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

Determine if the following statement is true or false. if true, choose true. if false, choose the rewording that is true. according to the law of independent assortment, alleles for each gene are inherited together so that they always stay together. according to the law of independent assortment, offspring express a combination of their parents' traits. according to the law of independent assortment, alleles for a characteristic split during meiosis and combine during fertilization. true according to the law of independent assortment, alleles for each gene are inherited independently so that no two alleles stay together.

Humans are believed to have evolved in coastal regions in east africa. the region had an abundant supply of fish for early humanoids to eat. when scientists analyze the fads gene they see an interesting pattern. people whose families have lived in this area of east africa for generation show a high level of diversity in alleles for the fads gene. conversely, people whose families had migrated inland a moderate distance from sources of fish showed a much lower diversity for fads gene alleles. additionally, the fads alleles found in people whose family has lived inland for generation are almost all gene alleles which produce fads proteins with a high level of function and activity. how do anthropologists explain this?

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.