M6IQ1- Mutations - Coggle Diagram
- mutations can occur spontaneously and randomly; errors in replication, or mutagens.
- environmental agents that cause mutations- exposure to these substances increases their harmful effects.
- the process of inducing a mutation is called mutagenesis.
- any radiation with a shorter wavelength than visible light can be mutagenic.
- ionising radiation: radioactive materials from nuclear reactions, such as radiation from atomic bombs, toxic spills, and in medicine (x-rays, etc). this can remove electrons from atoms, causing mutations.
- ultraviolet (UV) radiation: from sunlight, and also the UV lights in tanning salons.
- chemicals that cause mutations to occur in DNA.
- free radicals are chemically unstable substances in the body that have lost an electron. they try to become more stable by taking electrons from the body. antioxidants protect against this by donating electrons.
- ingested chemicals: alcohol; tar; tobacco smoke; chemicals in diet- especially charred and fatty foods and food additives and preservatives.
- irritants and poisons: organic solvents such as benzene, cleaning products; asbestos, coal tars; pesticides; hair dyes, certain medications
- organisms that cause mutagens to occur.
- viruses reproduce by injecting their genome into a host cell and disrupting the cell's DNA. This can disturb repair mechanisms and lead to mutations.
- the ageing process can lead to mistakes in mitosis becoming more common.
- some chemical reactions in the body can produce free radicals which can damage DNA and cell membranes.
- fungi produce mycotoxins that can be mutagenic to other species.
Naturally Occurring Mutagens
- part of the environment; physical, radiation, biological or chemical.
- radiation: cosmic rays from the sun, radiation from rocks and soil.
- chemical: incomplete burning (bush fires, coal burning), benzene from crude oil and coal.
- bacteria and viruses.
- mistakes in mitosis or meiosis.
Effects of Mutation,
Gene Flow, and Genetic Drift
Effects of Mutation
- Meiosis and fertilisation cause much variation but only from the available gene pool.
- mutations introduce new genes to the gene pool, making variations available for the development of new species.
- when the environment changes, some variations will be more successful and new species can arise.
Effects of Gene Flow
- gene flow occurs when new alleles are added or removed from the gene pool, due to the movement of fertile individuals or gametes.
- this can be caused by migration of individuals from one population to another, and can be influenced by natural selection or random chance.
- gene flow reduces the difference between populations by altering gene frequencies.
Effect of Genetic Drift
- genetic drift occurs when chance events (random- no natural selection) cause unpredictable changes in allele frequencies from one generation to the next.
- examples of random events: natural disasters, accidental death, extreme weather, etc.
- founder effect: few individuals become isolated from larger population and form a new population.
- bottleneck effect: large population suddenly in size.
Coding and Non-Coding
Coding DNA and Mutation
- DNA is transcribed into mRNA and this code is translated to make proteins. this is often known as gene expression.
- if DNA is altered by a mutagen, and that DNA is part of a gene that could code for a protein, then changing the code could alter the activity of the cell.
- this coding DNA is the exons that are kept after transcription. any change in an exon is carried over into errors in protein production.
Non-Coding DNA and Mutation
- non-coding DNA is not involved in gene expression. this DNA is not translated to make proteins. it can be the introns that are removed after transcription or junk DNA that does not code for a protein.
- some non-coding DNA triggers the action of genes that do code for proteins. if this is changed, then genes that are important for polypeptide synthesis may be switched off or on too often.
- mutations in non-coding DNA often have little effect unless the introns get converted into exons.