Question

Genes for colour blindness/sex linked traits are located on

• A. X-chromosome
• B. Y-chromosome
• C. X or Y-chromosome
• D. Both X and Y-chromosomes

Answer 1

The correct option is A X-chromosome

Sex linkage applies to genes that are located on the sex chromosomes. These genes are considered sex-linked because their expression and inheritance patterns differ between males and females. Red/green colorblindness is also caused by a defective gene on the X-chromosome. You need at least one working copy of the gene to be able to see red and green. Since boys have just one X-chromosome, which they receive from their mother, inheriting one defective copy of the gene will render them colorblind. Girls have two X-chromosomes; to be colorblind they must inherit two defective copies, one from each parent. Consequently, red-green colorblindness is much more frequent in boys (1 in 12) than in girls.

So, the correct answer is 'X-chromosome'.