Ahomoplasmic cell carries a. a mixture of organelle genomes. b. only one type of organelle dna. c. only one mitochondrion. d. two identical nuclei. e. only linear chromosomes.

One of the reasons that stars are so large is because

Why has two different alleles for the same trait?

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?