A change in the nucleotide sequence of DNA Ultimate source of genetic diversity Gene vs. Chromosome

 Base Substitution – replacement of one nucleotide with another, change to final protein is minimal – 1 amino acid or no change at all › Silent mutation – base change codes for the same amino acid › Missense mutation – base change codes for a different amino acid › Nonsense mutation – base change codes for a stop codon

 Frameshift Mutation – insertion or deletion of a nucleotide; changes the reading frame of the mRNA codons; can result in different amino acids from the point of the mutation on; major change to the amino acid sequence of the protein

 Mutations that effect multiple genes › Deletion – loss of part of chromosome › Duplication – doubling of part of a chromosome › Inversion – changing the gene order of a chromosome › Translocation – crossing over between nonhomologous chromosomes › Nondisjunction – failure of homologous chromosomes or sister chromatids to separate during meiosis or mitosis

The creation of a mutation Spontaneous mutations – mistakes in replication Mutagen – chemical, physical, or biological agent causes the mistake