Question

Which two major genes are responsible for eye colour in humans, and on which chromosome are they located?

Options

• A and B genes on chromosome 1

• Genes C and D on chromosome 21

• OCA2 and HERC2 genes, both located on chromosome 15

• Genes Y and Z on the X chromosome

Answer 1

The two major genes controlling human eye colour are OCA2 and HERC2, both located on chromosome 15. However, at least 16 genes in total contribute to eye colour variation, and some eye colour genes are partially X-linked. This demonstrates that even with identified major genes, polygenic inheritance involves multiple genetic factors working together to produce the final phenotype.