Grey gene test question (UPDATED RESULTS)

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May 20, 2008
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I just sent in a grey test to determine the zygosity for my mare, Magic. It came back GG, or homozygous for the grey gene.

I also sent in a grey test for her new colt, Moonie. It came back gg, or not carrying the grey gene. It was my understanding that a GG horse would pass at least one greying gene to its offspring. But that doesn't seem to be the case with Magic and Moonie.

Now I SAW him come out of her so I KNOW that he is hers. Am I just misunderstanding the test or did something go wrong here?
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Something went wrong, maybe you contaminated the samples? Or someone did a typo! I would ask the lab, did they know it was mother and son when they tested?

No way can a "gg" come from a "GG" parent! Offspring has to be Gg, somewhere something got mixed up!

Let us know what you find out!
I have sent them an email explaining the situation and asking what they think went wrong. I was actually hoping that the mare was Gg and would have only passed on the g making the little colt (gg). So, yeah, I was thrilled when I opened the email and saw that he was only gg! Then I saw her results and thought "Something is not right"

Will let you know if I hear back from the lab.
I'll also be interested to hear what the lab says!

It's my understanding that a horse can only be homozygous for grey if both parents were grey. Is this true?
Well, dog gone it!!! I was so excited about this new test for grey! I sure hope they get the bugs worked out soon! Keep on top of this. If the test is not going to be accurate then it is useless. You should definantly get your money back for those tests.
Have you heard back from them yet? We have a colt I'm planning to test but not if I'm going to just be as confused as ever
You're referring to 'true' grey, right? Not silver?

The gene for true grey is dominant, which means that if they got it, they show it, even if just one copy. For the dam to be GG, BOTH of her parents would have had to be true grey. If the results are mistaken, and the mare is Gg, then the foal could very well be gg--no gene for true grey. You are correct in your assessment that if the mare is a true grey, and is GG, there should be no way the foal could be gg!

Yes, keep us posted! I think everyone would like to know if the testing is indeed accurate-as said, no point in paying to have it done if it is demostrably not accurate!!

Okay, I called and talked to Arnie. He is not the one that did the original tests, but he pulled them out and went over them. Moonie, my little colt, is indeed gg. He said that one they knew for sure because it is easy to see that there is no grey mutation. This is the outcome that I was hoping for as he is a black/white pinto and I really didn't want him to grey out.

Arnie said that it gets trickier when trying to determine zygosity on a horse that carries the grey gene. He said that where they have only one marker (not sure that this is what he called it) to check for to determine zygosity for tobiano, red/blk factor, agouti, etc. there is several thousand that are present for grey zygosity. Therefore they have to run the test many times and then take all those results in mind to make a decision on wether the horse is GG or Gg. Arnie said that he reread all the results on my mare and said that she is indeed only Gg. I knew she would be either Gg or GG as both parents are listed as grey and she is definetely grey herself.

I am thrilled with these results. I have seriously been thinking about keeping this little colt for a future stud and now this makes the decision even easier.

Here are pics of my mare, Magic, about 2 weeks before she foaled:


And here is her colt, Moonie:


Sorry, couldn't resist the opportunity to share their pictures!
Good to know that the test is accurate for determining whether the horse is grey or non-grey.

You could have saved money by testing just Moonie; since he is gg you then know without testing that his dam is Gg
"You could have saved money by testing just Moonie; since he is gg you then know without testing that his dam is Gg"

(Got to figure out this quote thing!)

Yeah, I have since thought this myself. Hindsight is 20/20! And sometimes my "mommy brain" doesn't work to its full ability!
Thanks for the update!!! The way you explained it makes sense.

Moonie looks like a little stuffed animal in that picture! What an expression!!!

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