Q8 more probabilities

OK, you’re clearly good at this.

Explanation: So, we’ve have autosomal dominant before, I expected you to get this right! However, I wondered if you might be tricked by there already being 3 affected children. As you know, when we have Aa parent x AA (A = normal, a = mutant). Each child will either get a “A” from the father or a “a” with equal likelihood of both. If they get the “a” then they will have the disorder. Therefore, 50/50. The important point to remember though is that each child is independent; just because you have three affected already doesn’t change the odds of the next one being affected as well.

Try this one!

For this rare condition… If A is the normal allele and a is the pathogenic mutant, what is the likelihood of this person having the genotype Aa

(answer explained on the correct answer page!)