Sex-Linked traits


In Humans,

  • sex is determined by 23rd pair [out of 23 pairs] of chromosomes
    . . - sex means internal sex organs
    . . - these chromosomes may be either X or Y chromosomes
  • Y chromosome has
    . . - one normal arm which pairs normally with the X chromosome, and
    . . - one short arm which is unlike its corresponding arm on the X chromosome
  • X chromosome has
    . . - one normal arm which pairs normally with the Y chromosome, and
    . . - one normal arm which is unlike its corresponding arm on the Y chromosome
    Sex determination
    in Humans
    Genome phenotype
    XX female
    XY male
    YY not
    viable
  • external sex characteristics (genetalia)
    . . - are coded on the normal arm of the X and Y chromosomes
  • secondary sex characteristics (facial hair; body fat distribution; etc)
    . . - are coded on one of the other 22 pairs of chromosomes.



    traits coded on the "short" arm of the XY pair are sex-linked
    exhibiting inheritance patterns with higher prevalence in males than females
    Color blindness
    (green)
    genotype phenotype
    GG normal
    female
    Gg normal
    female
    gg defect
    female
    GO normal
    male
    gO defect
    male



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    © 2004 Prof. LaFrance, Ancilla College