Question

Partll - Predicting Frequency of CCR5-A32 One interesting early finding about CCRS is that the frequency of CCR5-432 varies among human different parts of the world. Many populations have no or almost no ocurrence o CRS-432 in these or more, in that 16% of CR5 alleles in these populations are CCRS-432Limborska et al, 2002). Some research sug- gests that the worldwide distribution of CCR5-432 is not random or due solely to genetic drift (Galvani, 2005). Instead. may have reached higher frequencies in some populations due to selection. But selection by what? Questions 1. If HIV were the selective factor driving differences in the worldwide frequency of CCRS-432, where in the world would you expect the frequency of CCRS-432 to be the highest? Where would you expect it to be the lowest? 2. The map below shows parts of Europe, Asia and Africa. Predict the frequencies of CCRS-432 across these continents (if HIV drove selection for this allele) by coloring or shading the map below. For example, use darker shading for areas that you predict would have a higher frequency of CCRS-432. Include a figure legend showing how your shading corresponds to CCR5-432 allele frequency. Explain why you shaded the figure this way "Evolving Genetics of Disease Resistance" by Jennifer M. Dechaine Page 3

Answer 1

1) Based on HIV history, Africa is the continent were is believed that HIV originates. Nowadays is one of the continents with the highest rates of HIV. For this reason, I would choose Africa as the continent with the highest frequency of CCR5-32 based on the fact that HIV is a selective factor. On the other hand, I would choose America as the continent with the lowest frequency of CCR5-32 because It is very distant from Africa and the HIV rates are lower.

2) I shaded the figure this way based on HIV rates of each continent along the history. We observe that Africa has the darkest color because It's the continent with the highest rate of HIV, so If HIV is a selective factor of CCR5-32, this allele will be more present where HIV is higher.

Europe Asia Africa