Questions about Lethal White

[mrweaw]

Hello,

I have some questions about the lethality of homozygous white.

1. How exactly does the lethality manifest its self?
2. Do the babies die in-utero? Shortly after birth?
3. Does the dam give birth normally or does she have complications with the birth that cause problems for her health?

I have extensive biological training and education and genetics has always held a special fascination for me. I hope you will all forgive me for my morbid curiosity and understand that this is how we learn. Homozygous lethality is an extremely interesting topic and one that I would be interested in researching further. I know that many of you must have experience with this and I am hoping that you will share that information with me. If you do not wish to post graphic details here you are welcome to email me.

Thank you,
Erin

 

[RDZCRanch]

How exactly the lethality manifests is not entirely known. It happens in homozygous TOV and also in homozygous white.

The kits die in utero and are reabsorbed. You will never see or probably even know of the existence of the lethal kits. She won't birth a mummified kit or anything like that.

The dam will still give birth normally to any kits that are not homozygous white or homozygous black velvet. You have to think that after reabsorbing so many kits, this might wear on the mother slightly. There's no benefit in breeding white to white or TOV to TOV.

 

[Brittany]

I've seen this term a lot, but what exactly do you mean by reabsorb?

 

[tunes]

Lots of folks breed TOV to TOV, but it's rare that an experienced breeder will do this with a white. The main reason they won't with a white, isn't so much the loss of the kids or the reabsorption, but because whites already typically don't have the best fur. So putting two whites together is deliberately putting two poorly furred animals together in breeding. To what end? To make more badly furred animals?

Here's a link (if you haven't seen it) that explains the lethal factor nicely: http://www.chins-n-hedgies.com/forums/showthread.php?t=22

As far as reabsorption, it just means that basically the fetus dissolves back into the mom.

 

[Godins Chinchillas]

Forgive me if I am wrong-but I was under the impression that when a white (tov) sperm meets a white (tov) egg that they pretty much say whoa-not going to happen here and nothing becomes of the fertilized egg or zygote...that the zygote gets reabsorbed. Zygote, embryo and a fetus, IMO, are three seperate things.

Correct me if I am wrong.

 

[JennyBug]

I don't view your fascination with the topic as morbid. Just the other week I was looking up the same info. I love genetics (punnet squares ROCK!), and I wanted to understand more.

According to the Silver Falls color calculator, there is a 25% chance of TOV/TOV pairing and a white/white pairing resulting in death of the kit, however, like was said above, you really wouldn't see the effects because of reabsorption.

I'm not a breeder, and I never plan to be, but all of the genetics are amazing!

 

[RDZCRanch]

Forgive me if I am wrong-but I was under the impression that when a white (tov) sperm meets a white (tov) egg that they pretty much say whoa-not going to happen here and nothing becomes of the fertilized egg or zygote...that the zygote gets reabsorbed. Zygote, embryo and a fetus, IMO, are three seperate things.

Correct me if I am wrong.

The thing is that we don't know which stage is occurs at. That's why all three terms are used pretty much interchangeably. I'd assume it happens at the Zygote stage or embryo, but without research no one really know.

 

[tunes]

I've known of several people who have bred white to white and they got all white kits. They were back in the CnQ days. It was pointed out to them that it was seriously not a good thing to do, mainly because of the lack of quality, but they said they would continue to do it because they were "only breeding for pets."

I hate that line. <rolles eyes>

 

[mishalaa]

The only reason we know it's lethal is because of the statistics - 25% less kits overall from such pairings, and no proven homozygous whites or TOVs produced. No one knows when the zygote/embryo/fetus is aborted (most likely early on since it doesn't result in mummified kits), or why.

 

[Mt. Zion Chins]

Way back yonder when I was breeding (13-15 years ago) and there was no information that could be found about chins except in some books. I am ashamed to admit I was breeding pet store chins. I did breed a white to a white. all I out of it was a standard. About a year after my husband found some information about chins on the internet. I was told this was not a good idea so I never did it again. At that time, I learned a few other things that helped me with my breeding program. Unfortunately it was another 5 or so years before I discovered about teeth problems being genetic and that I should not be breeding pet store or 4-h chins. Boy was that an eye opener. For what I understood it meant (lethal) that is just wasn't going to happen (homo. white) and you probably would have less kits born

 

[jags]

I guess I would still like to have it proved to me that anything about it is lethal or that you will have less kits born. All I have ever seen or been able to find on it has been hear say with no documentation or a real study. Now as far as quality from that breeding that's a whole different story.

 

[mrweaw]

Thanks for all the info everybody, I appreciate it. Chinchilla genetics doesn't seem to be as clear cut as it is in other species I have worked with. It really is quite fascinating.
Erin

 

[tunes]

There is a really good book on the MCBA Website, that was written by Alice Klein. You might want to check that out. It's realllly in depth into the genetics of chins.

 

[mrweaw]

I saw it but I haven't ordered it because I wasn't sure if it would be any good. Now that I know it is I will have to do that.
Thanks!

 

[Cuddlebug]

I recently ordered and received a copy of that book. I have read it from cover to cover and learned a lot. I do not regret purchasing it. The title is "Basic Genetics and History of Mutation Chinchillas"