Question

You are looking in an electron micrograph of several transcriptional units for rRNA. How can you tell where the transcription initiation site is?

1) It is near the longest nascent transcripts
2) It is near the middle of the Christmas tree.
3) It is near the shortest nascent transcripts
4) It is always 40 um from the center of the christmas tree.

Answer 1

The transcription initiation site can be identified by looking for the promoter sequence, which is the binding site for RNA polymerase. The correct answer is option 2: It is near the middle of the Christmas tree.

Step-by-step explanation:

The transcription initiation site can be identified by looking for the promoter sequence, which is the binding site for RNA polymerase. The promoter is usually located 5' to the transcription start site. Binding of the RNA polymerase positions it near the transcription start site, where it begins unwinding the DNA and synthesizing new RNA.

In bacterial transcription, the promoter sequence contains conserved sequences at positions -10 and -35. In eukaryotic transcription, the promoter sequence includes a TATA box. So, the correct answer is option 2: It is near the middle of the Christmas tree.