If you pair two 100% het gliders together and the joey comes out grey, it would be 66% het right?

But what if one of the adults was 100% leu het and the other was 100% platinum het. Would the joey be 66% leu or plat? They're both recessive genes that somehow work together, just unsure as to the het of the joey.

Two 100% het gliders each have 1 gene for the recessive trait. The grey joey they produce would be called a 66% het because it COULD have received 1 copy of the recessive gene from either parent. If you think of the pundit square - each parent is carries one dominant and one recessive gene (Aa). There are 4 possible combinations of these genes in their joeys 25% would get Both dominant genes = AA grey 25% would get both recessive = aa (and show the trait) 50% would get a dominant gene from one parent and a recessive from the other = Aa grey. If you base the percentage off the 75% of the joeys that would appear to be grey gliders - the 2 of the 3 possible combinations producing grey gliders would actually carry the gene - giving the 66% CHANCE that the grey joey carries the gene. Technically - I believe the percentages are misleading -unless you are a gambler - in reality it should be 50% - it either carries the gene or it does not.

I am not sure how the leu and plat genes work together.

Thanks, I understand that. But with two recessive genes I was wondering more whether a grey joey would be 66% het for Leu or 66% het for Plat. That's where my confusion is.

If you use the same Punnett square calculations (Parents: Gp and Gl, Potential offspring: GG, Gp, Gl, or pl*), then grey-colored offspring should be considered 33% leu AND 33% plat het. (Could alternately be called 66% leu OR plat het).

*The "pl" offspring should be platinum in phenotype. (The platinum allele provides just a hint of grey while the leu allele provides none, thereby creating a light colored glider.)

That said, I agree with Candy; either your joey has the allele or not, and it makes more sense to me to just use 50%. Statistics are too easily manipulated to really be of use in this situation, and to be honest, even biologists prefer to avoid het percentages in publications because it creates controversy. In real life (as opposed to the "math" world) I would just advertise the joey as a leu/plat het and direct any potential parents to the pedigree and let them figure it out themselves. :)