Which one of the following discoveries involving dna happened first? a. avery discovered that dna was responsible for storing and passing information through generations. b. griffith learned that a chemical changed harmless cells into harmful cells. c. chargaff discovered that base pairing was consistent in samples of dna. d. hershey and chase used bacteriophages to confirm that dna was the genetic material in genes.

15 ! come and answer! a(n) disease is caused by a pathogen and can spread among organisms. a infectious b noninfectious c toxic d contaminated

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?

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