Lethal Genes- bring on the experts!

[Vyxxin]

Okay, I know a LOT about chin genetics...and I don't generally dabble in things that I'm not 100% sure of...but I wanted to throw this out there. As a disclaimer, this thread is in no way shape or form an excuse to breed for the sake of breeding, to breed poor quality animals, to breed carelessly, or to breed without good sound knowledge on the subject of breeding.

That said, for the 8yrs I've been in the "business" of chinchillas I STILL have no sound understanding of lethals. I get which phenotypes/genotypes they occur in, I do really...this is more a question of "when did the old timers discover this" "how was it proven" "are we sure it exists" "in two perfectly healthy, quality chinchillas, is it detrimental to their health or that of their offspring" That type of thing. Obviously I have no intent of pairing said lethal combos...as I breed darn near everything that isn't gray back to a gray...but it's been too many years since I read Alice Kline and the like and my knowledge on lethals has gotten a bit fuzzy anyone better versed on the matter care to chime in?

 

[mark miller]

I have never fully underestood the lethal gene either, however I have mated black velvet to black velvet and never visually saw any problems with offspring. Had many nice black velvet and standard babies including a GSC black velvet male that was an exceptional producer. I've never bred white to white because they're is no real benefit of doing so. Whites tend to lack fur strength and overall fur quality and need to be bred with something of better fur quality to improve. I have bred strong furred pink whites to whites and again never visually observed any differences in offspring, litter sizes, complications, reproduction, nothing out of the ordinary. Now it is possible that if those lethal gene fetuses resorb then there would be no physical signs but maybe smaller litter sizes. I did not notice any difference in my breedings and had several triplets, once recently I had 2 whites and a pink white born to a white mother and pink white father all perfectly healthy. From my experience the "lethal gene" is not a factor to worry about. But, I do not breed these combinations unless there is a beneficial reason for quality. Black velvet to black velvet can be done to set in the velvety texture that black velvets generally have. The white girl that I bred was very white but lacked fur strength so I used her with the pink white male that had strong, tight fur from the beige genes to improve offspring. If there is no quality reason to do these type of matings I wouldn't do it. These are my findings based on my experiences in breeding these combinations.

 

[Spoof]

I don't mess with Tov to Tov because I work with it when it is attached to a white animal.

With the whites - before I owned chinchillas I knew someone that had them. She had three white females, one a Tov pinkwhite. They were in with a standard and produced a couple of nice litters. Then she traded for a Tov pinkwhite male that someone else had been using for breeding that threw a lot of kits. She put him in the trio. Three years later all three females had dead with only two kits to show for it - one BV and one Tov Pinkwhite F (which was my third chin). I know there are different strains of white, and likely that one had some sort of issue. Regardless of why they died, it steered me clear of breeding white to white.

Like Mark said, nowadays there is no point in breeding white to white due to the qualities more than anything.

Ronda has Alice Kline's book sitting here, but I don't see anything about mutations.

 

[Vyxxin]

Anyone know where the current theory and statistics on the lethal gene arose? I would never really conside whitexwhite but was actually asking (mostly) for the bvxbv aspect. Just the same, really not planning on doing it, more a curiosity towards where the current "info" on the matter came from

 

[Spoof]

Bob Gunning and the Colbys produced the current theories. To create the veiling they bred veiled sooty faced animals to the same sooty faced line. As they became more veiled they had a tendency towards being Brevi and slow breeders.

The consensus to the people standing over my shoulder here is that they simply produce less babies, and they have a tendency to die after birth. Gunning did, and it's just slow going.

 

[KissThis]

I am not totally sure on the history of the BV and white mutations as far as "proving" that they are lethals. They are both considered embryonic lethals, so you would not see a difference in the live kits produced. You may see a difference in the number of kits produced and possible complications arising from incomplete re-absorption. One of the biggest proofs that these two genes are homozygous lethals is that there are no homozygous Black Velvts or Whites out there. Meaning that there are no Black Velvets or Whites that have more than 50 kits that have produced either 100% Black Velvet kits or White kits when mated to standards. Given the number of times these colors have likely been crossed, either during their development or by those that don't know about the genetics, if the homozygous state was viable for either of these colors we would have seen homozygous animals in both of these colors. Also as far as genes go there is no mixing of genes, so it doesn't matter what other colors are expressed with the white or the black velvet, those genes still pass the same as an animal that only expresses white or black velvet. Meaning that breeding a white to a pink white is still a white to white cross. Hopefully this makes sense.

