How to Know if it's Pure

[Maxwell Grantly]

Thank you for clarifying that Tad. I appreciate your feedback. (I'll remove the error from my above post - thank you.)

This is a topic that has interested me because, having gained our previous target of obtaining 9T vampire kittens, the next project of Skippy and I was to produce a vampire kitten that was pure in all its nine traits. We decided to inbreed again and again to try and whittle out any stubborn recessive genes and we have been doing this for many generations now. Each generation we would swap out a male, keep producing boxes and wait until we obtain a female and then use her to swap with the parent. Then we would repeat the process. Skippy and I have been doing this many times, swapping males and females alternatively in an attempt to weed out recessive genes by a process of chance.

This is a very long process and one that relies on chance only. However, once a gene is weeded out, it will never return. Interestingly, I was looking through my cattery and saw a page of vampires with all seven cats identical in every trait (Four grandparents, two parents and the cat itself) and so I wondered what the probability was that the cat was pure in (for example) its fur. I was surprised, when I crunched the numbers, to discover that, after all this work, the probability of the cat being homogenous in its fur type was only sixteen out of thirty-two - that was just a half!

Please excuse my rough notes below - the following page was my working out.



(Explanation for above scribbles: Each of the four grandparents are heterogeneous (Aa) and so there is a one in three chance that their offspring are homogenous. (We can discount the "aa" offspring from the maths for we know that the recessive fur is not showing.) When combining these three different combinations for the two parents, 16 homogenous offspring are produced. Again, we can again discount the four "aa" results because we can see from the pedigree page that no cat has a recessive fur type. This means that there are (9*4)-4 different combinations.)

I was surprised to see that, despite having a whole page of identical traits, the final cat only has mathematically a 50-50 chance of being pure in the given trait.

I see that Skippy and I are going to have to continue with this for many many more generations to come!