types of gene mutations Flashcards
what is a gene mutation ?
- the alteration of a base in the sequence of bases for one gene
when do gene mutations most likely occur ?
- spontaneously
- during DNA replication
when does DNA replication occur in the cell cycle ?
- during interphase
how can the frequency of gene mutations occurring be increased ?
- by mutagenic agents
because mutations alter the gene, what can it result in ?
- can result in a different amino acid sequence in the encoded polypeptide
what will happen to the protein if the amino acid sequence changes ?
- when the protein is modified into the tertiary structure
- it will form hydrogen and ionic bonds in different places and fold differently
- this will result in a different 3D shape
if the protein has a different 3D shape than what it is supposed to have
what will the protein be called ?
- a non functioning protein
what can alterations to the genes result in ?
- it can result in mutations that causes cancer
what are the 2 types of mutagenic agents ?
- high energy and ionising radiation
- carcinogens
what do high energy and ionising radiation include ?
-radiation such as
- alpha and beta particles
- x-ray and gamma rays
why is UV light considered a mutagenic agent if it is not ionising radiation ?
- because the radiation is still high enough energy that it can cause damage and disrupt the structure of DNA
what is meant by carcinogens ?
- the term given to chemicals that can alter the structure of DNA and can interfere with transcription
what are examples of carcinogens ? (3)
- tobacco smoke
- mustard gas
- peroxides
what are the 6 different types of gene mutations ?
- addition
- deletion
- substitution
- inversion
- duplication
- translocation
what is an addition mutation ?
- one extra base is being added to the DNA sequence
what is the impact of an addition mutation ? what is this called ?
- all the subsequent codons are altered
- known as frame shift
why can addition mutations be very harmful ?
- because all the altered codons could potentially code for different amino acids
- and result in a very different sequence of amino acids
- resulting in a non-functioning protein
what is meant by a deletion mutation ?
- a deletion of a base in the DNA sequence
what will the deletion mutation cause ?
- cause a frame shift to the left
- could result in a different polypeptide chain
- a non functioning protein
what is meant by a substitution mutation ?
- when one base has been changed for a different base
- but the number of bases remains the same
is there a frame shift in substitution mutation ?
- no
why may a substitution mutation have no impact on the polypeptide chain ?
- due to the genetic code being degenerate
- the new triplet base sequence may still code for the same amino acid and so have no impact on the protein structure
if the substitution mutation had no impact on the polypeptide chain, what do we call this ?
- a silent mutation
what is meant by an inversion mutation ?
- a section of bases detach from the DNA sequence,
- but when they rejoin, they are inverted
- so section of code is back to front
what will an inversion mutation result in ?
- different amino acids being coded for in this region
what is meant by a translocation mutation ?
- a section of bases one one chromosome detaches and attaches onto a different chromosome
what kind of alteration is a translocation mutation ?
- a substantial alteration
what can a translocation mutation have an impact on ?
- can cause significant impacts on gene expression and therefore in the resulting phenotype
what happens to the genetic info during translocation mutation ?
- there is no gain or loss in genetic info
