- A mutation is the change in the genetic material of an organism, usually the DNA. They are spontaneous and random, a result of chance. But rate of mutations can be increased by exposure to environmental factors (mutagens) eg physical factors such as ionising radiation or chemicals such as benzene of formaldehyde.
- A mutation in an allele is the result of a change in the DNA base sequence. Mutations can occur during DNA replication.
Block/Chromosomal mutations
- Mutations that involve whole genes where parts of chromosomes are deleted, repeated or moved. They can remove alleles from the gene pool (deletion of chromosome) or produce different combinations of alleles (translocation).
- Other mutations involve addition or removal of whole chromosomes.
- gene (point) mutations involve changes to bases in a DNA so they occur within a gene. The base sequence changes in DNA producing a new allele.
- A sequence of 3 bases (triplet) in DNA codes for an amino acid which is the building block for proteins. Any changes to the bases in a triplet can change the amino acid made. This changes the protein. The protein might no longer be produced (early termination) or protein produced is non-functional.
- If the protein changed from a point mutation is an enzyme, it may no longer act as a catalyst.
- If a mutation occurs in the body cells (somatic cells), the mutation can't be passed onto offspring. However, if mutations occur in the reproductive cells (gametes) and is not lethal, the mutation can be passed onto offspring and become part of the gene pool.