Sex Linked Traits


I.    Sex Chromosomes

      The sex chromosomes are the 23rd pair of chromosomes in Humans.

       Females have two X chromosomes (X X)

      Males have one X chromosome and one Y chromosomes (X Y)

      The X chromosome is considerably larger than the Y chromosome therefore there are many traits that are     associated with the X chromosome; these are called sex-linked traits.


II    Sex Linked Traits

      Color Blindness is an example of a sex linked trait.  The gene for color blindness is found on the X chromosome. 

    Females have two X chromosomes therefore they could have normal vision XX;

    Females could be a carrier for colorblindness (Xl X);

    or Females could be colorblind (Xl Xl ).

    Males can either have normal vision (X Y); or

    Males can be colorblind (Xl Y ).  Since Males only have one X chromosome they cannot be a carrier; they will either have the trait, or not have the trait.