Researchers noted that about half of all species of bacteria contain small segments of dna of about 20–50 base pairs derived from plasmids or viruses. the phrase clustered regularly interspaced short palindromic repeats (crispr) describes the organization of these viral dna segments in the bacterial genome. bacteria use crispr to: (select all that apply.) identify viral dna by complementary base pairing with template dna. transcribe rna that combines with a protein that has a dna-cleaving function. copy part of the bacteria genome and incorporate it into a viral genome. transcribe rna that combines with a protein that has a rna-cleaving function. "remember" the first time it was infected with a virus. identify viral dna by complementary base pairing with rna.

To answer this question, researchers studied populations of the dusky salamander (desmognathus ochrophaeus) living on different mountain ranges in the southern appalachian mountains. the researchers tested the reproductive isolation of pairs of salamander populations by leaving one male and one female together and later checking the females for the presence of sperm. four mating combinations were tested for each pair of populations (a and b)—two within the same population (female a with male a and female b with male b) and two between populations (female a with male b and female b with male a). the proportion of successful matings for each mating combination was measured. for example, when all the matings of a particular combination were successful, the researchers gave it a value of 1; when none of the matings were successful, they gave it a value of 0. then the researchers calculated an index of reproductive isolation that ranged from 0 (no isolation) to 2 (full isolation). the reproductive isolation value for two populations is the sum of the proportion of successful matings of each type within populations (aa + bb) minus the sum of the proportion of successful matings of each type between populations (ab + ba). the table provides data for the geographic distances and reproductive isolation values for 27 pairs of dusky salamander populations.

20. in humans, freckles are dominant to no freckles. trey has no freckles and his wife anna grace has freckles, but her dad doesn't. they want to know what percentage of their kids would look like trey. show a punnett square to support your answer.

The two tubes contain bromothymol blue. after 24 hours, what will the color of the water be in tube b? a. green (it won't change) b. yellow c. blue d. colorless (clear)