Question

During transcription the site of DNA molecule at which RNA polymerase binds is called __________.

• A. Promoter
• B. Regulator
• C. Receptor
• D. Enhancer

Answer 1

Answer:

A. Promoter

Promoter Site

• The specific region on a DNA molecule where RNA polymerase initiates transcription is known as the promoter.

• It acts as a recognition site that signals the beginning of a gene and directs the RNA polymerase to the correct strand for transcription.

• Binding Mechanism: The promoter sequence is recognized by the sigma factor (in bacteria) or transcription factors (in eukaryotes), which recruit RNA polymerase to the DNA template.

• Directionality: Promoters define the direction of transcription and specify which of the two DNA strands will serve as the template.

• Conserved Sequences: In prokaryotes, promoters often contain conserved sequences located at specific distances from the transcription start site, such as the -10 element (Pribnow box) and the -35 element.

• Eukaryotic Promoters: Eukaryotic genes often feature a conserved promoter element called the TATA box, located approximately 25-30 base pairs upstream of the transcription start site.

• Promoter: The upstream sequence that initiates transcription.

• Terminator: The sequence that signals the end of transcription.

• Operator: A segment of DNA where a repressor binds to prevent transcription (often found in bacterial operons like the lac operon).

• Enhancer: Regulatory DNA sequences that increase the rate of transcription, often located far from the gene they regulate.