…..Cats in formation!
Minlit asked a question about white cats and how they come about. The problem is that there isn’t just one answer, there are four different causes to an all white cat.
The first is White Spotting. Spotting itself isn’t rare, but being 100 percent spotted is. A white cat from this cause can have any color eyes. If the eyes are blue, there is a chance that the cat will be deaf.
The second cause is “Dominant White”. This gene will block all color in the hair, and can also result in blue eyes. A blue-eyed cat from this cause can be deaf as well.
The third cause is the True Albino. This is extremely rare, and results in a pink-eyed cat.
The fourth cause is another variant of Albino that results in a pale blue-eyed white cat.
There is one interesting feature of white cats – often as kittens they have marks on the head showing what color they are ‘under the white’. This is handy for breeders who would otherwise not know if a white cat was orange or black genetically.
littlemiao has been working on the Quizlet!
Okay… So, an orange girl-kitten and a tortie kitten would indicate that there must be two fathers, because if there is one orange girl kitten, it means it had to be O/O, but a tortie/calico can only occur with O/o, so that would mean there must be one O-dominant father and one little-o father. Is that right?
And does that mean that different coat lengths in the same litter don’t indicate two fathers?
First off – Great job littlemiao!
Your reasoning is spot on and you have almost all of it, but the two girls must be all black and all orange rather than tortie and orange. In the case you give the orange female does require that both the mother and father contribute an Orange gene. But for the tortie kitten the father could contribute his orange gene again and mom could contribute a non-orange ‘o’ gene if she was herself a tortie cat. The only way to make sure that some other father is involved is to have an all black female kitten – an o/o combination. Since the first kitten was proved to have an Orange dad, the second kitten’s non-Orange dad must be a different cat altogether.
The Orange locus is doubly special in that you can see both genes expressed in a female kitten all the time (due to X inactivation) and you know that the Dad must have had a Y gene that could not be passed to a female kitten. So there are only three genes from both parents that *could* be passed to a girl kitten, so it is logically possible to have an impossible mix with just two kittens.
So trying the same idea with the long hair gene, you have two problems. The first problem is that short hair is dominant. So there is no visible difference between a cat with one gene (L/l) or two (L/L). True dominance thus hides some of the information about the kitten you need to define the parental genes.
So a shorthair kitten tells you only that at least one parent had a shorthair gene, and so was short-haired. A longhair kitten tells you that both parents had a longhair gene, but it doesn’t tell you what they looked like. They could be longhairs (l/l) or shorthairs (L/l). You would need more information to be able to prove anything.
In fact, Julius’ mom was a shorthair and produced a longhair kitten. So we know she was a L/l. We also know Julius’ dad had a l gene, but not if he had two, or one. If you look at the entire litter you can use probability to compute the odds of each parent gene option, but you can’t know for sure.
The final problem with the longhair gene is that both parents have two genes to contribute to any kitten. So you need more than two kittens even in theory to prove a third parent’s involvement, or you need more information about the parents. For a trivial example, a single shorthair kitten requires a second father if you know both parents were themselves longhairs – ignoring a spontaneous mutation.
All good things must come to an end!