BRAINCAKEControl of Gene Expression
Cells control which genes are expressed and how much protein is made. This control can happen at several stages between a gene and its active protein.
1. Before transcription: chromatin structure
DNA in eukaryotes is wound around histone proteins. If the DNA is tightly packed, RNA polymerase cannot reach the gene and it is not transcribed. Chemical changes to DNA and histones, called epigenetic modifications, loosen or tighten the packing.
2. Transcription
Proteins called transcription factors bind to DNA near a gene and either help or prevent RNA polymerase binding to the promoter. This is the main way genes are switched on and off.
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Key terms in this lesson
- second messenger
- A chemical inside a cell that relays a signal from a receptor at the cell surface to target molecules within the cell.
- protein kinase
- An enzyme that adds a phosphate group to another protein, often activating or deactivating it.
More in Gene Expression
- Gene Expression
- Gene Probes
- Transcription Factors
- RNA Splicing
- Epigenetics
- DNA Methylation
- DNA Demethylation
- Euchromatin and Heterochromatin
All 39 lessons in Gene Expression · All Edexcel A-level Biology topics