Mutations Flashcards
What is a mutation?
a change in the arrangement/sequence of bases in an individual gene or in the structure of the chromosome (which changes the arrangement of genes) or extra chromosomes being present
When do mutations occur?
arise spontaneously during DNA replication
What occurs during substitution?
one base has been changed for a different base - only changes one codon and as the degenerate it may still code for the same amino acid so it may not have an impact
What occurs during inversion?
a sequence of bases is reversed (detached from DNA sequence and when they are rejoined they are inverted) - results in different amino scid being coded for in this region
What occurs during deletion?
one or more bases removed from a sequence - causes a frameshift to the left as a different polypeptide chain is produced which may result in a non functioning protein
What occurs during addition?
one or more bases added to a sequence - causes a frameshift as all altered codons could potentially code for different amino acids which redsult in a non functioning protein
What ocurs during translocation?
a sequence of bases is moved from one location in a genome to another - impacts gene expression and resulting phenotype
What do mutagenic agents do?
increase the rate/chance of mutations and increase the chance of one occuring
What are examples of mutagenic agents?
ionising radiation (alpha/beta), high energy radiation (UV- not ionising but high enough to cause damage and disrupt structure of DNA) , chemicals e.g. tar in cigarettes - interferes with transcription
What are the effects of mutations?
can result in different amino acid sequence in the the encoded polypeptide so bonds will form in different places in tertairy structure - protein will fold differently and will be non functioning
How do mutations in chromosomes occur?
arise spontaneously by chromosome non-disjunction in meiosis (when chromosomes don’t split equally during anaphase)
What is polyploidy?
changes in the whole set of chromosomes
What is aneuploidy?
changes in number of individual chromosomes
