concept 17.5: mutations of one or a few nucleotides can affect protein structures and function

what is a mutation

a change in the genetic material of a cell or virus that can occur from errors in DNA replication or exposure to mutagens (chemical or radiation)

point mutation

chemical change in just one base pair of a gene

genetic disorder or hereditary disease

when the mutation has an adverse effect on the phenotype of the organism

what are the two different types of point mutations

single nucleotide-pair substitutions and nucleotide- pair insertions or deletions

what occurs in single nucleotide pair substitutions

replaces one nucleotide and its partner with another pair of nucleotides

what occurs in nucleotide-pair insertions or deletions

additions or losses of one or more nucleotide pairs in a gene

what are the three different types of nucleotide- pair substitutions

silent mutations

missense mutations

nonsense mutations

silent mutations

have no effect on the amino acid produced by a codon because of the redundancy in the genetic code (wobble)

missense mutations

altered base pair still codes for an amino acid but not necessarily the right amino acid- most common

nonsense mutation

change an amino acid codon into a stop codon and will almost always lead to a non functional protein

frameshift mutation

when the insertion or deletion of nucleotides alters the reading frame

mutagens

physical or chemical agents that cause mutations

what are some examples of mutagens

high energy radiation, base analogs (chemicals similar to normal DNA bases that cause incorrect base pairing), carcinogens (cancer causing chemicals)