A deletion in the human CCR5 gene makes the individual resistant to HIV-1
infection by altering the syrface receptor for the virus.
The mutant (Δ32) allele can be distinguished from the normal (1) allele by RFLP analysis with a restriction enzyme.
The 1 allele produces a 332-bp fragment and a 403-bp fragment; the Δ32 allele produces a 332-bp fragment and a 371-bp fragment.
Heterozygotes produce three bands.