Practice question

Red-green color blindness most commonly arises from mutations or unequal crossover in OPN1LW and OPN1MW opsin genes cluster on Xq28 encoding long and middle wavelength photopigments. Males hemizygous for mutant allele manifest dichromacy with impaired discrimination, while females require two mutant copies to become affected, so population prevalence higher in males approximately eight percent versus fraction in females. Carrier females retain normal vision. Transmission shows affected grandfathers passing via carrier daughters to affected grandsons, with no male-to-male transmission, defining textbook X-linked recessive trait.