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
Translocation:
◦ 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
