9. The genotypes are XY and Xx. (Healthy male, carrier female).
X Y
X XX XY
x Xx xY
10. Punnett square ^. What you did wrong was for the female, you wrote XX. Remember that she’s supposed to be a carrier. That means that she carries the trait, but doesn’t actually have it (one of her X’s is defected so the other one covers for it. This is why females can be carriers and get away with it easily. Males only have one X so if that one is defected they can’t cover it up with a backup X)
11. Males 50% blind
Females 100% not blind
Remember that phenotype is the PHYSICAL APPEARANCE of an organism. If you look at my Punnett square you can see that for the females (those with two X’s), one pair is XX and the other is Xx. One of them is a carrier, but her physical appearance does not show it. So 100% of the female offspring is unaffected. For the males, however, you can see that one pair is xY. The recessive x means that they have the trait in males. So 50% of male offspring will have the trait.
12. 0 females have the disease. Look at the chart— even if they are carriers, the blindness doesn’t affect them.
3 males have the disease. The chart shows that half of all male offspring will have the trait. 6 divided in half is three.
Hope this helped at all.
