Assume that RNA polymerase proceeds along this template from left to right.

(a) Which end of the DNA template is 5' and which end is 3'?

(b) Give the sequence and label the 5' and 3' ends of the RNA copied from this template.

23. Write out a hypothetical sequence of bases that might be found in the first 20 nucleotides of a promoter of a bacterial gene. Include both strands of DNA and label the 5' and 3' ends of both strands. Be sure to include the start site for transcription and any consensus sequences found in the promoter.

24. The following diagram represents a transcription unit in a hypothetical DNA molecule.

(b) If this DNA molecule is transcribed, which strand will be the template strand and which will be the nontemplate strand?

(c) Where, approximately, will the start site of transcription be? What would be the most likely effect of a mutation at the following locations in E. coli gene?

A strain of bacteria possesses a temperature-sensitive mutation in the gene that encodes the sigma factor. At elevated temperatures, the mutant bacteria produce a sigma factor that is unable to bind to RNA polymerase. What effect will this mutation have on the process of transcription when the bacteria are raised at elevated temperatures?

The following diagram represents a transcription unit on a DNA molecule.

Transcription start site

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