What Is the Genotype of a Colorblind Female?

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.

Colorblindness Genetics

• 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.

Male Genotype

• 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.

Female Genotype

• 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.

Colorblindness Inheritance

• 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.