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#69724 - 11/22/05 08:06 PM Color Genetics-leucistics and grays to start with!
Anonymous
Unregistered


Okay, I'd like to get the ball rolling here on a color genetics discussion. I will post what the gene for leucistic acts like, and anyone who can refute it, please do, and hopefully anyone who doesn't know a whole lot about genetics will have a better understanding of how leucistics come about when a breeder uses heterozygotes in his/her breeding program. I would love it if anyone could please enlighten me (and everyone else who is in the dark) on how the other color genes (buttercreme, white face blond (which seems like a recessive gene?), cinammon, lion, and platinum)
work. This discussion isn't meant for the pattern genes and mutations such as calico and mosaic, since those sound a bit more complicated and less likely to follow simple
dominant/recessive rules. If anyone knows of colors that are polygenic, that'd be great if you'd share how those colors work! Also, someone please explain the differences between albino and leucistic genetics! In a lot of species, albino is dominant; is it in sugar gliders as well?
Please try to use the format I'm using for easy reading if you are going to explain a color gene.

If the gene for leucistic is a recessive gene, then these rules should hold true. I'll tell you what you should get in each breeding, and show my work afterwards. Those of you who are breeders or are very familiar with genetics will already know this info. This is for those who are wondering what 66% het for leu might mean, and what chance you might have of obtaining a leucistic when breeding heterozygotes.

Note: When refering to color genes and explaining the genetic terms, I am only speaking of the interaction between standard gray gliders and leucistics. I know that
other colored gliders besides gray can also carry leucistic (such as buttercremes and white faced blondes) but in this post I'm only speaking of standard grays and leucistics.
If you are adding to this post, please do talk about the interactions between the various other colors, as this is exactly what I am hoping for!



A Few Definitions: (these are my own definitions to make reading this easier for anyone who is less familiar with Punnett Squares, etc. They are not necessarily from any textbook and I'd like to make a disclaimer that they may not be 100% perfect.

Dominant: A gene such as the standard gray, which will mask a recessive gene any time there is a dominant gene present. That is why a glider can carry the gene for leucistic but look like a standard. The only why to tell for sure if a glider is truly heterozygous for leucistic would be to test its DNA (expensive) or to breed it to know carriers and see if any leucistics crop up. The exception to this is when a leucistic is bred to a homozygous standard, in which case 100% of the time, all offspring will be heterozygous for leucistic.

Recessive: A gene such as leucistic that can only show itself if a dominant gene is not present. This is why leucistic gliders do not carry the gene for standard and cannot have standard offspring if both parents are true leusistics.

Homozygous: Leucistic is homozygous because it has 2 recessive genes, making the glider white. Some standards (without any leucistic in their ancestry) are homozygous for the standard gray color. To test this, you could take a standard gray and breed it many times with leucistic gliders. If none of the offspring are leucistic, then you have a homozygous standard gray. (But who would do that when people aren't trying for heterozygotes, they're trying for leucistics!)

Heterozygous: These are those marvelous gliders who are hiding special colors behind their standard gray appearance. When bred to a leucistic or to another heterozygote, they can produce leucistics. A heterozygote shows the dominant color but carries the recessive color. A heterozygous gray can only have leucistic offspring if it is bred to another heterozygote or to a leucistic.
(A heterozygous gray bred to a homozygous gray will only have gray offspring. Some of the babies would still be heterozygous for leucistic, but all would be gray.



I do not know what the actual genes for Leucistic and Gray are named, but in this post, for the sake of simplicity, I am calling the gene W. Also, these outcomes are using the Punnett Square, so that is why there are 4 joeys in each breeding even though we know there are usually only 2. If you want to be a stickler, consider that each of the outcomes I show are from 2 breedings between the parent gliders, and the offspring are 2 joeys per breeding.



What Color WIll My Joey Be?

A) A heterozygous standard bred to a homozygous standard will only have standard offspring, but half of them (50%)
will be heterozygotes (carriers for leucistic).

B) Two 100% (definite) heterozygotes will produce 75% standard and 25% leucistics. 66%, or 2/3 of the standards will be heterozygous.
When a joey is sold as a 66% het for leucistic, this means its parents were both able to produce leucistics, and that joey has a 66% chance
of being able to produce a leucistic as well. It has a 66% chance of being a heterozygote, and you'll only find out for sure by DNA testing or by breeding it.

C) A leucistic bred to a homozygous standard will have only standard offspring, but all of them (100%) will be heterozygous.

D) A leucistic bred to a heterozygous standard will have 50% leucistic and 50% heterozygotes.

E) Two leucistics bred together will only have leucistic offspring.

F) Two homozygous standard grays will only have homozygous standard gray offspring.




