1.1. Higher Tier Only

Baldness is a sex-linked inherited disorder that affects around 70% of the male population.

However, only around 40% of women are affected by baldness.

Explain why more men than women are affected by baldness.

1.2. Higher Tier Only

Baldness is caused by the dominant allele, B. Non-baldness is caused by the recessive allele, b.

Complete the Punnett square to show the outcome of a cross between a heterozygous female and an unaffected male.

Show the percentage probability of a male offspring being affected by baldness in your answer.

Percentage probability of male offspring affected by baldness ……………………… %

1.3. Higher Tier Only

The pedigree diagram in Figure 1 shows the baldness pattern across four generations of one family.

Figure 1

(i) Give the genotype of person 1 in Figure 1.

(1)

(ii) Suggest how you can tell from the pedigree diagram in Figure 1 that baldness is caused by a dominant allele.

(1)