In eukaryotic cells, how do transcription factors act to control gene expression?

a. they remove introns from pre-mrna.
b. they bind to regulatory regions of dna near the genes.
c. they insert themselves into dna near the beginning of a gene.
d. they code for the synthesis of rna polymerase.

Cladistics is a way of classifying organisms by examining the characteristics of their ancestors and descendants and depicting the relationships in a cladogram. which of the following best describes a challenge in classifying organisms this way? a. there are millions of species on earth, and a cladogram is not a practical means for classifying all of them. b. it is impossible to tell which organisms are most closely related to each other using a cladogram. c. cladograms are detail-oriented and do not provide a useful understanding of evolutionary relationships. d. there is a limited number of ways to organize the information, so most cladograms end up looking very similar.