SEX LINKAGE

Question 1

How do sex-related conditions occur? (2)

Answer 1

• Females have 2 X chromosomes so 2 copies of the gene.

- males have one so whichever allele they have is the one expressed.

Question 2

Haemophilia (3)

Answer 2

• can’t produce enough of 1/13 blood-clotting proteins
• causes excessive bleeding
• X^H = normal X^h

Question 3

Duchenne Muscular Distrophy (DMD) (3)

Answer 3

• X-linked distrophin allele
• distrophin codes for glycoprotein that stabilises muscle fibres.
• loss of mass & progressive muscle weakness

Question 4

Pedigree diagram

Answer 4

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