Why is color blindness observed in more males What is the ge

Why is color blindness observed in more males? What is the genotype of a male with color blindness? A female with color blindness? A female that is a carrier for color blindness?

Solution

Color blindness is more prevalent among males than females, because the most common form of color vision deficiency is encoded on the X sex chromosome. Red-green color blindness is in the majority of cases provoked through a defective X-chromosome. Human beings have 23 different pairs of chromosomes whereof one pair is the so called sex-chromosome. This pair consists of two X-chromosomes on women and one X- coupled with one Y-chromosome on men. Color vision in the red-green area is coded on the X-chromosome which is called a sex linked trait. It is sex-linked: genetic red–green color blindness affects males much more often than females, because the genes for the red and green color receptors are located on the X chromosome, of which males have only one and females have two.

The genotype of a male with colorblindness is X^bY. The genotype of a male with normal vision is X^BY. ... The genotype of a female who has normal vision but is a carrier of the disease gene is X^BX^b.

The genotype of a female who has normal vision and is not a carrier is X^BX^B. So, for a male to be colour blind the faulty colour blindness \'gene\' only has to appear on his X chromosome. For a female to be colour blind it must be present on both of her X chromosomes. If a woman has only one colour blind \'gene\' she is known as a \'carrier\' but she won\'t be colour blind. On women the not defective chromosome is in charge and therefore she is not colorblind but a carrier for color blindness. Because a women needs two defective X-chromosome to be affected this symptome is called X-linked recessive.