I was wondering idly the other day how many possible different individuals two humans could produce.

Each parent contributes 13 chromosomes to a child, for 26 chromosomes overall.

But for each parent it's 13 non-repeating chromosomes out of 26, and it can't be any of the same chromosomes contributed by the other parent.

So I think the formula for number of possible unique children looks like this:

(Possible combinations of 13 unique chromosomes out of 26 from Parent A) x (possible combination of 13 unique chromosomes out of 26 from Parent B) - (any results that involve duplicate chromosomes from the parents)

So while I understand the basic math of combinations and permutations (13! is the number of possible combinations from 13 objects), this particular math problem outstrips my feeble remembrances from college.

Anyone able to lay out the math for me?

Or am I merely complicating the problem, and the actual answer is 26! -- or 4x10 to the 26th power -- the number of possible arrangements of 26 chromosomes?

If the latter, I'd still like to know how to figure out the "number of combinations of 13 nonrepeating objects out of 26 total objects".

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