X-Linkage

Sex Chromosomes

• Heteromorphic chromosomes (XY) pair in mammalian males

• Homomorphic chromosomes (XX) in mammalian females

  • Sperm determines offspring sex

X-Linkage

• Many genes recognized as being linked to the X-chromosome (physically located on X chromosome)

• Common X-linked recessive disorders

  • Red-green colorblindness

  • Hemophilia A and B

  • Duchenne muscular dystrophy

  • Androgen insensitivity syndrome

• XY individuals cannot be homozygous or heterozygous for X-linked genes, instead they are referred to as hemizygous