Assume that you grew a culture of e. coli for many generations in medium containing 15n (from the ammonium ion), a heavy isotope of nitrogen. you extract dna from a portion of the culture and determine its density to be 1.723 gm/cm3 (call this sample a). you then wash the remaining e. coli cells and grow them for one generation in 14n, and extract the dna from a portion of the culture (call this sample b). you let the culture grow for one more generation in 14n, and extract the dna (call this sample c). each sample of dna (a, b, and c) is then subjected to ultracentrifugation. label the centrifugation profiles for the below given diagram. (note: assume that unlabeled [14n] dna has a density of 1.700 gm/cm3.)

How does natural selection change thephenotypes within a population over time?

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?

4. if a cell is placed inside a solution that has a higher concentration of solute than on the inside of the cell, what can be said about the movement of water? a. water will move out of the cell, causing it to shrivel. b. water will move in and out of the cell at the same rate. c. water will move out of the cell, causing it to swell. d. water will move into the cell, causing it to swell.