 1
aaXx Albino Het Axanthic x 2
aaxx Snow x 1

Thanks!!

[bc30629]

http://www.geckosetc.com/htm/double_recessive.htm

Just found that with my good friend google. That should help a bit.

[roosterman2173]

[Bundu Boy]

Cool bananas

That site confirms what I thought, thanks bc30629.

Rooster - ??

[dcgator24]

I use N for the normal gene. Little less confusing without all the A's and X's.

Dbl Het - NaNx

[muddoc]

I use N for the normal gene. Little less confusing without all the A's and X's.

Dbl Het - NaNx

The problem with that is now you are representing three genes in your coding. N, A and X. That is actually totally confusing, unless you want to draw a 16 x 16 square representing triple Hets.

[dcgator24]

No there wouldn't be three genes in the coding. I just don't like using large and small a's and x's. Instead of using large letters to designate normal genes, I use N for both a and x. The punnet square is the same 4x4 16 combination square. You don't need to use different designations for the normal gene, ie A and X. N works the same for both of them. To me it's much simpler to read. The 4 possible combinations that build the punnet square are Na Nx ax and NN. The resulting possible offspring:
6% aaNN - albino
6% xxNN - axanthic
6% xxaa - snow
12% aaNx - albino het axanthic
12% xxNa - axanthic het albino
25% NaNx - dbl het
12% NaNN - het albino
12% NxNN - het axanthic
6% NNNN - normal

When I'm filling out the punnet square and I get a NN I just drop it because it's not necessary. But I leave it here for better explanation.

[stangs13]

That is actually totally confusing, unless you want to draw a 16 x 16 square representing triple Hets.

I did thoughs in ag class, I totally owned!!!

[RandyRemington]

It looks like maybe you are using position to keep track of which N is which. Of course the normal for axanthic gene is completely different than the normal for albino gene. It looks like maybe you are using position to keep track of which N is which. Of course the normal for axanthic gene is completely different than the normal for albino gene. I like the capital and lower case versions of the same letter to show the relationship between the normal and mutant version of the same gene but of course it can be a little tricky remembering which is the mutant. And with the white snake complex where there are more than two versions I’ve started using subscripts.

[dcgator24]

There's no need to know which normal it is. It's still normal, no matter what recessive genes you're working with. If an offspring happens to get normal for albino but the mutant axanthic, it doesn't matter because it's a normal phenotpye and won't show to carry the axanthic gene until proven. It doesn't matter that it got the normal albino allele. It has no effect on the genotype or phenotype. It would be the same for any punnet square combo. NNNa is still het for albino regardless of what axanthic allele it received. NNax is still double het. It doesn't matter what postion the N is in. NaxN aNxN axNN its all the same. aaNN is the albino genotype, as well as aNaN, NNaa. You wouldn't call it albino normal for axanthic.

The way I do my punnet squares is just the way I do it. You get the same results using uppercase and lowercase recessives. I just think it's much easier to read without all the upper and lowercase letters. For example, if a person new to genetics or punnet squares gets a punnet combo of AaAa it may be difficult for them to decipher what that is. H aaNN seems easier to read and understand, especially when you don't have a lot of other uppercase A's and X's all over the punnet square.

I do the same for codoms. Either the mutant allele is passed or the normal. N is the normal. It should work for the white snake complex just as easily. No need for subscripts. A lesser/mojave bel would be simply LM. It's correct that a bel cross only passes one of the mutant alleles right? Not both? Either lesser or mojave? And no normals? When bred to a lesser the columns are L M rows L N. Offpring:
25% LL - lesser/lesser bel
25% LM - lesser/mojave bel
25% LN - lesser
25% MN - mojave