 

[RDZCRanch]

The theories came about because of the same lethal effect in rabbits. Rabbits have been studied extensively and the lethality of certain genes occurs for them inside the womb during embryonic development. Since the two species are fairly close in relation, we assume the lethal genes in chinchillas work the same way as rabbits.

Like Cara said, if there was not a lethal gene present for the TOV gene and the white gene, we would have found a homozygous of one or the other by now. I know plenty of ranchers that tried black to black to produce a homozygous TOV and none of them ever achieved it.

Mark, a pink white to a white is still a white to a white. The beige gene being present does not negate the lethality of the white gene in its homozygous state. You would not notice any problems with the kits that are actually born since the lethal genes in chinchillas is an embryonic lethal (as Cara mentioned) meaning the fetus/embryo dies in the womb and is reabsorbed. The only thing that should be noticeable is a smaller amount of babies produced which may or may not occur depending on random assortment from the parents genetics (whether or not the embryo is homozygous white or homozygous TOV, which would be a 25% chance for each embryo).

 

[Vyxxin]

Well...I see the logic, but wish there were more facts or stats for this. It stands to reason that years and years of "lethal propaganda" would cause a VERY small portion of breeders to actually attempt such crosses. Out of that small portion, and their small number of lethal pairings (I know even if I were to try it, it'd be on a super small scale), only 25% would even have the opportunity of being homozygous. AND out of that 25% how many do you think were bred conclusively?

I'm just saying, it's something to ponder. I like hard facts, and in this aspect of chinchilla breeding there does not seem to be a whole lot.

ETA- might be a bit of a conspiracy theory...but back in the day chins cost a LOT more...if I were a breeder with a homo black or white...well, I wouldn't admit to it and would furthermore propogate "lethal genes" theories

 

[Vyxxin]

Something else that's been on my mind, because I'm no genetics expert...but didn't most of the common coat colors (bv, white, beige...) arrive from two gray parents? Wouldn't this almost be like a recessive trait? (serious question, not an expert here) Likewise, look at ebony/charcoal...one dominant...one recessive...crossed and mingled and now? I'm just saying, is it not possible that other existing mutations (such as the bv,white, beige etc) have recessive forms? And if so, how many breeders (or byb) would realize it if it cropped up?

ALSO, sorry I'm rambling...just really interested in this subject...out of the small number of people pairing lethals, and the even smaller number of lethal pairings they have paired up...only 25% of those resultant offspring could be homo...and out of THOSE...only the males would be worth "testing" for homo because it'd take too long for a female to produce sufficient offspring to PROVE homo genes...so just 12.5% of all offspring from the limited lethal pairings would even be worth testing...

 

[minrex]

The theories came about because of the same lethal effect in rabbits. Rabbits have been studied extensively and the lethality of certain genes occurs for them inside the womb during embryonic development. Since the two species are fairly close in relation, we assume the lethal genes in chinchillas work the same way as rabbits.

Rabbits aren't particularly closely related to chinchillas at all. They're in a completely different taxonomic order (Lagomorpha for rabbits, versus Rodentia for chinchillas). Anyway, I can't think of a coat color in rabbits that is considered lethal. The dwarf gene in rabbits is lethal, but does not typically cause embryonic death. Are you sure you're not thinking of guinea pigs, which are closely related to chins and do have lethal coat color genes?

To the OP: if you're dealing with a heterozygous animal, you USUALLY won't have to see very many offspring of that animal in order to see that it is heterozygous. For example, if you have a heterozygous TOV chin in breeding (bred to non-TOV animals), the odds of that TOV chin's first 10 babies all being TOV are extremely small (less than 0.1% chance). As soon as a TOV (or white) chin has a baby that is NOT TOV (or white), that animal is known to definitely be heterozygous. When colors like TOV and white first came on the scene, you can bet that people bred TOVs to TOVs and whites to whites. Over the course of a few dozen litters, it may not have been apparent that litter sizes were smaller with these pairings, but over the course of hundreds of breedings, the numbers would show that TOV to TOV or white to white pairings were producing about 25% fewer kits, if the lethal gene "theory" is true. Considering that some ranches had thousands of animals, and that many ranchers kept complete records of the number of kits they had from various pairings, I don't find it dubious that this discrepancy in litter sizes was noticed. It would also have been fairly easy to see if a TOV animal was heterozygous by looking at its kits. As I said, it doesn't take too many offspring to see whether the parent(s) is/are heterozygous. Of course it's not impossible for a heterozygous TOV animal to produce 100% TOV babies, but it's highly unlikely if more than a handful of offspring are produced from that animal.