Showing My Work:

A)
WW=standard
ww=leucistic (white)

Ww X WW

Outcomes:
WW WW Ww Ww
All are standard but 50% of them will be heterozygous.
===========
B)

Ww X Ww

Outcomes:
WW Ww Ww ww

Showing:
3 standard, 1 leucistic

Genetics:
2 standard hets.
1 standard
(the offspring showing standard coloration
have a 2/3 or 66% chance at being heterozygous,
or Ww.)
===========
C)

ww X WW

Outcomes:
all Ww standard heterozygous
===========
D)

ww X Ww

Outcomes:
Ww ww Ww ww
50% heterozygous and 50% leucistic
===========
E)

ww X ww

Outcomes:
ww ww ww ww
all offspring leucistic
===========
F)

WW X WW

Outcomes:
WW WW WW WW
all offspring standard gray


So there you have it. If I've made a mistake, please correct me, as this is all based on a little research and my assumption that the leucistic gene is recessive and the standard gene is dominant.

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#69725 - 11/22/05 08:43 PM Re: Color Genetics-leucistics and grays to start w [Re: ]
Anonymous
Unregistered


simple dominant/recessive patterns usually occur with loss of function mutations. that almost never happens in color. most color variations tend to be mutations/variations of the promoter sequence in front of the gene. that is the case in Leucistics. unlike albinos they have a fully functional melanin gene, but do not express it in their fur just in their eyes and other places we cannot see. the simplest fact is most color variations, no matter how hard people try to make them look simple, fall under the category of polygenic with incomplete penetrance. that means three things: 1. it is controlled by more than one gene, 2. even if the genetics are just right to produce a particular color variation, it may not occur because of environmental factors, and 3. figuring out inheritance trees is virtually impossible. unless you have a tree dating back 5-10 generations, with more than 10 represenatives per generation and even then it is very complicated. this is the case with buttercreams, lions, cinnamons, and most other "brown" gliders. a lot of these color variations have at least a few of the genes in common and can vary from glider to glider. thus, it is possible for two extremely cinnamon parents to produce nothing but gray joeys and vice versa. it is also a similar case with Black beauties and white faces.

calicos and ringtails result from promoter malfunctions. namely they express or dont express things in certain places-depending on a pattern or just chance.

i hope this doesnt discourage you too much but color genetics are some of the most complicated out there. there is currently many wonderful scientists working on theories in model animals, such as leopard geckos and several species of fish. their work may provide answers to these questions in a couple of decades.

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#69726 - 11/22/05 09:03 PM Re: Color Genetics-leucistics and grays to start w [Re: ]
Anonymous
Unregistered


It's interesting that the colors in gliders are so complex, making me wonder if they are more a thing of shade than true color (the browns). In horses, most color genetics are simple. Bays with 1 dilute gene are buckskin, with 2 dilute genes are perlinos, and with chestnuts 1 dilute gene makes a palomino and 2 makes a cremelo. A cremelo bred to a bay will always make a horse with 1 dilute gene (a buckskin, a palomino, a smoky black). In horses, color genetics are fairly simple. Of course there are the patterns (tobianos that are dominant and always express themselves, overos that can hide and still cause Lethal white whether you see the pattern or not) but those are pretty easy too. Has there been much research as to which genes produce which colors? Polygenes seem like a good explanation for the shaded colors (the lions, etc) but do we know which genes cause which expressions?

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#69727 - 11/22/05 11:19 PM Re: Color Genetics-leucistics and grays to start w [Re: ]
Anonymous
Unregistered


I really don't get the colors either, but it seems their is alot more than what i thought.

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#69728 - 11/23/05 12:12 AM Re: Color Genetics-leucistics and grays to start w [Re: ]
Badgersmommy Offline
Glider Slave

Registered: 04/30/05
Posts: 1382
Loc: Kentucky
Well, I'm out..I got lost in the first sentence! LOL
_________________________
Glider Kids - Badger and Bonnie, Pepsi and Grace, Victoria.. ahem..I mean ummm..Victor! and Isabella <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />

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#69729 - 11/23/05 01:42 AM Re: Color Genetics-leucistics and grays to start w [Re: ]
Anonymous
Unregistered


So far, albino and leucistics both seem to follow normal recessive patterns. WFB is definately not recessive because you can produce the trait with aWFB and a normal, only one parent needs to carry the gene... WT's are very complex and random, which makes it difficult to breed for the trait. Mosaics seem to be similar to the WFB's in the aspect that only one parent actually needs the mosaic genetics to produce the trait. Depending on what you consider platinum, it's either a combination of genes, causing a deluted coloration or, it's a variation of the mosaic gene.

Little research has actually been done on glider genetics. For the most part, what we know has been learned threw actual breedings. I don't even try to guess what type of gene each color is, but I do pay attention to how each color is produced...

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#69730 - 11/23/05 02:34 AM Re: Color Genetics-leucistics and grays to start with! [Re: ]
Judie Offline
Serious Glideritis

Registered: 10/25/01
Posts: 9173
Loc: Edwardsville, Kansas 66113
Let's not forget... once the Possible 66% or 50% Leucistic Het has produced a Leucistic... that Possible is now Proven and is now known as a 100% Het for Leucistic.
_________________________
Web site: www.MyLittleGremlin.com

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