genetics

Question
okay so i have bred my nlue satin rex male to my siamese fmeale and i would like to better the curls do i just breed a baby back to the father ? or do you have any other ways to get better curls?

Answer
Hi Dustin,

I am assuming that you have already raised the offspring and they turned out to have curly coats - this means your dad and offspring mice most likely have the dominant gene Re (astrex) causing their curls.  This is important because the other genes that can cause curly coats, such as fuzzy, are recessive and would not have shown in the first generation with a non-curly carrying mom (because the offspring would inherit one recessive curly that wouldn't show, and one normal coat that would).

Now that you know which kind of gene is causing the curls, we can figure out how to improve them.  Astrex mice DO show better and longer lasting curls when homozygous (one copy of Re from each parent), so yes, breeding back to the father when an offspring doe is old enough would help the coat of her pups.  To understand the results, though, is a little bit more genetics:

Since the mom of the next generation will have one rex gene and one normal one (rex from dad, normal from her mother), and the dad will also have at least one rex gene (since he is curly-haired), your possible offspring of the dad to the daughter will theoretically be either...

1.  75% curly (25% Rex/Rex, 50% Rex/normal), and 25% normal
So about one fourth of them would have the improved coats, half would look like mom, and one fourth like grandma siamese.  This is the case if dad has one Rex gene and one normal gene.  This is great news for improving the coat, because you may end up with a fourth of the offspring looking even better than dad, so you can continue to breed until you have all Rex/Rex mice with great, curly coats.

2.  100% curly (50% Rex/Rex, 50% Rex/normal)
So about half would have the improved coats, and half would look just like their mom.  This is the case if their dad has two Rex genes.  Since the offspring will look like dad, because both offspring and dad will have two Rex genes - that's all the improvement they will be able to manage - further breeding won't be very useful in making the coat curlier, unless you are improving other genes incidentally.

Other than the outcomes I just described, there are no other ways I can help with that improve the curls.  There is always a little more to genetics than we know of, though, so I definitely suggest striving for better and better coats.  The best reason to breed is to improve the mice!  There are almost certainly factors in the expression of the curls that we just didn't know affected them yet, so by picking out the best coats and breeding those, and with a solid understanding of the genetics behind them, you should certainly see an improvement over time in the coats and how long the curls last!  Remember though that breeding back to the dad may lose your siamese genes in the mix a bit unless he is already a siamese mouse as well, so it may take some puzzling out.

Best of luck and I hope I helped - please ask if you have any questions or if I wasn't clear in anything.  Also, here are some great links on rex genetics to help out:

http://www.hiiret.fi/eng/breeding/genetics/coat.html - coat genetics

http://www.fancymicebreeders.com/phpBB3/viewtopic.php?f=26&t=2403 - rex and fuzzy explained

-Tam