Question

Which is not an X-linked recessive disease?

• A. $\beta$-thalassemia
• B. Haemophilia
• C. Colour blindness
• D. Glucose 6-phosphate dehydrogenase deficiency

Answer 1

The correct option is A $\beta$-thalassemia

Colour blindness and hemophilia are X-linked recessive disorder because the governing genes are present on X-chromosome, therefore these diseases are inherited from parent to offspring in sex-linked manner. These disorders are mostly expressed in males because males are hemizygous for chromosome and can express the recessive gene also. Females have two X chromosomes and hence, need two copies of the affected gene to cause the disorder. This means that both disorders are recessive. $\beta$-thalassemia is a blood disorder which is caused by the mutation in the Hb${}^b$ gene present on chromosome 11 and is inherited in an autosomal recessive manner. Glucose-6-phosphate dehydrogenase deficiency is a genetic disorder that causes the destruction of red blood cells is called as hemolysis. It is due to defect in gene present on X-chromosome which codes an enzyme called glucose-6-phosphate dehydrogenase. The correct answer is A.