Which allele combination represents a male who has an X-linked recessive disorder? XrY XRY XrXr XRXr

XrY

Explanation:

i guess the R shows the dominancy, R dominant r recessive where the r followes the X, meaning it is X-linked

The allele combination XrY is the allele combination of X linked recessive disorder in a male.

Explanation:

A human male has one X chromosome and one Y chromosome which makes them heterogamous. Females have two copies of X chromosome and thus they are homogamous. Due to the presence of just one X chromosome chances for males getting affected by the disease is more.

Haemophilia and muscular dystrophy are X linked recessive disorders. Females with one affected X chromosome act as carriers but won't have the disease. For a female to be affected with the disease both the X chromosomes should be affected.