unit 1 KA6 - mutations Flashcards
what are mutations
changes in the DNA that can result in no protein or an altered protein being synthesized
what are single gene mutations
they involve the alteration of a DNA nucleotide sequence as a result of the substitution, insertion or deletion of nucleotides
what are the three nucleotide substitutions
- missense
- nonsense
- splice-site mutations
describe missense mutations
- they result in one amino acid being changed for another. this may result in a non-functional protein or have little effect on the protein
describe nonsense mutations
they result in a premature stop codon being produced which results in a shorter protein
describe splice-site mutations
they results in some introns being retained and/or some exons not being included in the mature transcript
what do nucleotide insertions or deletions result in
frame-shift mutations
what do frame-shift mutations result in
they cause all of the codons and all of the amino acids after the mutation to be changed. this has a major effect on the structure of the protein produced
what are the four chromosome structure mutations
- duplication
- deletion
- inversion
- translocation
what is a duplication chromosome structure mutation
duplication is where a section of a chromosome is added from its homologous partner
what is a deletion chromosome structure mutation
deletion is where a section of a chromosome is removed
what is an inversion chromosome structure mutation
inversion is where a section of chromosome is reversed
what is a translocation chromosome structure mutation
translocation is where a section of a chromosome is added to a chromosome, not its homologous partner
why are chromosome structure mutations often lethal
because they cause substantial changes
describe the importance of mutations and gene duplication in evolution
duplication allows potential beneficial mutations to occur in a duplicated gene whilst the original gene can still be expressed to produce its protein
