Q7 Probabilities


Explanation: Consanguineous marriages (between close relatives) are more often associated with recessive disorders, which fits the pattern in the last question. If you say A is “normal” and a is “mutant” for this disorder, this means you have Aa x Aa. When you draw the Punnet square, you’d get 25% AA, 50% Aa and 25% aa. Have another look if you want: link (new tab).

Let’s try another:

In this pedigree, you are counselling the family about their pregnancy. What is the probability that the next child (indicated by the arrow) will develop the condition?