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.