7.22—Transcription factors and hormone action
- Syllabus
- 2021
- Objective
- 7.22
- Level
- A2
Transcription factors alter gene expression by controlling transcription
A transcription factor is a protein that binds a regulatory DNA sequence and changes whether RNA polymerase can transcribe a gene. Hormone receptors can act as transcription factors when a lipid-soluble hormone enters a cell and binds them.
Changing transcription changes mRNA production, which can change protein amount and therefore cell behaviour. Different cells respond differently because they express different receptors and target genes.
A steroid hormone–receptor complex can enter the nucleus, bind DNA and increase transcription of a target gene; a peptide hormone usually signals through a membrane receptor instead.
A transcription factor does not translate mRNA or guarantee a phenotype. Distinguish receptor location, DNA binding, transcription and downstream protein function.
ConceptA-Level Edexcel Biology A2