If a colour blind woman marries a normal visioned man, their sons will be
- All normal visioned
- Three-fourths colourblind and one-fourth normal
- One-half colourblind and one-half normal
- All colourblind
Answer
(4) All colourblind
Solution
As per NCERT, colour blindness is a sex-linked recessive disorder due to a defect in a gene on the X chromosome.
⇒ Colour blind woman: XcXc; normal man: XY
⇒ XcXc XY XcX (daughters, carriers with normal vision) + XcY (sons)
∵ Sons receive their only X chromosome from the mother, which carries the defective gene.
∴ All sons will be colour blind.
Answer: (4)