Distortion of allele and genotype frequency in HIV positive and HIV negative individuals. Monique FergusonBio- 475 Dr. Lin
Rationale • The variation of allele and genotypic frequency between HIV positive and HIV negative individuals on the basis of polymorphisms, potential involvement in retroviral infection or pathogenesis, and their genetic location.
Independent vs Dependent variable • The independent variable: HIV positive and HIV negative individuals • The dependent variable: Difference in genotype distribution between infected and HIV uninfected groups
Genetic Profile involved in immune response (figure 2) All the genes in the genetic profile were found in both HIV infected and uninfected individuals. All of the genes were the same except the CKR5 gene which is only found in an individual who had the delta 32/ delta 32 allele. This type of person would be HIV negative.
CKR5 genotype distribution among HIV-1-seropositive and HIV-1-seronegative individuals +/+: 2 standard CKR5 alleles +/ delta 32: One standard and one mutant gene delta 32/ delta 32: 2 mutant alleles In the figure above in order for an individual to not become infected with the HIV virus they had to possess 2 copies of the mutant CKR5 allele. The results show that infected individuals did not possess this gene whereas 3 percent of the uninfected individuals possessed this recessive gene.
Conclusion • A CKR5 genotype which consist of 2 pairs of mutated alleles are found only in HIV- negative individuals • This homozygous pair allows the individual to remain HIV negative by not allowing virus to attach to CD4 cells
References • Dean, M. et.al. 1996. Genetic Restriction of HIV-1 Infection and Progression to AIDS by a Deletion Allele of the CKR5 Structural Gene. Science 273:1858-1862 • O’Brien, S., J. M. Dean. 1997. The Search of AIDS-Resistance Gene. Scientific American 44-51 (http://www.sciam.com/0997issue/0997obrien.html)