genetics of coat type

[Julia Hunt]

Can someone explain the genetics of rough vs smoothcoat ?

 

Thanks Julia

[BPoole]

To my understanding, smooth is the dominant. I don't fully get it all myself, but if you were to have a smooth and a rough produce a litter, smooth would dominate. But you have to factor in if the parents of this litter are SS (smooth) Ss(smooth, carrier of rough) or ss (rough). Others will have more to add I'm sure.

[Julia Hunt]

So, is it the case then that a smooth to rough breeding would either be all smooth (if the smooth parent didn't carry the gene for rough coat)? Or, if the smooth parent carried the rough gene, the litter could be anything from all smooth to all rough, but statistically would be 50/50?

 

Julia

[brookcove]

Yes, your smooth may carry the rough gene so may produce roughs if bred to another dog, whether smooth or rough, which also carries a rough gene.

 

All roughs carry two rough genes. So they will pass one rough gene to every pup in the litter. Whether or not an individual pup actually is rough depends on whether they get a smooth or rough gene from the other parent. If they get a smooth gene they will be smooth but carry the rough gene as well. If they get a rough gene they will be rough.

 

I know it doesn't matter much in the big picture but I love to puddle around in the edge of the gene pool.

 

Riddle me this: I struck up a conversation with a lady in my son's gym class. Her purebred, papered Golden Retriever had gotten in with her neighbor's purebred, papered brindle Boxer. The accident happened right before her owner's eyes and was the only opportunity she had. Imagine her surprise when eight beautiful, solid BLACK clearly boxer pups were born. Brindle to sable equals black?

 

I figure brindle is like tri or merle and the Boxer is really "black brindle" though it's not called that (right?). Anybody know for sure?

 

And yes, the Golden is scheduled for a trip to the vet as soon as pups are weaned - lesson dearly learned on that family's part.

 

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Rebecca

Brook Cove Farm, NC

[amc]

OK on the smooth/rough part, but what about the pups who have 'medium' coats? Not quite smooth, but not excessively rough either?

 

Thanks for any info,

 

Amy

 

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Amy Coapman

Montague, in the State of Jefferson

[Bill Fosher]

Yes, Amy, that was my question. I seem to have a bunch of dogs here that aren't exactly either smooth or rough. If it's really just a simple recessive, is it that anything that isn't perfectly smooth is considered rough? In which case, I think I see more rough-coated dogs than smooth.

 

 

 

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Bill Fosher

Surry, NH

[Julia Hunt]

Yes I'd like to understand about medium's too. Are they roughs with some other gene influencing how long the coat is? Some roughs are profusely coated (and not just in the Barbie collies).

 

Julia

[Guest PrairieFire]

Ah, the wonders of genetic complexity...

 

Most genetic expression obviously isn't easily catalogable...

 

In the cases where we suspect (please note the use of the word) we have the right information (CEA comes to mind), intensive, direct research has been done...

 

 

 

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Bill Gary

Kensmuir, Working Stockdog Center

River Falls, WI

715.426.9877

www.kensmuir.com

[Pipedream Farm]

Even among our smooth-coated dogs there is variation in what I'll call coat thickness. We have one that has what I'd call a "skin-coat", she has a very short & fine coat that it lays very close to her skin. On the other extreme we have one that has a short but very thick coat; there is so much fur the fibers stand straight out from the skin. Perhaps, this might be better described as the thickness of the undercoat.

 

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Mark Billadeau

[Deacon Dog]

Based on some things I've read, there's a genetic timing mechanism that affects identical traits. For instance, the gene for the shape of the muzzle is the same for the Boxer and Golden Retriever. The Boxer's muzzle, however, is told to stop growing before it gets to be as long as the Golden Retriever's. This explains why breeds look almost identical (except for coat color) when born but so different as adults.

 

Maybe the same thing is going on with coat length, i.e. there are all sorts of different timing mechanisms telling the coat when to stop growing, and it's not as simple as smooth or rough. Perhaps someone who knows more about genetics will chime in.

 

Tony Luper

Summerfield, NC

[Eileen Stein]

My understanding is that coat length is polygenic. There is one basic gene at the S locus with an allele for short (dominant) and an allele for long (recessive). But there are other genes that also influence how long is long and how short is short (as well as other aspects of coat type such as density and waviness), so the range of possible coat lengths is pretty much a continuum.

