Genotype refers to the two alleles a person inherits for a gene. Genotyping can help determine if a person has a recessive trait, such as colorblindness, that she might pass along to her children.
Women have two X chromosomes (XX) and men have one X and one Y (XY). The recessive trait of colorblindness can only be linked to X chromosomes.
Colorblind males will have a normal Y chromosome and an X chromosome with the recessive trait, expressed as XoY, with “o” representing the color blindness trait.
Colorblind females will have two affected X chromosomes (XoXo). If a female only inherits one affected X chromosome, she will have heterozygous normal vision (XoX). A woman with heterozygous normal vision is not colorblind but will pass on the colorblindness trait to approximately half of her children.
Normal Vision Inheritance
A color blind male and a normal vision female can produce daughters with heterozygous normal vision or sons with normal vision.
Mating between a male with normal vision and a female with colorblindness can produce daughters with heterozygous normal vision or sons with normal vision.
If both father and mother have normal vision, the children will also have normal vision.
A colorblind father and a colorblind mother will produce colorblind sons and daughters.
A colorblind father and a heterozygous normal mother can have daughters with either heterozygous normal vision or colorblindness. Sons may have normal vision or colorblindness.
A mother with heterozygous normal vision and a father with normal vision can produce daughters with normal vision or heterozygous normal vision. Sons may have colorblindness or normal vision.