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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
To determine the father's eye colour, we must consider the genetic information provided in the question. The brown-eyed boy has at least one allele for brown eyes, which is dominant. The blue-eyed mother can only pass on an allele for blue eyes, as blue is a recessive trait.
Since the brown-eyed boy has brown eyes, he must either be homozygous dominant (BB) or heterozygous (Bb). If he were homozygous (BB), he could only inherit a brown allele from the father, which confirms that the father must also have at least one dominant allele for brown eyes.
Thus, the father must have brown eyes to produce a brown-eyed child, and the answer is (B) Brown, because at least one of the parents must have brown eyes.