The phylogenetic analysis of nucleotide sequences for a group of retroviruses has allowed researchers to discover that

there are _____ major types of HIV that originate from one ancestral lentivirus.
a. one
b. two
c. four
d. ten
e. fourteen


b

Biology & Microbiology

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Using the tryptophan operon as a model, explain a transcription pause site and the formation of a stem-loop

What will be an ideal response?

Biology & Microbiology

Muscle fibers generate maximum force:

A. at intermediate lengths. B. when pulled to long lengths before contraction. C. when contracting at short lengths. D. when the myosin filaments contact the Z discs. E. when the overlap between actin and myosin is minimal.

Biology & Microbiology

For which of the following pHs, is the

hydroxide ion concentration greater than the hydrogen ion concentration?

a. 1 b. 3 c. 5 d. 7 e. 9

Biology & Microbiology

The accumulation of free oxygen in Earth's atmosphere began with the origin of _____

A) life and respiratory metabolism B) cyanobacteria using photosystem II C) chloroplasts in photosynthetic eukaryotic algae D) land plants

Biology & Microbiology