Color blindness is
a recessive trait. The gene for color blindness is on the X-
chromosome. The family tree below shows the trait of color blindness. The
only unknown is the mother in the first generation.
I.
I1.
What must be true about the mother?
A. She is a carrier for color blindness.
B. She only has one X chromosome.
C. She is color-blind.
O D. She has no recessive color blindness alleles.