Many promoters of a hypothetical conserved gene have mostly adenines and thymines. What is the MOST likely reason for this high proportion of adenines and thymines?
A)RNA polymerases are better at incorporating uracils and thymines into RNA molecules than incorporating guanines and cytosines.
B)This is the region for separating template and nontemplate strands, and A-T base pairs are easier to separate than G-C base pairs.
C)Accessory proteins like sigma factors or transcription factors bind more easily to AT-rich sequences than they do to GC-rich sequences.
D)It is possible to create more unique sequences for recognition with adenines and thymines than it is with guanines and cytosines.
E)None of the other answer options is correct.

Question

Quizplus · Accepted Answer

The high proportion of adenines and thymines in the promoter region is likely due to the fact that this is the region where the template and nontemplate strands separate to allow for RNA synthesis. A-T base pairs have only two hydrogen bonds, which are easier to break than the three hydrogen bonds in G-C base pairs. This makes A-T pairs easier to separate, facilitating RNA polymerase binding and initiation of transcription.

Many Promoters of a Hypothetical Conserved Gene Have Mostly Adenines