Types of mutations Mutations are changes in the genetic material There are two basic types of mutations: Gene mutations - mutations that produce changes in a single gene Chromosomal mutations - mutations that produce changes in whole chromosomes

Gene mutations Point mutations: Involves changes in one or a few nucleotides (they occur at a single point in the DNA sequence) They can be: Substitutions Insertions Deletions

Substitutions One base is changed to another Substitutions usually only affect a single amino acid

Insertions and Deletions A base is either inserted or removed from the DNA sequence If a nucleotide is added or deleted, the bases are still read in groups of three, so every codon after is changed These types of mutations cause Frameshift mutations Can cause major changes to the protein, to the point where it can’t perform its normal function

Chromosomal mutations Involve the chromosomal changes in the number or structure of chromosomes Can change the locations of genes on chromosomes, and the number of copies of some genes Four types: Deletions Duplications Inversions Translocations

Duplications and Deletion Duplication (Nondisjunction): The failure of a chromosome to separate from its homologue during meiosis One gamete receives an extra copy of a chromosome and the other lacks it Deletion: Loss of a piece of a chromosome

Translocations and Inversions When a chromosome piece breaks off and reattaches to another, nonhomologous chromosome Inversion: Chromosome segment breaks off and then reattaches in reverse orientation to the same chromosome

Significance of Mutations Most mutations are neutral (they have little or no effect) Mutations that cause dramatic changes in protein structure or gene activity can be very harmful Mutations are a source of genetic variability in a species Polyploidy- a mutation where an organism has an extra set of chromosomes Polyploid plants are often larger and stronger