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Hi! I bought a female from a petstore that was already pregnant of course... I wouldn't dream about taking on a litter otherwise. I just have a genetics question I am hoping to tackle with you guys. I am only asking because this is the only chance I have at trying my hand at guessing genetics and stuff due to this litter, so it will be interesting. xD

So my female is a black hooded dumbo rex rat with an unknown father. I had 9 babies in the litter and these are the outcome. The litter is 4 weeks and 5 days old now.

Fur Type:
1 Smooth/Regular Fur
6 Rex
2 Double-Rex/Patchwork

All babies are dumbo eared. That means that the father has to be a dumbo rex for sure, right? Since I got hairless and dumbo babies and they are all recessive? And since I got one normal haired baby, both the parents have to be Rere, so one rex gene and one normal haired gene? What could be the coloration of the unknown father?

And again, the litter is 4 weeks and 5 days now, so will other babies have a chance to lose their fur to become a patchwork/hairless? Or is all the hair stuff set right now.

And the last important question. My critter nation double for the guys came in tonight. The females were already in a critter nation double. Can I just "cold turkey" separate the males from the mom right now? Or is there a process I need to do? Thank you so much for answering!

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Yes I would separate the boys. They should be separated from their mom/sisters by 5 weeks old.

I dont work with rex myself but yes the dad was dumbo if all babies are. & I believe would be rex too.
Interesting read on rex http://www.afrma.org/rexrat.htm

It is really not that easy to guess a rats genetics based off phenotype always.

You do not need to put it in practice to learn about genetics. There is alot of info online you can read about.

http://www.afrma.org/ratgenpart1.htm
http://www.ratbehavior.org/CoatTypes.htm
http://www.raffinhouse.com/basic_genetics.htm
http://www.afrma.org/ratgenwhatif.htm
http://rainydayrats.8k.com/custom4.html
http://rat-breeder-confessions.blogspot.com/2015/12/genetics-starter.html
 

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It does, indeed, sound like the father was also a single rex. If you consider both parents having Rere (where Rere is rex and rere is standard), then a cross between them should, in theory, yield 1/4 ReRe (your double rex pups), 1/4 rere (the standard pup), and 1/2 Rere (the single rex pups). The math doesn't always work out obviously, but this is the only cross I can think of that would give you those three coat types within the same litter. I did some work with rex rats previously, it's probably one of my favorite genes in rats.

Just as a side note since abbreviations for coat types can be deceiving: re is not a recessive version of the rex gene but rather the easiest way of showing that they can still pass the standard coat gene (which is also dominant, but less dominant than rex). Since Rex is dominant, if a rat has it, it will show. There are likely other genes that influence the quality of the fur in rex rats, but that's more advanced than most people get in to lol
 

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I agree dad was a dumbo rex, (Rere dudu) however its hard to tell if he was black, or another self-colour that mum doesn’t carry (Self being recessive means that he’s highly unlikely to be an agouti based rat). He’s also likely to be marked, probably a black hooded or Berkshire rat but that’s a guess.

In terms of separating males I tend to split mum off both sexes when the time comes, usually because she’s a bit chubby from all the babies food, or the babies are, plus she’s keen to get some adult company back with her group. If your mum is on her own then I guess she will be staying with the girls. I tend to do a gradual separation, so over week 4 I will get mum to spend more and more times away from the babies (and back with her original group) until she’s actually spending a good 4 or 5 hours some days away from them. Then when its time to split them I pop her back in with each group for a couple of hours a day just to settle them for the first few days ( I tend to move her in first with the rats moving to a new cage, or sometimes move the whole group into the new cage first to make it smell safe for the boys). At around 5.5 weeks theres no more contact. To be fair my lot mature fairly late but theres not much risk of a 5 week old buck actually managing to successfully mate an adult doe so whilst I’m sure mine aren’t fertile at that age I wouldn’t worry too much even with faster developing lines, the bigger risk is the sisters.
 
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