I also don't quite get your claim that since only 25% of kits from TOVxTOV matings would be homozygous, that they would be rare and few would be bred. Look at beige to beige breedings; only 25% of kits from two beige parents are homozygous beige, but homo beiges aren't extremely rare. Neither are violets (or non-violet-carrier standards, for that matter) which were produced from two standard vc parents. If TOV was not lethal in its homozygous form, you absolutely would be able to find homozygous TOVs which had never produced non-TOV offspring from several litters.

I don't know that anyone can convince you if you're determined to believe that TOV and/or white might not be lethal. In my opinion though, the evidence overwhelmingly indicates that they are.

 

[GorillaJTA]

Lethal factors exist in most (if not all) species. Most of them are just not studied as easily as those of highly bred animals like mice and chinchillas.
There is a lethal factor for yellow coat color and for a form of white coat color in mice. The lethal factor in the yellow mice is attributed to mutation in the yellow coat gene which adds a section resembling a necessary RNA binding gene which is normally present, and with a homozygous embryo is not expressed, causing the embryo to be inviable. Basically- a mutation in the gene messes up the expression of a necessary protein which makes the developing embryo inviable and causing it to be reabsorbed.
The same thing happens with the white coat except it causes a type of anemia rather than a RNA binding protein deficiency. Homozygotes of short-tailed house mice also have a lethal factor for neural developmental problems.

Humans even have lethal factors, but with the long gestation, long implantation time, and rarity of multiple births, most of them are reabsorbed before pregnancy is recognized.

In the chinchilla, while the physiologic effect of the Bv x Bv or W x W has not been determined, it is probably something along those lines- a mutation that caused a coding error which in a heterozygote is accomodated for by a wild-type (healthy) gene.

Because of the limited initial breeding population of chinchillas, the potential for mutations is exponentially higher than if wild animals were consistently brought in to improve the breeding pool. Even now, with the wild population of chinchillas extremely low, the influx of new animals may not alleviate all the problems of the original mating pool.

 

[Vyxxin]

Well, first of all...I'm not a know it all (hence the point of the thread) second of all...I'm not new to chins nor am I trying to justify any of my theories. I'm looking for sound evidence from the theories of OTHERS

And your examples of other homozygous animals it moot because it is evident (by coat color) when a homozygous is produced and much easier tested. Since we have no idea what a homo black or homo white would look like phenotypically...

Furthermore, while the old timers may've kept great records...do we personally have access to those? (seriously, do we?) I'd be more apt to take note of records produced by an entity that does NOT have a vested interest as the pelt/chin producers of the past surely woud've had. That be the case, I'd still love to see any records at all that indicate a lethal...again, hence the point of the thread

This thread is based on hypotheticals...and is meant to be somewhat informative as well...this is how knowledge is gained, information sharing.

Finally, I've recently done some investigation into the coat colors of other species (such as mink) and have noted that many other species have many many more mutation colors as well as many more recessive colors.

ETA- thanks for the info Gorilla, and I DO know it's accurate that most species DO have lethal genes. Was simply pondering the possibility that perhaps not all strains of whites or blacks do and what the repercussions of that would be. Likewise, any input on the homo/hetero/recessive influences there were when the mutations originally cropped up? I know this involves indepth genetic terminology but if someone could "dumb it down" so I can understand how the orignal mutes (which came from two gray parents) were dominant and not recessive as that would indicate?

 

[RDZCRanch]

Rabbits aren't particularly closely related to chinchillas at all. They're in a completely different taxonomic order (Lagomorpha for rabbits, versus Rodentia for chinchillas). Anyway, I can't think of a coat color in rabbits that is considered lethal. The dwarf gene in rabbits is lethal, but does not typically cause embryonic death. Are you sure you're not thinking of guinea pigs, which are closely related to chins and do have lethal coat color genes?

