PRA and FN tests

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Clayton1977
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Posts: 22
Joined: Fri Mar 02, 2018 7:51 pm

PRA and FN tests

Post by Clayton1977 » Thu Mar 29, 2018 6:15 am

Does anyone have statistics on the health test results of pups from say, PRA or FN clear X carrier parents or carrier X carrier etc?

My dog's sire tested clear for both and his mother has not been tested for either. Her sire is clear for both and her own mother (my dog's grandmother), has not been tested. So in this case; worst case scenario for my dog would be his father being clear and his mother a carrier.

Is this likely to produce a carrier/clear litter or more likely all clear?

Apologies if this has been spoken about already but I couldn't find it anywhere on the forum.

Sgurr
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Joined: Tue Nov 17, 2009 2:22 pm
Dogs: Peggy Sue

Re: PRA and FN tests

Post by Sgurr » Sat Apr 07, 2018 11:51 am

If you breed a Clear to a Carrier, statistically 50% of the litter will be Clear and 50% will be Carrier. But in reality, it rarely happens like that. Say you have a litter of eight pups, every pup will inherit one normal (Clear) gene from its Clear parent but the gene from the other parent will be either normal (Clear) or mutant (Carrier) so think of it as flipping a coin for whether the pup will be Clear (heads) or Carrier (tails). Flip your coin eight times on the run, you could get eight heads or you could get eight tails or any combination in between, 8 heads 0 tails, 7 heads 1 tail, 6 heads 2 tails and so on until you get to 0 heads 8 tails. While the statistics predict 50% Clears and 50% Carriers when you are looking a significantly large number of litters, for one single litter, you are most likely to get a mix of Clears and Carriers - getting 8 heads in a row has odds of 1 chance in 256 (same as getting 8 tails in a row).

Similarly, if you breed Carrier x Carrier then statistically you will get 25% Clear, 50% Carrier and 25% Affected. In a single litter, anything can happen.

There is another complication though as you are looking at breeding a Clear to an Untested. You need to look at how common the mutation is in the breed population. If one in ten dogs tested come back Carrier , then the chance of your untested dog being a Carrier is 1 in 10 and the chance of it being Clear is 9 out of 10. In that case, breeding a Clear to Untested would give you good odds to get a Clear litter.

But rather than doing the maths, just test your dog........

Cheers.

Clayton1977
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Posts: 22
Joined: Fri Mar 02, 2018 7:51 pm

Re: PRA and FN tests

Post by Clayton1977 » Sat Apr 07, 2018 4:57 pm

Thanks Sgurr. For my own piece of mind I'm glad to hear a clear to carrier would produce at worst, a carrier.

And needless to say, although breeding isn't anywhere on my radar, it can't hurt to become educated on the matter.

Cheers.

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