2/3 or 3/4--What are the odds?

Factual Questions
1

Background:

“Lethal white” is a recessive genetic defect that causes foals to be born with an incomplete intestinal tract. It’s called “lethal white” because the same gene apparently has something to do with color. The foals are generally all-white.

It is uniformly fatal–the foal generally dies a very painful death of constipation/cholic/ruptured intestines within 48 hours. For that reason, it is recommended that they be euthanized as quickly as possible.

So, both parents are carriers of the gene. If the foal survives (which means that it did not inherit both bad genes, what are the odds that it will be a carrier?

I think it’s 2/3, since we’ve already eliminated one genetic combo. Is that right, or is it still 3/4?

2

W: non-lethal
w: lethal

The square’s result would yield three combos for a living foal-2 Ww’s and a WW. So, if you want to know the chances of the foal being a carrier, then it’d be 67% (2/3).

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