When the gene encoding a certain cytoskeleton protein is deleted, the resulting mutant cells round up and do not form their normal appendages. These mutants can be rescued when a gene encoding an N-terminal green fluorescent protein (GFP) fusion of the protein is expressed, but not when a gene encoding a C-terminal GFP fusion is expressed. Which fusion protein is appropriate to use in studying cellular localization and activity

Astudy by solloch and et. al., in 2017, gives the map above which shows the frequency of alleles with a ccr5-delta32 mutations over 87 different countries. this mutation deletes the presence of a co-receptor (ccr5) on the outside of human t-cells (lymphocytes). some viruses, such as the one responsible for the black death and human immunodeficiency virus (hiv), require this receptor for attachment to host cells during the infection process. the black death was an epidemic that passed over northern europe during the 14th century killing nearly 60% of europeans. according to this information, which explanation best explains why northern europeans show a greater immunity for hiv than some other parts of the world?