Leber congenital amaurosis (LCA) is a form of inherited blindness.
LCA is a recessive condition caused by a gene mutation.
This mutation affects the production of a protein in the eyes.
The diagram below shows the inheritance of LCA in a family.
Put a crossin the box that completes each of the following statements.
The individuals that must be heterozygous for this condition are
A P and Q
B R and S
C U and V
D W and X