BY5.4 Mutations
- Created by: Yazmin Ali
- Created on: 20-06-16 17:36
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Mutations
- a change in the amount, arrnagement or structure of DNA in an organism
- mutation rates are very smal
- they can affect a single gene or a whole chromosome
- most occur in body cells
- only mutattions that occur in gametic formation are passed on
- spontaneous random events provide the source of material for natural selection pressures - evolution
- organisms with a short life cycle have a greater rate of mutations
- the rate is increased by ionising radiaiton and mutagenic chemicals
Mutagens and Mutation rate:
- mutations occur naturally
- the rate increases when exposed to mutagens (e.g. x rays, gamma radiation, UV light, chemicals)
- mutagens that cause cancer are known as carcinogens
- mutagens don't cause mutations
- an increased exposure to mutagens increases the rate of mutations occuring
mutations happen in 2 ways:
- DNA is not copied properly before cell division
- gene mutation
- chromosomes are damaged and break, when they break they would normally repair but they may not repair properly
- chromosome mutaton
Gene mutations:
- a change in the structure of a DNA molecule
- it affects the differnet alleles of a gene
- a gene can mutate but rates vary from gene to gene
- changes in the base pairs within the genes take the form of duplication, insertion, deletio, inversion or substitution os bases
- this results in the formation of a modified polypeptide
How can mutations change in phenotype?
- genetic code made up of specific sequence of nucleotides on DNA molecules
- any change to nucleotides or rearrangement produces incorrect sequences of amino acids for the protein to make
Sickle cell anemia:
- result of substitution in the gene that produces haemoglobin
- replacement of one base in the DNA molecule…
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