It may have been guinea pigs, but the rancher that told me about where the theories came from said rabbits. I couldn't think of a rabbit coat color that was lethal either. Even though they are in different orders, they are still fairly closely related.

Vyxxin, I don't think you are understanding what a coat color change in chinchillas is. We have dominant and recessive genes for changing the coat color which has been proven time and again with the various colors that are available to the public now. These colors appeared not because two standard parents carried genes for these colors, they occurred because of random mutations along the genetic sequence for coat color. During DNA synthesis, mistakes can be made and overlooked, resulting in a mutation that presents itself physically. This is why we call our colored chinchillas "mutations" because they occurred from mutations.

MANY ranchers is not a "few" breeders. With the amount of money Bob could make from a homozygous TOV producing TOV consistently for him, you bet your butt he tried for a long time to get one. You have to remember that he worked with this mutation quietly behind closed doors for a LONG time before releasing them to the public. He said he tried TOV to TOV over and over again and stopped doing it when he couldn't produce a homozygous TOV and was having slower production with TOV to TOV pairings. A homozygous TOV or white would by no means be "rare" and therefore less likely to appear because of a 25% chance. A 6.25% chance is low, but a 25% chance is fairly normal. You have to remember that two violet carriers paired have the same probability of throwing a violet (homozygous recessive) and two beige paired have the same probability of throwing a homozygous beige (as minrex mentioned). Also, females can prove themselves heterozygous faster than the males if they have larger litter sizes and they take up less space and mates for "testing" so I think ranchers would be MORE likely to use the females than the males. It would be great to test males, but ranchers don't put males with more than three females unless they are super producers or super quality males.

I am not understanding these genetics "debates" lately where everyone is questioning the way chinchilla genetics works. Genetics is a field that has been studied extensively and can be applied to ALL living things (plants AND animals...even prokaryotes). I suggest if anyone wants to understand genetics more extensively that they take an upper division college course on basic genetics.

 

[GorillaJTA]

Finally, I've recently done some investigation into the coat colors of other species (such as mink) and have noted that many other species have many many more mutation colors as well as many more recessive colors.

Lots of the coat shades in other animals (where shades would be more accurate than mutations because of incomplete dominance and multiple copies of certain genes) can be attributed to pheomelanin which produces red pigments which chinchillas lack in any recognizable amount.

 

[chechinchillas]

This thread is very interesting and much of it way over my head. I recently purchased a black velvet from Somavia and when I received his pedigree I emailed Vin because I thought there was a mistake since it showed both the sire and the dam being black velvets. They said that the pedigree was correct. He is just now in breeding with a huge standard. The only other time I have heard anything about breeding black to black was when Shoots said he did do that once and the baby was born without genitals. I have also been told that black velvets or any TOV are more prone to malo since they tend to resemble the brevi head type. Have you heard of any evidence proving this?

 

[lsknc]

i know a breeder that has been breeding a tov white male with a brown velvet female. she has had several litters with this pairing. mostly just beiges, from my understanding, but she recently just had her first white male born from this pairing.

 

[Vyxxin]

Vyxxin, I don't think you are understanding what a coat color change in chinchillas is. These colors appeared not because two standard parents carried genes for these colors, they occurred because of random mutations along the genetic sequence for coat color.

Actually, I DID know about that Just forgot, as I said in my OP...it's been a few years since reading on the matter

MANY ranchers is not a "few" breeders. With the amount of money Bob could make from a homozygous TOV producing TOV consistently for him, you bet your butt he tried for a long time to get one. You have to remember that he worked with this mutation quietly behind closed doors for a LONG time

Well, even many ranchers...have you seen their records? Do you know much about politics? And you're right, that kind of animal WOULD be worth something...probably not worth selling...more worth keeping...all I'm saying is that there are a LOT of politics in any animal husbandry. The stuff that "goes on behind closed doors" isn't always outed, like malo rampant in herds or new mutations. Probably more conspiracy theory than anything, but it's possible. I'm just wanting some facts...some stats...wasn't trying to argue anything here. Just point out what hasn't been outwardly proven.

