Question

the following diagram represents the flow of genetic information from dna to protein.

step 1 step 2 step 3
dna → pre - mrna → mrna → protein

which of the following describes an event that occurs during step 1 in the diagram?

choose 1 answer:

a mrnas are translated into pre - mrnas in the cytosol.

b pre - mrnas are produced by rna polymerase using a template molecule.

c pre - mrnas are processed to include only certain exons.

d trnas and rrnas are used to add amino acids to a growing polypeptide chain.

Explanation:

• Option A: Translation (to make protein) occurs in the cytosol, and Step 1 is transcription (DNA to pre - mRNA), not mRNA to pre - mRNA. So A is wrong.
• Option B: Step 1 is transcription, where RNA polymerase uses DNA (the template molecule) to synthesize pre - mRNA. This matches the process of transcription.
• Option C: Processing of pre - mRNA (like splicing to include certain exons) is Step 2 (pre - mRNA to mRNA), not Step 1. So C is wrong.
• Option D: Adding amino acids to a polypeptide chain is translation (Step 3, mRNA to protein), not Step 1. So D is wrong.

Answer:

B. pre - mRNAs are produced by RNA polymerase using a template molecule.