BRAINCAKEOncogenes
Proto-oncogenes are normal genes that stimulate cell division. Many code for growth factors, or for the receptor proteins on the cell-surface membrane that bind growth factors. When a growth factor binds, the receptor triggers a series of reactions that switches on the genes needed for DNA replication and cell division. In a healthy cell, proto-oncogenes are active only when cell division is needed.
An oncogene is a mutated or abnormally activated proto-oncogene. It is permanently switched on, so cells divide uncontrollably and a tumour can form. This can happen in two main ways:
• The receptor protein is permanently activated, so it triggers DNA replication and cell division even when no growth factor is present.
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Key terms in this lesson
- mutation
- A random change in the base sequence of DNA (a gene mutation) or in the structure or number of chromosomes (a chromosome mutation).
- allele
- One of two or more alternative versions of a gene, occupying the same locus on homologous chromosomes.
More in Control of Gene Expression
- DNA Methylation
- Histone Acetylation
- Epigenetics and Disease
- Benign and Malignant Tumours
- Tumour Suppressor Genes
- Abnormal Methylation and Cancer
- Oestrogen and Breast Cancer
- Epigenetic Treatments for Cancer
All 18 lessons in Control of Gene Expression · All AQA A-level Biology topics