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 2 in the diagram?
choose 1 answer.
a pre - mrnas are modified to include only certain exons.
b pre - mrnas are produced by rna polymerase using a template molecule.
c trnas help add amino acids to a growing polypeptide chain.
d rrnas help translate mrnas in the cytosol.

Explanation:

1. Analyze Step 2: Step 2 is Pre - mRNA → mRNA, which is RNA processing (splicing, capping, poly - adenylation). Splicing involves modifying pre - mRNA to include only certain exons (and remove introns).
2. Analyze Option A: Option A describes alternative splicing, which occurs during RNA processing (Step 2).
3. Analyze Option B: Production of pre - mRNA from DNA is transcription (Step 1), not Step 2.
4. Analyze Option C: Adding amino acids to a polypeptide chain is translation (Step 3), not Step 2.
5. Analyze Option D: Translation (involving rRNA in ribosomes) is Step 3, not Step 2.

Answer:

A. pre - mRNAs are modified to include only certain exons.