CGE: Mutations Flashcards
Mutations
Any change to the base (nucleotide sequence) of DNA.
How can the rate of mutations be increased?
By mutagenic agents.
Substitution
One or more bases are swapped for another.
Deletion
One or more bases are removed.
Addition
One or more bases are added.
Duplication
One or more bases are repeated.
Inversion
A sequence of bases is reversed.
Translocation
A sequence of bases is moved from one location in the genome to another. This could be movement within the same chromosome or movement to a different chromosome.
The order of DNA bases in a gene determines what? If a mutation were to occur in this gene what might happen?
Determines the sequence of amino acids in a particular polypeptide. If a mutation occurs, the sequence of amino acids in the polypeptide that gene codes for could change.
What do polypeptides make up?
Proteins
What might a change in amino acid sequence of a polypeptide cause?
A change in the final 3D shape of the protein, which could mean it can’t function properly.
Healthwise, what can mutations cause?
Genetic disorders - eg. cystic fibrosis. Increased likelihood of developing certain cancers.
Genetic disorders
Inherited disorders caused by abnormal genes or chromosomes. Eg. cystic fibrosis.
Give an example of a mutation that might lead to an increased risk of developing cancer.
Mutations of BRCA1 gene can increase the chances of developing breast cancer.
Hereditary mutations
When a gamete containing a mutation for a genetic disorder or type of cancer is fertilised - will be present in fetus formed.
Are all hereditary mutations harmful?
No - some are beneficial and drive evolution.
Silent mutation
Mutation that doesn’t change the order of amino acids.
The degenerate nature of the genetic code means what for amino acids? What does this mean for mutations?
Some amino acids are coded for by more than one DNA triplet, eg. tyrosine = TAT/TAC Means that not all mutations will result in a change to the amino acid sequence of the polypeptide.
What types of mutations often don’t result in a change in amino acid order?
Substitutions. Inversions.
What types of mutations nearly always change the amino acid sequence?
Additions, duplications and deletions.
Why do additions, duplications and deletions nearly always change the amino acid sequence?
- Mutations change the number of bases in DNA code.
- Causes a frameshift in the base triplets that follow.
- Triplet code is read in a different way.
The base triplets that follow on from the mutation are said to be what?
‘Downstream’ of the mutation.
Give examples of mutagenic agents?
Ultraviolet radiation, ionising radiation, some chemicals and some viruses.
How can mutagenic agents increase the rate of mutations?
- Acting as a base - chemicals called base analogs can substitute for a base in DNA replicaiton, changing base sequence.
- Alter bases - some chemicals can delete or alter bases.
- Change the structure of DNA - some types of radiation can change the structure of DNA, causing problems in DNA replication.
How can mutagenic agents increase the rate of mutations by acting as a base?
Chemicals called analogs can substitute for a base during DNA replication, changing the base sequence of the new DNA.
Eg. 5-bromouracil can substitute for thymine. Can pair with guanine instead of adenine causing a substitution mutation.
How can mutagenic agents increase the rate of mutations by altering bases?
Some chemicals can delete or alter bases.
Eg. alkylating agents can add an alkyl group to guanine, which changes the structure so that it pairs with thymine instead of cytosine.
How can mutagenic agents increase the rate of mutations by changing the structure of DNA?
Some types of radiation can change the structure of DNA, which causes problems during DNA replication.
Eg. UV radiation can cause adjacent thymine bases to pair together.
