What are mutations?
Change in sequence of bases in DNA of an organism
Occurs naturally during DNA replication at a rate of roughly 1 in 1million bases copied
What are the causes of mutations?
- Spontaneously occurs during DNA replication, chance increased by ‘mutagens’
- Mutagens are chemical, physical, or biological agents that cause mutations
What are the consequences of mutations?
In body cells:
- No effect, can be harmless
- Damages or kills cells/can make cell cancerous, harms person
- Can be advantageous, increases genetic diversity
If the mutation occurs during meiosis/in a sex cell, will be passed onto next generation
What are the types of mutations?
Insertion, deletion, substitution, inversion
What is insertion?
An extra base being added to the DNA sequence
Results in frameshift - triplets shift along, giving whole new amino acid sequence
What is deletion?
Getting rid of a DNA base
Results in frameshift - triplets shift along, giving whole new amino acid sequence
What is substitution?
Swapping one base with another
Triplet may code for different amino acid, could affect whole sequence
What is inversion?
Swapping the order of DNA bases within the triplet of the sequence
Triplet may code for different amino acid, could affect whole sequence
What are the outcomes of mutations?
- Silent mutation
- Nonsense mutation
- Mis-sense mutation
What is a silent mutation?
Where due to degenerate nature of the genetic code, often a change in bases can still result in same protein
What is a nonsense mutation?
Base changes result in the formation of a stop codon in the middle of the sequence
Stops the production of the protein - doesn’t work as normal
What is a mis-sense mutation?
Base changes makes a different amino acid
Produces different polypeptide, effect depends on original role of protein
What causes sickle cell anaemia?
A substitution of 1 base in 6th triplet of gene that codes for 1 of the haemoglobin polypeptides alters the triplet GAG to GTG
What types of organisms can experience a mutation?
Animals, plants, archaea, bacteria, fungi, protists
Can mutations occur in both DNA and RNA?
Yes
What types of chromosome mutations are there?
- Duplication = chromosomes are multiplied
- Deletion = chromosome is removed
- Inversion = order of chromosomes is swapped
- Translation = Chromosomes are mixed, end up with a section of each chromosome
