Hello everyone ,

I have a question concerning formulas. I feel that it should be easy to solve but I can't figure out how to do it myself
So, I am working on mutations frequencies and I want to calculate the probability to be homozygous (ie have two mutations together).

My excel is like this
mutation freq
A 4.19E-06
B 4.17E-06
C 4.12E-06
D 3.28E-05
and it goes until >300 rows ><"

What I want should be prob of A to "meet" A, B, C and D ... = A*A + A*B + A*C + A*D ...
And then B to "meet" A, B, C and D ... = B*B + B*C + B*D ... (no B * A because it was in the previous one)
and so on ...

And in the end I want the sum of all the probabilities.

Is there any formula I can apply for my problem.

thank you very much!