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In humans, brown eye colour is dominant and blue eye colour is recessive - HSC - SSCE Biology - Question 8 - 2009 - Paper 1
Question 8
In humans, brown eye colour is dominant and blue eye colour is recessive. A brown-eyed boy and a blue-eyed girl have a blue-eyed mother. What eye colour does the fa... show full transcript
Worked Solution & Example Answer:In humans, brown eye colour is dominant and blue eye colour is recessive - HSC - SSCE Biology - Question 8 - 2009 - Paper 1
Step 1
What eye colour does the father have and why?
Answer
The father of the brown-eyed boy must have brown eyes. This is because the mother has blue eyes, which means she can only pass on the recessive blue allele. Since the boy has brown eyes, he must have inherited the dominant brown allele from his father.
In terms of genetics, the genotype of the mother is homozygous recessive (bb) for blue eyes, while the son must be at least heterozygous (Bb) for brown eyes, indicating that the father must contribute the dominant brown allele (B). Therefore, the correct answer to the question is option (B): Brown, because at least one of the parents must have brown eyes.