Multiple choice

Haemophilia is a hereditary disease carried by

  1. females and expressed by females

  2. females and expressed by males

  3. males and expressed by females

  4. males and expressed by males
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Haemophilia is an X-linked recessive disorder. Females have two X chromosomes, so a defective gene on one X is usually masked by the normal gene on the other X, making them carriers. Males have one X chromosome, so if they inherit the defective gene, they express the disease.

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