From whom has the gene for Rifat's disease come?

Correct answer: d Both his parents

For an autosomal recessive disease to show, the gene comes from both father and mother.

Why the other options are wrong

• a His father: If it came only from the father the disease would not show; the recessive gene must come from both.
• b His grandfather: It does not come straight from the grandfather; a child gets genes from the father and the mother.
• c His mother: If it came only from the mother the disease would not show; the gene is needed from both.