6.1 Reproduction

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Question 32

The hairline shape in humans is controlled by a single gene. A dominant allele, $W$ , codes for a widow’s peak, while a recessive allele, $w$ , codes for a straight hairline.

Which of the following is the correct definition of a recessive allele?

A. An allele expressed only if two copies are present in the phenotype.
B. An allele expressed even if only one copy is present in the phenotype.
C. An allele that is only inherited on the Y chromosome.
D. An allele that prevents a dominant allele from being expressed.

[1]

A man who is heterozygous for a widow’s peak ( $W w$ ) and a woman with a straight hairline ( $w w$ ) have a child. Determine the probability that the child will have a straight hairline.

[3]

Calculate the probability that their next child will be a boy with a straight hairline. Use the relation:

\text{probability of a boy with a straight hairline} = \text{probability of straight hairline} \times \text{probability of being a boy}

[3]

6.1 Reproduction

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

Question 32

The hairline shape in humans is controlled by a single gene. A dominant allele, $W$ , codes for a widow’s peak, while a recessive allele, $w$ , codes for a straight hairline.

Which of the following is the correct definition of a recessive allele?

A. An allele expressed only if two copies are present in the phenotype.
B. An allele expressed even if only one copy is present in the phenotype.
C. An allele that is only inherited on the Y chromosome.
D. An allele that prevents a dominant allele from being expressed.

[1]

A man who is heterozygous for a widow’s peak ( $W w$ ) and a woman with a straight hairline ( $w w$ ) have a child. Determine the probability that the child will have a straight hairline.

[3]

Calculate the probability that their next child will be a boy with a straight hairline. Use the relation:

\text{probability of a boy with a straight hairline} = \text{probability of straight hairline} \times \text{probability of being a boy}

[3]

6.1 Reproduction

Question 32

Markscheme

6.1 Reproduction

Question 32

Markscheme

6.1 Reproduction

Question 32

6.1 Reproduction Questions

6.1 Reproduction

Question 32

6.1 Reproduction Questions