 

As for the golden retriever, I remember reading long ago, before I really knew anything about dog genetics, that any offspring of a golden retriever mother and a non-golden retriever father (and vice versa, presumably) would be black. I recall this vividly because at the time I had a mixed breed bitch whose mother was a purebred golden, and she in fact looked just like a black golden retriever. Unfortunately, I don't remember where I read it, or what the alleged genetic basis for this was. I can't vouch for its accuracy; it might not have been true at all. But I'll look around and see if I can track it down.

 

[This message has been edited by Eileen Stein (edited 01-15-2003).]

[JEL]

Eileen,

as a (former) Golden Retriever owner, I do find that interesting. I believe there is some merit, too...how else to explain purebred Golden Retrievers born with black hairs...or spots on the body.

(it is in fact written into that breed's standard, that any noticable areas of black on the dog's body to be seriously faulted.)

I can't explain it...but I know it happens for a fact.

 

Janet

[SoloRiver]

Any character that varies continuously (like height in humans, or coat length in Border Collies) is likely to be polygenic.

 

I have one of those in-between dogs. Fly could be described as medium-coated. She has a short, thick, Labrador retriever-like coat that's a bit longer around the neck, over the shoulders, and on her breeches. Anyone who thinks s/he wants a shorter coated dog because "they shed less" needs to meet Fly. At least I can pick Solo's hair off of stuff; hers gets wound into fabric, flies around aimlessly in the air, and ends up in all my food somehow.

 

I used to refer jokingly to Fly's coat as "shlong" (short-long) but some people, er, misunderstood me.

 

The sort of stuff Tony's talking about has to do with what are broadly called regulatory genes -- genes that direct the function of other genes. An interesting and oft-cited example are the homeobox genes that control early development in animals. Fiddling with homeobox genes in fruit flies gets you interesting things like flies with two sets of wings (when the genes that build the thorax are instructed to make the segment twice instead of once), or legs on their heads where antennae should be. We have homeobox genes that are homologous to those of fruit flies, and worms, and mice, a nice illustration of the common ancestry of all animals. Other genes control developmental timing, which can get you a whole host of correlated changes. Some people who think dogs are paedomorphic wolves whose development has essentially been frozen in puppyhood. (Others disagree or find this explanation too simplistic.) For that matter, there are plenty of scientists out there who consider humans to be paedomorphic apes. (Also a matter of debate.)

 

More about homeobox genes: http://www.biosci.ki.se/groups/tbu/homeo.html

 

Disclaimer: I am not a geneticist. I am just a random person who studies evolution.

 

About Golden retrievers: apparently the root stock they were developed from were mostly black dogs. The occasional gold one that popped out was highly prized. I would have guessed that the gold dogs would be homozygous recessive but perhaps that isn't the case. I remember reading a discussion about how Golden crosses frequently end up being black and that the heritage of the Golden is the reason why, which would mean that the Golden parent was helping to determine the black color and not just being "swamped" by it, which would mean that there is some sort of modifier gene (I am probably using that term wrong) that gives gold color (rather than the simple recessive that produces red in Border Collies). Hmmm. Oh, this site on color genetics in dogs says gold is a result of e, recessive red, which overrides whatever is at the A locus, which determins pattern of black (all black, brindled, etc.). So, then the black Golden crosses make sense because the other parent doesn't have the e ("little e") at the E locus, and e is recessive so both parents must have it to end up with gold pups.

http://bowlingsite.mcf.com/Genetics/ColorGen.html

 

The last part of the mystery is that apparently there are sometimes black puppies in Golden retriever litters. They must be due to new mutations? (As a total aside, I also know of a litter of Rhodesian Ridgebacks who all came out black and tan -- Dobermann color. This apparently happens with some frequency in RRs.)

 

Oh well, better get back to work.

 

-- Melanie, Solo the recessive red, and Fly the somewhat bristly

 

[This message has been edited by SoloRiver (edited 01-15-2003).]

[BPoole]

Ah, Melanie, they need to meet Pepper along with Fly. She's got SHORT fur and sheds like a monster! Tacoma, wavy medium coated, sheds moderately, and Yu-Gi, somewhere between smooth and medium, NEVER sheds. Go figure.

 

BTW, Pepper and Tacoma are half sibblings. Both Pepper's parents were smooth, but carry rough. She was the only smooth in the litter. Tacoma's mother was very rough, and he came out medium. Don't you love how in just one breed you can have so many variations.