A homozygous TOV or white would by no means be "rare" and therefore less likely to appear because of a 25% chance. A 6.25% chance is low, but a 25% chance is fairly normal. You have to remember that two violet carriers paired have the same probability of throwing a violet (homozygous recessive) and two beige paired have the same probability of throwing a homozygous beige (as minrex mentioned). Also, females can prove themselves heterozygous faster than the males if they have larger litter sizes and they take up less space and mates for "testing" so I think ranchers would be MORE likely to use the females than the males. It would be great to test males, but ranchers don't put males with more than three females unless they are super producers or super quality males.

I don't recall (without re-reading all my words) saying rare to anything. Simply that if one WERE produced out of the 25% that we'd have to test a LOT of offspring (like all of it) as we wouldn't really know what a homo black or homo white LOOKS like phenotypically. Also, I'm still pretty sure most ranches spend more money on good males...and likewise are more concerned about the quality of males (versus females) because males propogate their genes quicker. One female with good littering capabilities...still isn't as good as 3 with the same good littering capabilities...or 4 or 5 (which a LOT of ranchers/breeders have their males with that many females)

I am not understanding these genetics "debates" lately where everyone is questioning the way chinchilla genetics works. Genetics is a field that has been studied extensively and can be applied to ALL living things (plants AND animals...even prokaryotes). I suggest if anyone wants to understand genetics more extensively that they take an upper division college course on basic genetics.

Right, because asking a genetics question on a forum...where there are people that KNOW this kind of stuff...and can explain it isn't adviseable anymore. I thought this was a place to share info? You can't get a question answered if you never ask...sort of narrow minded.


ETA- Gorilla, I'm on board with that...I knew that it's more shades of colors than actual mutations live pretty locally (and have visited) a mink ranch that has sapphires and blue iris...comparable to how sapphires, s/c, and gray chins look

 

[mishalaa]

What's the point of wanting to see records/stats if you would just think the rancher could have falsified them to preserve a secret homo black/white animal? That's the problem with conspiracy theories, you're never going to get a satisfying answer. The homo beige was not kept a secret, I can't think of why a homo black or white would be.

 

[RDZCRanch]

Right, because asking a genetics question on a forum...where there are people that KNOW this kind of stuff...and can explain it isn't adviseable anymore. I thought this was a place to share info? You can't get a question answered if you never ask...sort of narrow minded.

Asking questions that have simple answers is fine, but to me, when it comes to something more complex and convoluted like genetics it's best if you have a small amount of basic genetics background to follow the answers.

There are plenty of politics involved in chinchillas, but there is also plenty of gossip. If anyone was able to produce a homozygous TOV or homozygous white we would have heard of it by now. I've noticed that while ranchers can be secretive, they also like to brag and in my opinion, if they had a homo TOV or homo white...the bragging would be unbearable. The things most likely to be kept quiet behind closed doors are malo, health issues or things that would give the rancher a BAD reputation.

The reason we don't have "hard facts" for chinchillas is simply because no one is willing to invest the money in the research. Ranchers invested in a few studies way back when, but I have no way to access that information other than by word of mouth from the ranchers. But, as far as genetics is concerned, we have enough hard facts from other animals that have a similar pattern of inheritance that we can conclusively follow a good amount of chinchilla genetics without fully mapping out the chinchilla genome.

 

[Spoof]

Before asking about the lethality of the Tov mutation you need to understand the mutation itself. It is an accumulative mutation. It was started with a black dirty faced animal.

It stands to reason that years and years of "lethal propaganda" would cause a VERY small portion of breeders to actually attempt such crosses.

Very much not true. At $5,000 per animal you bet your butt everyone bred black to black to standard to whatever to produce as many as they could. And not on a small scale, the Colbys had 6500 cages in their barn when we went up there.

while the old timers may've kept great records...do we personally have access to those? (seriously, do we?)

Yes. I had two standing behind me for the last post (who admittedly don't know how to use the internet) yakking up a storm about ooooo don't do that! They knew Bob, they knew the Colbys (Bob's partners - the blacks were split between the two ranches) and they've been in the business and have a few original black lines. You just have to ask. Blacks are extremely slow to breed together. The kits randomly die before a year of age and they're "trouble".

Granted this is the old genetics they're talking about - even Bob himself said he couldn't have imagined what the black would look like today. He was floored at the last show he attended. The original blacks had a different style and fur type. It was very short and velvety. Today's animals are mooses that have long dense silky fur. They really have changed a great deal in the last 10-20 years.

Wish Bob was still around to ask, he loved to yak chins.