SexLinked Traits

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Sex-Linked Traits
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Sex-Linked Traits

• are traits whose genes are found on the X
  chromosome, but not on the Y chromosome.
• In humans, the X chromosome is much larger than
  the Y chromosome, thus it contains hundreds of
  genes more than the Y chromosome.

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• For each of the genes that are only on the X
  chromosome, females (XX) will have two alleles.
• Males (XY) will have only one allele.

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• Females with one recessive allele and one
  dominant allele for a gene that is unique to the
  X chromosome will display the dominant phenotype.
• A male, however, with a recessive allele for a
  gene unique to the X will always display that
  recessive trait because there is no other
  corresponding allele on the Y chromosome.

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Examples of Sex-Linked Genes

• In humans, hemophilia, muscular dystrophy, and
  color blindness are caused by defective recessive
  alleles located on the X chromosome.