Biology · Rung 3 of 4

Gene expression

Expressing a gene starts with making RNA from DNA: transcription. To make proteins, ribosomes translate information in messenger RNA into an amino acid sequence. Regulation controls what is produced, where and how much, allowing cells with very similar genomes to specialise.

Where this sits

Comes after
DNA & genes
Opens up
Genetic engineering

Exercises from this rung

Generated by the app, from easiest to hardest

  1. Put the path from a gene to its protein in order.

    Answer RNA polymerase copies the gene into messenger RNA, The messenger RNA leaves the nucleus, The ribosome reads the codons three at a time, Transfer RNAs bring each amino acid, The amino acid chain folds and is now a protein

    Why Transcription inside the nucleus, translation outside, at the ribosome. What is striking is what is missing: DNA never leaves the nucleus. It sends out an RNA copy, which gets used up, and so the original stays safe from every protein that is made.

    easier

  2. Making RNA using a DNA strand as a template is called…

    • Fertilisation
    • Translation
    • Transcription

    Why During transcription, an RNA polymerase produces RNA using a DNA sequence. If it is messenger RNA, it can later guide protein synthesis. Copying DNA into DNA is replication, a different process.

    in between

  3. A messenger RNA reads 5'-AUG AUA AAU ACG-3'. What amino acid chain is translated?

    • Met-Ile-Asn-Leu
    • Met-Ile-Asn-Thr
    • Met-Ile-Asn-Arg
    • Thr-Asn-Ile-Met

    Why Met-Ile-Asn-Thr: Met (methionine), Ile (isoleucine), Asn (asparagine), Thr (threonine). It is read three at a time from the AUG, which is always methionine and marks where the frame starts. Starting one base later changes every codon, which is why a single extra or missing base in the gene wrecks the whole protein.

    harder