Question

The CCR5 protein is a receptor molecule on the surface of white blood cells. HIV gains entry to the CD4 cells through this receptor. A certain mutant allele of the gene for this receptor is called Δ32. Heterozygotes for this gene have reduced susceptibility to HIV and delayed onset of AIDS while homozygotes for CCR5Δ32 are resistant to HIV infection. Homozygotes with ‘normal’ CCR5 alleles are susceptible to HIV infection. You sample people from several different populations and report the following genotypic numbers data: Scandinavia: CCR5/CCR5 = 635; CCR5/CCR5Δ32 = 205; CCR5Δ32/CCR5Δ32 = 60. Austria: CCR5/CCR5 = 905; CCR5/CCR5Δ32 = 170; CCR5Δ32/CCR5Δ32 = 25. Saudi Arabia: CCR5/CCR5 = 721; CCR5/CCR5Δ32 = 28; CCR5Δ32/CCR5Δ32 = 1.

Calculate the expected frequency of CCR5/CCR5 in Scandinavia. [17] Calculate the expected number of individuals of CCR5/CCR5 in Scandinavia. [18] Calculate the expected frequency of CCR5/CCR5 Δ32 in Scandinavia. [19] Calculate the expected number of individuals of CCR5/CCR5 Δ32 in Scandinavia. [20]

Answer 1

Answer-

17) Expected frequency of CCR5/CCR5 in Scandinavia = 0.671

18) Expected number = 604

19) Expected frequency of CCR5/CCR5$\triangle$32 in Scandinavia = 0.296

20) expected number = 266

Explanation is provided below:

Genotype Phenotype 1) CORS/CCR 5 - susceptible to HIV 2) CCRS CCR5432 — reduced susceptibility to HIV and delayed onset of AIDS 37 CCR 5 4 32 | CCR 5 032 - Resistant to HIV Saudi Arabia 721 635 Senotype cces/eces (АА) CORS / CCR5432 (Aa) CCR5032/ CCR5432 205 60 Austria 905 Izo 25 | 1100 28 1 aa) 900 750 (17) Allere frequency of A=- QNAA +ONA AN (2 x 6 357 205 2x 900 1270+ 205 1800 - 1475 = 0.819 Allele frequency of a (CCR 5 A32) = 2X60 + 205. 1800 120+205= 0.181 1800 we know, Ata = 1 (Ata2 = 1 A²+ 2 Aa + a2 = 1 Expected frequency of AA in Scandinavia = A² = (0.819)2 = 0.671 Expected frequency of ceR5 / CCR5 in scadinaria = 10.671 Expected number of CORS/CCRS in scandinavia = 0.671 x 900 = 604 : (18)

(19) CCRS is denoted by O CCR5 032 is denoted by a from A²+2Aa + a2=1 Genotype ceRS / CCR 5 432 is denoted by aAa Expected frequency of CCR5/CCR 5432 in scandinavia = 2Aa = 2X 0.819 x 0.181 - 10.296 (20) Expected number of individuals of CORS/CCR5032 in scandinavia = 0.296 x 900 =266.4 ~266)