People who are homozygous dominant for the West Nile resista

People who are homozygous dominant for the West Nile resistance trait have the strongest resistance to West Nile Virus. Explain why these people do NOT have a heterozygous advantage, and compare and contrast this with an example we discussed in class.

Solution

CCR5 allele is involved in Westline virus infection. CCR5 is present on the surface of the white blood cells and responsible for T cells gets attracted to specific target organ. This protein is responsible for the entry of HIV virus into the cell. When this allele is in dominant state then it produces expression and reactions necessary to provide resistance to west nile virus. But when this allele is modified or mutated the resistance is partially expressed. The CCR5 delta32 is produced by mutation of CCR5. Here a 32 bp sequence is deleted and CCR5 is mutated. Both functional CCR5 alleles produced increased CCR5 molecules which bind to chemokines and produce increased immune response. If it is less then function CCR5 will be less and decreased immune response. Hence for complete resistance CCR5 should be in homozygous state.