Punnett square 5

Dr. Foster (Teacher): ‘Great work, everyone. With Punnett square 5, we’ve confirmed that when one parent is a carrier (Aa) and the other is completely unaffected (AA), none of their children will develop thalassemia, but half could end up as carriers themselves (Aa).’

Eleonore introduces a new scenario: ‘Suppose one parent actually has thalassemia (which we label as aa) and the other parent is just a carrier (Aa). In that case, what is the probability that a child will inherit two copies of the recessive allele and thus have the disease?’

Consider these options carefully and select the correct probability: