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mikeee mikeee
wrote...
13 years ago
I'm trying to calculate the COI of a dog but seem to get the wrong COI based on two different software.
The dog is line breed on 3 dogs, 4-5, 4-5, 3-4. The 3 dogs are outcrosses. The 2 softwares give me 1.5625%.

When calculate it by hand, I get 2.34375%.
4-5 -------> 0.00390625
4-5 -------> 0.00390625
3-4 -------> 0.015625

What am I doing wrong?

Thank you,
Mike
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5 Replies

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Replies
wrote...
Valued Member
Educator
13 years ago
I've never come across such a problem, but I will give it a shot. Are you using this formula ?

COI = sum[ (.5 ^ (a + b + 1)) * (1 + c) ]

a = Generations between sire and common ancestor
b = Generations between dam and common ancestor
c = COI of common ancestor

or this rendition: FX  =  Sum of [ {½) n1+n2+1 (1 + FA)]

Just to make sure we are on the same page: COI is the probability that a homozygous gene pair will be identical by descent from both sides of a pedigree. In the formula, FX is your dog’s COI, FA is that of the ancestor common to both sides of the pedigree. n1 and n2 are the numbers of generations on each side between your dog and that ancestor.
mikeee Author
wrote...
13 years ago
I was trying to calculate the COI using the path analysis technique. When I used the formula I also didn't get the correct answer. If someone please help me with part of this problem I will figure out the rest.

4-5 would be .5 ^ 8
3-4 would be .5 ^ 6
wrote...
Donated
Valued Member
13 years ago
Hey mike, I just want to mention that with statistical software such as SAS, etc., data often times comes out skewed when data is limited. Thus, that discrepancy you're seeing doesn't necessary mean you've done calculations by hand wrong.

Anyways I found some info that might help you out if you follow these steps.

1. Re-draw your dog’s pedigree, but instead of writing it out in the traditional manner, every time the same name appears on both the sire’s side and the dam’s side, write the name only once.

2. Draw a path from your contemplated litter to the litter’s sire, back through each of the sire’s ancestors to that common ancestor.

3. Do the same through your dog’s dam. Now you should have a circular path through several generations that goes via both the sire and dam’s sides of your dog’s pedigree.

4. Count the number of steps in the circular pathway from your dog to the common ancestor, and subtract 1 from that number.

5. The contribution of each step in the pathway is (1/2)n, where n is the number you got in step 4. For example, for three steps: (1/2)2 is 0.25.

6. Many dogs will have more than one ancestor common to sire and dam, so repeat these steps for each common ancestor.

7. Add the contributions of each path together. For example, [if the sire and dam had three common ancestors): (1/2)3 + (1/2)4 + (1/2)6 ) to obtain the F value, also called the coefficient of inbreeding (COI). In this example, F = 0.125 + 0.0625 + 0.015625 = 0.203125, or a COI of about 20 percent.

8. COI increases if the common ancestor is itself inbred. The adjustment to the calculation is made by multiplying the (1/2)n result by (1 + Fa), where Fa is the COI of the common ancestor. If the common ancestor had a COI of 0.0125, then you would multiply the (1/2)n value by 1.0125.
mikeee Author
wrote...
13 years ago
Well, star, I did a research on COI so all this info I already know.......thank you for taking the time to post it!

I just need help figuring out the different values. When I used the different softwars, I input all dogs in the first 5 generations to keep it simple for me to calculate by hand.

 Let me give more details maybe someone could point out the mistake I'm making:
The dog I calculating the COI for is Fenja. She is linebreed 4-5 on Ellex.
The path would be:
Fenja-Sven-Gotz-Alf-Ellex-Alf-Don-Muchta-Sindy-Fenja

so this would be .5 ^ 8, correct?
wrote...
Valued Member
Educator
13 years ago
According to that formula star posted, 0.5 ^ 8 seems correct. On a side note, I found an online calculator that may help you out:

http://kippenjungle.nl/COI/COIcalculator.html#start
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