bf 2: mutations

mutation

change in dna sequence

substitution mutation

single nucleotide is replaced by another

silent mutation

changes a base but does not change the amino acid

missense mutation

changes one base- changes one amino acid in the polypeptide

nonsense mutation

changes base- converts a codon to a stop codon

insertion mutation

one or more nucleotides added to the dna sequence, if not in multiples of 3- causes frameshift mutation

deletion mutation

one or more nucleotides are removed

duplication mutations

section of dna is copied and inserted next to the original, adds an extra amino acid to polypeptide

expansion of nucleotide repeats

repeats of short dna sequences are abnormally increased

splice site mutations

mutation at intron-exon junctions affects mrna splicing

promoter mutations

dna regions where rna polymerase and general transcription factors bind to a start transcription

somatic mutations

occur in body cells, any cells not involved in producing gametes

germline mutations

occur in gamete-producing cells, sperm or egg

somatic

not inherited

germline mutations

inherited, passed to offspring

spontaneous mutations

mutations that occur naturally during normal cellular processes, caused by random errors in dna replication, repair, recombination

induced mutations

mutations that occur as a result of exposure to an external agent that damages dna or interferes with its replication, caused by mutagens

mutagen

physical or chemical agents that increase mutation rate [uv rays]