b) MWS are the genes encodes green, which has the sensitive medium wave length and LWS codes for red containing long wave length sensitive opsins are present next to each other on the X chromosome. Humans generally contain one copy of the LWS (red) gene and more copies of MWS (green) gene. Their organization and closeness denotes that they obtain by gene duplication. In this procedure, a gene is duplicated and one of the copies builds up mutations and can turn out to be new gene encoding a protein with several functions. The two contemporary opsin genes are considered to have arisen from a single gene in a primate ancestor.