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Transcriptional initiation is mediated by the direct interaction of:

A) RNA polymerase and mRNA
B) RNA polymerase and promoter
C) Promoter and mRNA
D) DNA polymerase and template DNA

User Ron Diel
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Final answer:

RNA polymerase directly interacts with the promoter during transcriptional initiation, attaching to a specific promoter DNA sequence to start the transcription process. The promoter determines the binding site for RNA polymerase, and this interaction does not involve mRNA.

Step-by-step explanation:

During this process, RNA polymerase, together with transcription factors, binds to a specific promoter DNA sequence to form the initiation complex. This is a critical step where the DNA double helix unwinds to form a transcription bubble, allowing RNA synthesis to begin. The promoter, a DNA sequence that is located typically 10 to 30 base pairs upstream of the gene, guides the binding of RNA polymerase. This enzyme is capable of synthesizing RNA from a DNA template without the need for a primer and adds ribonucleotides in the 5’→3’ direction of the newly forming RNA strand, complementary to the 3’→5’ direction of the template DNA strand. Consequently, transcription involves the creation of a messenger RNA (mRNA) molecule, which is not yet present during the initiation stage.

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