Final answer:
Trichromatic vision in humans is a result of gene duplication, providing three types of cone cells responsive to different wavelengths, enabling color vision. Red-green colorblindness is more common in men due to the X-linked inheritance of the gene associated with color vision.
Step-by-step explanation:
Humans have approximately 20,000 protein-coding genes, each responsible for various traits and functions, including those associated with vision. Our ability to see in color, specifically trichromatic vision, is due to the presence of three types of cone cells within our eyes. Each type of cone cell is sensitive to different wavelengths of light: S cones to short wavelengths (420 nm), M cones to medium wavelengths (530 nm), and L cones to long wavelengths (560 nm). Gene duplication has allowed for the evolution of this complex visual system by providing a means for genes to diversify without losing their original function, which is an essential aspect of evolution.
Red-green colorblindness is an inherited trait, more common in men due to the X-linked nature of the genes responsible for color vision. This is because men are hemizygous, having only one X chromosome, and therefore one copy of the gene that determines color vision. If there is an issue with this gene, there is no second copy to compensate, leading to color blindness. Women, however, have two X chromosomes and are less likely to be colorblind, as the likelihood of having a defect in both copies of the gene is much rarer.