In I/GCSE Biology, a mutation is a rare, random change in genetic material that can be inherited. Many mutations are harmful, but some can be beneficial to the organism, such as becoming antibiotic-resistant. If the mutation is harmful, the cell will die and the mutation will be lost. If not, the cell may not die. It may divide into more cells containing the mutant gene.
When an organism dies, the mutation is lost. Only mutations in sex cells or cells that divide to form sex cells can be passed on.
The rate at which gene mutations occur can be increased by mutagens including:
- Exposure to ionising radiation (such as gamma rays, X-rays and ultraviolet rays)
- Chemicals in tobacco such as nitrous oxide and chemicals formed from burnt food
When DNA is replicating, mistakes can be made, resulting a gene mutation that can alter the sequence of bases in a gene. This leads to genetic coding for a wrong protein (3 bases make up a protein). In I/GCSE Biology, some ways include: 👇 👇 👇
- Duplication – the nucleotide is inserted twice (the ‘T’ is duplicated and pushes everything to the right, altering each of the triplet code and resulting in different proteins being made.
- Deletion – the opposite of duplication, in which a nucleotide is missed out, pulling everything to the left (‘T’ gets deleted and the ‘T’ after replaces the deleted ‘T’, leading to everything being shifted left).
Substitution – A different nucleotide is used. This may not be dangerous as the new triplet code may not code for a different amino acids as most amino acids have more than one code. If it does, then there would be an alteration in the functioning of the protein.
Inversion – The sequence of bases in a triplet is reversed. Only one triplet is affected so like substitution, it may or may not result in a different amino acid or altered protein structure.
Note: Translocation which means part of a chromosome is transferred to another chromosome mainly refers to the chromosome mutation but not gene mutation in I/GCSE Biology.
That's the end of the topic!
Drafted by Joey (Biology)
Reference: https://en.wikipedia.org/wiki/Mutation