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Question 5 Colour blindness is inherited as an X-linked recessive condition - VCE - SSCE Biology - Question 5 - 2002 - Paper 1
Question 5
Question 5 Colour blindness is inherited as an X-linked recessive condition. It is reasonable to claim that a A. colour-blind female must have a colour-blind father.... show full transcript
Worked Solution & Example Answer:Question 5 Colour blindness is inherited as an X-linked recessive condition - VCE - SSCE Biology - Question 5 - 2002 - Paper 1
Step 1
A. colour-blind female must have a colour-blind father.
Answer
This statement is true. Since colour blindness is inherited in an X-linked recessive manner, a female (XX) who is colour-blind must have received an affected X chromosome from her father, who must therefore be colour-blind (XcY).
Step 2
Step 3
C. colour-blind male must have a colour-blind grandfather.
Answer
This statement is not necessarily true. While it is possible for a colour-blind grandfather (XcY) to pass the affected X to his daughter, a colour-blind male is not required to have a colour-blind grandfather. He could inherit the recessive condition through carrier females.
Step 4
D. colour-blind female must have a colour-blind grandmother.
Answer
This statement is also not necessarily true. A colour-blind female could inherit the affected X chromosome from either parent. Hence, her grandmother's status does not determine her colour blindness, as the gene can be passed from carrier females.