Question

Read the information for transcription and then answer the question.

Protein Synthesis

Explain the process of transcription.
Transcription is the process by which the information in a DNA sequence is copied into an RNA molecule. It is the first step of gene expression and produces the RNA (mRNA, rRNA, tRNA or other RNAs) that will be used or processed for protein synthesis. Key features and steps:
Check your understanding. Which items did you include? Check all that apply.

The gene coding for the protein untwists and unzips.

RNA nucleotides form complimentary base pairs with the DNA bases.

Hydrogen bonds and sugar-phosphate bonds form and the mRNA strand is synthesized.

mRNA peels off the DNA and moves to the cytoplasm.

Answer 1

All four items apply.

- The gene untwists and unzips: RNA polymerase separates the DNA strands at the promoter so one strand can be used as a template.
- RNA nucleotides form complementary base pairs with the DNA bases: ribonucleotides pair with the DNA template (A–U, T–A, C–G, G–C).
- Hydrogen bonds and sugar–phosphate (phosphodiester) bonds form and the mRNA strand is synthesized: base-pair hydrogen bonds form transiently between template and incoming ribonucleotides, and phosphodiester bonds join the RNA nucleotides into the growing chain.
- mRNA peels off the DNA and moves to the cytoplasm: the completed RNA transcript is released; in eukaryotes it is usually processed (splicing, capping, polyadenylation) and then exported to the cytoplasm for translation (in prokaryotes it can be used immediately).