- A gene mutation occurs when there is a change in the sequences in the DNA of a gene. Bases may be added, deleted or substituted. Segments of DNA may be invented or duplicated.
- A mutation produces a change in the DNA codons and is likely to result in a polypeptide with a different amino acid sequence.
- New alleles arise from mutations in existing alleles.
- Mutations in reproductive cells can be passed on to following generations, but mutations in body cells will only affect the tissue in which they occur.
- Mutations occur naturally at random, but the rate of mutation is increased by mutations such as radiationand some organic chemicals.
- The rate of cell division is controlled by proto-oncogenes that stimulate cell division and tumour-supressor genes that slow cell division.
- A mutated proto-oncogene, called an oncogene, stimulates cells to divide too quickly. A mutated tumour-suppressor gene is inactivated, allowing the rate of cell division to increase.
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