# Hairless vs. Double Rex?



## Finnebon (Jul 15, 2013)

So I'm a bit confused, and I'm sure other people are too since I've seen a few people recently with hairless/double rex babies trying to figure this out too!

It was my understanding that if you have a Double Rex, both parents had to have been rexes or carry the recessive rex genes, hence the "double".

And Hairless is a recessive genetic trait that normal furred rats can carry and if both parents carry the gene, then some of their babies could end up as hairless. (like in the case of Bijou's single hairless baby)

Also "true" hairless being that they have absolutely NO hair at all. No eyelashes, tail fuzz, or even whiskers. But some "hairless" have very very curly whiskers, and some people say that those are actually double-rexes since they have hair. 

But not ALL hairless rats are considered "true" hairless, but just because a "hairless" rat has fur doesn't mean that it's a double-rex either.

Did any of that make sense? Because it's all a bit confusing to me, I was hoping someone who knows about genetics could clarify!


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## Blessed_Yarrow (Aug 17, 2013)

*Re: Hairless Vs Double Rex*

Hello,
I currently have my hairless rat sitting on my shoulder right now! The first hairless rats on the scene were the "true hairlesses". It was a mutation that caused all fur, incuding whiskers and fuzz, to be non-existant. However, several health issues arose from this. Females could not lactate and their immune system was so poor that it was common for them to die within months of birth due to infections or cuts. Behavioral issues such as cannibalism and aggression were also prominent. True hairlesses were actually used in labratories to test immune-boosting medications.

However, rat breeders have worked with breeding Rexes to produce a more sturdy hairless through trial and error. This was by crossing two Rexes with a more favorable hairless gene. The outcome was called a "Double Rex" or a "Patchwork Hairless". They have peach fuzz on their noses, ankles, rump and tails. They also have curly whiskers, a tell-tale sign thet they came from a Rex origin. Their immune system is much better and has the same disposition as regular rats. Females still can't lactate, so breeding hairless rats is a bad idea. She might eat the babies or abandon them. The only way to get a good Patchwork is to breed two Rexes with a good bloodline or purchase one from a good breeder.


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## Blessed_Yarrow (Aug 17, 2013)

Or just to clarify:

*True hairlesses are a purebred mutation

*Double rex or Patchwork is a modified mutation, or hybrid so to speak


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## LuvDaRats (May 26, 2013)

So there's some great questions here but also some wrong information. The differences between a double rex rat (or mock hairless) and a hairless rat and even patchworks is in the genetics. 

Rex is a type of rexoid gene that causes a slow in the hair growth rate which results in shorter hairs than usual as well as it causes the hairs to be thinner and imperfectly formed which gives it that curly look. We know of 7 documented rexoid genes: wavy, rex, ragged, curly1, curly2, kinky and shaggy (though most of these are considered extinct) and there is a proposed veleveteen vareiety though it is still under debate of its genetic uniqueness. Rex (Re) is a dominant mutation and two doses of the rex intensify the mutations effects causing a double rex coat where the coat is rapidly lost in varying degrees. 

Hairless is a all-encompassing term to include the multitude of hairless mutations known and unknown. There are 5 genetically documented hairless mutations: nude (rnu/zrnu), shorn (shn), fuzzy (fz/CRhr). The hairless mutation hairless (hr) is often miss used by many people and is actually the Charles-River fuzzy CRRhr), a allele of fuzzy (fz), and rats do not have this mutation (as seen in mice). There is a theory that what we have mostly in the fancy is the fuzzy (fz) mutation given that this is the one that matches most with what we see and the others are extinct or just not available in the fancy but until genetic testing is done on the hairless we have out there we can't say anything for sure. In all of these documented mutations, all have been noted as having whiskers and usually some degree of fur on the extremities at least some part of their development. From my personal experience with hairless both rescuing, pet owning and breeding, all hairless have whiskers. Patchwork is now considered a type of hairless mutation at this time and often is wrongly used to describe double rex which is completely incorrect on all levels. Patchworks have distinct hair growth and loss patterns and test breedings have shown the mutation to be distinct and independent from rex. 

Just wanted to put a quick note in here about breeding rexes, double rexes, patchworks and hairless. Rex has consistently been a fairly healthy sturdy mutation to work with and double rexes are no different. A lot of people choose to work with double rexes to get their mock hairless because of this. Hairless has health issues tied most directly due to the mutation's nature itself but over the years there have been major improvements to some hairless lines while in the hands of dedicated knowledgeable breeders. We can now have hairless lines that do lactate just fine and seem to be removed from the documented associated health issues noted in science and as seen in early hairless development in the fancy. The biggest issues that Ive seen in hairless has been the shorter lifespans they have and there are theories out there on why. True patchworks seem to have given the most trouble so far and we've seen that some patchwork lines have had debilitating chronic issues with their eyes and its thought that this could be directly tied to the mutation itself instead of a local issue in the line as it hasn't been able to be separated. True patchworks are also pretty rare and hard to get a hold of with no breeders I know of actively working with them at this time.

Hope that helps, this is a somewhat older guide but still got really good info in it to read on coat development-
http://www.ratbehavior.org/CoatTypes.htm#Rex


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## katielove0093 (8 mo ago)

Blessed_Yarrow said:


> *Re: Hairless Vs Double Rex*
> 
> Hello,
> I currently have my hairless rat sitting on my shoulder right now! The first hairless rats on the scene were the "true hairlesses". It was a mutation that caused all fur, incuding whiskers and fuzz, to be non-existant. However, several health issues arose from this. Females could not lactate and their immune system was so poor that it was common for them to die within months of birth due to infections or cuts. Behavioral issues such as cannibalism and aggression were also prominent. True hairlesses were actually used in labratories to test immune-boosting medications.
> ...


Not true they can't lactate mine have been lactating fine they need extra protein. Meat and eggs.


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