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Color Genetics: Ticking
http://www.nationallacydog.org/forum/viewtopic.php?f=8&t=1896
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Author:  AmberLowMiddleton [ Wed May 19, 2010 9:01 am ]
Post subject:  Color Genetics: Ticking

We discussed this in another thread, but I thought it deserved its own.

Aggie has ticking (blue spots) in the white on her chest and paws. According to popular belief, this trait is dominant, and all of her offspring should have it, too. She's had 15 puppies, and this has held true with 14 of them.

It looks like this little guy defies the rules. He has solid white on his chest and all four feet. (Excuse the quality of the picture...he doesn't really have a cone head!)

Image

Author:  Julie N [ Wed May 19, 2010 9:44 am ]
Post subject:  Re: Color Genetics: Ticking

Amber, it looks totally solid white in the photo, but does he have any faint freckles under that white? Or does the skin look evenly colored as well?

Ticking is one of those genes that is still debated. But the general consensus is that it's incompletely dominant, which opens the door for a lot of variation. A TT is going to be heavily ticked no matter what. A Tt runs the gamut and could have very minimal ticking. And remember there could be ticking that you can't see because it is in solid colored areas. Ticking is usually heaviest around the head and legs, so it is certainly possible to have a clear white chest on a ticked dog, though I'd expect to still see some spots on his toes.

It is also possible that Aggie is Tt. Considering that 14 out of 15 puppies have been ticked, she sounds TT, but what about the sires, did either one have ticking?

But everyone's favorite genetic excuse for coat color abnormalities... blame a modifier. And everything I've read said there are additional modifiers involved that affect the size, shape and density of ticking. If the puppy is Tt already and then has some sort of minimizing modifier on top of that, he could end up carrying the ticking gene but be appear spotless.

Author:  AmberLowMiddleton [ Wed May 19, 2010 9:55 am ]
Post subject:  Re: Color Genetics: Ticking

Thanks for the explanation, Julie! Most of that is way over my head, but it's interesting. It doesn't look like he has any spots on his skin.

Author:  Julie N [ Wed May 19, 2010 10:05 am ]
Post subject:  Re: Color Genetics: Ticking

Yeah, these definitions might be helpful, especially for those new to our complicated genetics discussions!

T = ticked, incompletely dominant
t = clear, recessive

TT = heavily ticked
Tt = range from heavy to very light ticking
tt = clear white

A TT dog will always pass on T to their offspring but a Tt dog could pass on either. Due to the nature of incompletely dominant genes and possible modifiers at play, it might be difficult to tell if a dog is TT or Tt. The best indications are to look at their parents and look at their offspring to see the pattern of inheritance.

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