Question

question 6 of 10
which action must take place before transcription can begin?
a. trna molecules bring amino acids to a ribosome.
b. rna polymerase unwinds the dna double helix.
c. mrna leaves the nucleus and enters the cytoplasm.
d. polypeptides use mrna to make rna polymerase.

Explanation:

Transcription is the process of synthesizing RNA from a DNA template. For transcription to occur, the DNA double helix must be unwound. RNA polymerase is the enzyme that binds to the DNA and unwinds the double helix at the start of transcription.

• Option A: tRNA bringing amino acids to a ribosome is part of translation (protein synthesis), not transcription.
• Option C: mRNA leaving the nucleus is a step that occurs after transcription (in eukaryotes) when the mRNA is transported for translation.
• Option D: Polypeptides are made during translation, and mRNA is not used to make RNA polymerase in the context of the immediate steps before transcription. RNA polymerase is an enzyme (a protein) that is synthesized through the normal process of gene expression (transcription and translation of the gene encoding RNA polymerase), but that is not the step immediately before transcription of a general gene.

Answer:

B. RNA polymerase unwinds the DNA double helix.