Sex-linked Disorders
Biology: Cambridge International GCSE Supplement, topic 17.3.7
Sex-Linked Disorders
A sex linked disorder is one caused by a faulty gene that is found on the X or Y chromosome.
Colourblindness
- Red-green colourblindness is caused by a recessive allele on the X chromosome, Xr.
Genotype
- Possible female genotypes are: XRXR (normal), XRXr (normal), XrXr (colourblind).
- Possible male genotypes are: XRY (normal), XrY (colourblind).
Test yourself on Sex-linked Disorders
Which of these is not a genotype that causes colourblindness?
In comparison to females, how many possible genotypes can males have (for the colourblindness gene)?