Fill In The Blank. In three separate site-directed mutagenesis experiments, scientists altered a Lys residue in corn PEP carboxylase to an Asn, Glu, or Arg. The substitution that you would expect to have the least effect on enzymatic activity would be because it, like Lys, is charged at physiological pH. The substitution that you would expect to have the most effect on enzymatic activity would be because it is charged at physiological pH. (Use structure tables if you need to.)

92 sathe best for the question 11. most animals and plants reproduce sexually. this means that dna is passed down to new organisms from two parental organisms. which of the following is a key advantage of sexual reproduction?

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.

Plant species a has a diploid number of 12. plant species b has a diploid number of 16. a new species, c, arises as an allopolyploid from a and b. the diploid number for species c would probably be a) 12. b) 14. c) 16. d) 28. e) 56.