Mutations
Objectives
Explain what mutations are
 Contrast gene mutations and
chromosomal mutations

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
Types of Mutations

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
Mutations
Review
Explain what
mutations are

Mutations are changes in the
genetic material
Contrast gene
mutations and
chromosomal
mutations

Gene mutations produce changes
in a single gene
Chromosomal mutations produce
changes in the whole chromosome

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