Asked in FBISE Biology 2022 SLO — Paper 1 2022Moderate

What are phenotypes of parents of a colour blind son and non-carrier daughter with normal colour vision?

Correct answer: D. Mother: Normal, Father: Color blind

  • A. Mother: Carrier, Father: Normal
  • B. Mother: Colour blind, Father: Carrier
  • C. Mother: Normal, Father: Carrier
  • D. Mother: Normal, Father: Color blind

Explanation

Since color blindness is an X-linked recessive disease so if the the mother is color blind and the father is normal only then the son could be colorblind and the daughter would be carrier.

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About X-linked Recessive Inheritance

X-linked recessive inheritance involves genes on the X chromosome, so males express a recessive allele with no corresponding allele on their single X chromosome, while females may be carriers. Pedigrees cover haemophilia and red-green colour blindness, including carrier mothers, affected sons and the absence of father-to-son transmission.

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