LEQ: What can go wrong in this process

10.16

MUTATIONS

A change in the nucleotide sequence of DNA

Ultimate source of genetic diversity

Gene vs. Chromosome

Gene M

utations

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

Gene M

utation

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

Chromosom

e Mutations

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

MUTAGENESIS

The creation of a mutation

Spontaneous mutations – mistakes in replication

Mutagen – chemical, physical, or biological agent causes the mistake