AQA · A-Level · Biology
Course version: 7402 · Version from Sept 2016
In eukaryotes, transcription of target genes can be stimulated or…
Full specification wording
Regulation of transcription and translation (A-level only): In eukaryotes, transcription of target genes can be stimulated or inhibited when specific transcriptional factors move from the cytoplasm into the nucleus.
A transcriptional factor is a protein that controls whether a particular gene is transcribed.
Checked against the AQA 7402 specification (opens in a new tab) on .
- Point 1 of 7
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A transcriptional factor is a protein that controls whether a particular gene is transcribed. Many are held inactive in the cytoplasm until a signal arrives; once activated they pass through a nuclear pore into the nucleus and bind to a specific base sequence in the promoter region, the stretch of DNA lying just before the gene. The binding site of the factor is complementary in shape to that sequence, so each factor only affects its own target genes. A stimulatory factor helps RNA polymerase attach to the promoter, so transcription begins, mRNA is produced and the polypeptide is made. An inhibitory factor blocks the promoter, so RNA polymerase cannot bind and no mRNA is transcribed. The gene itself is unchanged in every case; only the amount of mRNA changes.
What earns the marks
- The transcriptional factor moving from the cytoplasm into the nucleus, through a nuclear pore.
- RNA polymerase being stimulated or activated, so transcription of the gene occurs.
- The converse, that if the factor does not bind then fewer transcriptional factors are at the promoter and less or no mRNA is transcribed.
- One mark, in a genetic engineering context, for bacteria not having the required transcriptional factors and so being unable to transcribe the gene.
Common mistakes and how to put them right
Writing that the transcriptional factor 'binds to the gene' without ever naming the promoter region.
Describing the factor binding DNA as an active site and an enzyme-substrate complex, which examiners reject in this topic.
Saying the transcriptional factor makes the protein, instead of controlling transcription of mRNA.
Claiming the factor alters the base sequence of the gene, which would be a mutation, not regulation.
Assuming prokaryotes regulate transcription with the same transcriptional factors as eukaryotes.
Exam tips
- Write 'promoter region' every time; 'binds to the DNA' is too vague to gain the binding mark.
- Make the direction explicit - say whether transcription is stimulated or inhibited, and finish with what happens to the amount of mRNA.
- Keep enzyme language out of it: a transcriptional factor has a binding site, not an active site.
Try the lesson
The start of the Regulation of transcription and translation (A-level only): In eukaryotes, transcription of target genes can be stimulated or inhibited when specific transcriptional factors move from the cytoplasm into the nucleus. lesson, made from checked teaching notes for this specification point.
Have a go first
From which part of a eukaryotic cell do specific transcriptional factors move into the nucleus in order to stimulate or inhibit transcription of target genes?
Listen
A transcriptional factor is a protein that controls whether a particular gene is transcribed. Many are held inactive in the cytoplasm until a signal arrives; once activated they pass through a nuclear pore into the nucleus and bind to a specific base sequence in the promoter region, the stretch of DNA lying just before the gene. The binding site of the factor is complementary in shape to that sequence, so each factor only affects its own target genes. A stimulatory factor helps RNA polymerase attach to the promoter, so transcription begins, mRNA is produced and the polypeptide is made. An inhibitory factor blocks the promoter, so RNA polymerase cannot bind and no mRNA is transcribed. The gene itself is unchanged in every case; only the amount of mRNA changes. A strong answer earns marks for these points. the transcriptional factor moving from the cytoplasm into the nucleus, through a nuclear pore. RNA polymerase being stimulated or activated, so transcription of the gene occurs. the converse, that if the factor does not bind then fewer transcriptional factors are at the promoter and less or no mRNA is transcribed. one mark, in a genetic engineering context, for bacteria not having the required transcriptional factors and so being unable to transcribe the gene. Exam tip: Write 'promoter region' every time; 'binds to the DNA' is too vague to gain the binding mark.
Key words
Say what each word means before you turn the card.
transcriptional factors
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promoter region
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nuclear pore
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See every definition
- transcriptional factors
- Proteins that move from the cytoplasm into the nucleus and stimulate or inhibit transcription of target genes.
- promoter region
- The stretch of DNA lying just before the gene, to which a transcriptional factor binds at a specific base sequence.
- nuclear pore
- The structure through which an activated transcriptional factor passes on its way from the cytoplasm into the nucleus.
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