CAIE IGCSE Biology 17.4.16 Sex Linked Characteristic As a Feature Questions

Practise describing how a gene located on a sex chromosome can make a characteristic more common in one sex than the other.

Exam points

describe a sex-linked characteristic as controlled by a gene located on a sex chromosome
explain that sex linkage can make a characteristic more common in one sex than in the other

[Maximum number: 2]

Fig. 3.1 shows a photomicrograph of human blood.

Fig. 3.1

Haemophilia is a sex-linked blood disorder. The blood of people with haemophilia takes longer to clot.

Fig. 3.3 is a pedigree diagram showing the inheritance of haemophilia.

Fig. 3.3

□ male with normal clotting time

Figure for Question CAIE IGCSE Biology 17.4.16 Sex Linked Characteristic As a Feature Questions question 1 — CAIE IGCSE Biology

male with haemophilia female with normal clotting time
- The allele for normal clotting time is represented by $\mathbf{X}^{\mathrm{H}}$ .
- The allele for haemophilia is represented by $\mathbf{X}^{\mathrm{h}}$ .

Describe what is meant by the term sex-linked characteristic.

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CAIE IGCSE Biology 17.4.16 Sex Linked Characteristic As a Feature Questions question 1