15. Mutations Flashcards
what is the definition of a mutation? why are they important? 3 points
a change in the nucleotide sequence used to store genetic information.
they are importnat because of genetic variation
responsible for many diseases (cancer)
help geneticists understand how biological systems work
where can mutations occur in the gene?
in the protein coding region of a gene and a non coding sequence of a gene
what are the two types of small scale mutations?
base pair subsitutions and insertions/deletions
what are the three types of substition mutations? what do they do?
silent mutatins - no effect on nucleotide because of redundancy
missense- nucleotide mutated into a new one. may have similar properties or not in an important place on the protein sequence
nonsense- changes a nucleotide triplet codon into a stop codon, stops transcription early
what is the type of nucelotide pair insertion/ deletion mutation and what does it do?
frameshift- the insertion or deletion of nucleotides that arent divisable by three, therefore there can be missense (1 nuceleotide pair deletion), nonsense (1 nuceleotide pair insertion) or triplet codon deletion (no frameshift but 3 nuceleotide pairs insertion or deletion)
image will help
when can mutations be induced? 3 points
occur during DNA replication, repair or recombination
DNA polymerase make mistakes in DNA replication
Nucelotide bases sometimes changed their structure and their base pairing properties
what are induced mutation?
mutations that are induced by the enviornment - radiations, chemicals, sunlight
give an example of an induced mutagen
radiation such as in x rays can cause DNA damage. UV radiation causes cross-linking of thymine bases that are adjacent o each other in a DNA strand. this impairs polymerase mevement and must be repaird, mutations occur when mistakes are made during repair
