Human genetics MCQ — 2 Practice Questions with Answers

Explanation

Colour blindness is commonly an X-linked recessive trait, so the relevant genes are located on X-chromosomes. Autosomes carry many non-sex-linked traits, but they are not the usual location for the classic red-green colour blindness genes. Y-chromosomes mainly carry genes related to male sex determination and do not carry the standard colour-blindness genes. Mitochondrial DNA is inherited maternally and is associated with mitochondrial traits, not the common X-linked pattern of colour blindness.

Explanation

Thalassemia is mainly caused by mutations in globin genes located on autosomes: the alpha-globin gene cluster is on chromosome 16 and the beta-globin gene is on chromosome 11. Therefore the gene is not carried on the sex chromosomes of the 23rd pair. XX and XY describe female and male sex-chromosome combinations, not the usual chromosomal location of thalassemia genes. Mitochondrial DNA is inherited maternally and is not where the globin genes responsible for thalassemia are located.