8. a stroke is a sudden loss of brain function. it results from a lack of gas exchange with brain tissue, which occurs when the supply of blood to the brain is blocked. a stroke most likely results because of a problem in the system.

What must be done to breed dogs for a partical trait

Mineral rich water heated by newly found oceanic crust escapes through cracks in the ocean floor called

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?