Mutations
Mutations

Now and then cells make mistakes in
copying their own DNA, inserting an
incorrect base or even skipping a base
as a new strand is put together →
these mistakes are called mutations

mutation – changes in the genetic
material
Kinds of Mutations

What is a gene mutation?
A gene mutation produces a change in a
Single gene.
 What is a chromosomal mutation?
A chromosomal mutation produces changes
in a whole chromosome.
Gene Mutations

Two types of gene mutations are point
mutations and frameshift mutations.

What is a point mutation?
A point mutation occurs when there are
changes in one or a few nucleotides. They
include substitutions, insertions, and deletions.
Point Mutation: Substitution
Starting Sentence
THE FAT CAT ATE THE RAT
If a substitution occurred….
THE FAT CAR ATE THE RAT
Point Mutation: Substitution

Substitutions
usually affect no
more than a single
amino acid.
Gene Mutations
What is a frameshift mutation?
A frameshift mutation (usually caused by
insertions or deletions) shifts the “reading frame”
of the genetic message.
 These mutations may change every amino
acid that follows the point of the mutation
 Frameshift mutations can alter a protein so
much that it is unable to perform its normal
functions

Frameshift Mutation: Deletion
Starting Sentence
THE FAT CAT ATE THE RAT
If a deletion occurred….
THE FAT CAA TET HER AT
Frameshift Mutation: Insertion

In an insertion, an
extra base is
inserted into a base
sequence.
Chromosomal Mutations

The four types of chromosomal
mutations are: deletions, duplications,
inversions, and translocations.
Chromosomal Mutations
Mutation
Description
deletion
Part of the chromosome is lost.
duplication
Extra copies of part of a
chromosome are made.
translocation Part of a chromosome breaks off and
attaches to another chromosome.
inversion
Sections of a chromosome are
reversed.
Deletion
Duplication
Translocation
Inversion
Significance of Mutations

Most mutations are neutral.

What does this mean?
They have little or no effect on the
Expression of genes or the function of the
proteins for which they code.
Significance of Mutations

What is the significance of mutations
to living things?
1. Mutations can be harmful by producing defective
proteins that disrupt normal biological activities.
2. Mutations are a source of genetic variability and
can be beneficial.
Practice
1. Suppose a deletion occurred in the
following strand of DNA deleting the
first G: A G T C A G G T A
How would it change the product of
protein synthesis (how would it
change the amino acid chain that
would be translated from the original
DNA strand)?
Section Quiz
1. A mutation in which all or part of a
chromosome is lost is called a(an)
a. duplication.
b. deletion.
c. inversion.
d. point mutation.
Section Quiz
2. A mutation that affects every amino acid
following an insertion or deletion is called
a(an)
a. frameshift mutation.
b. point mutation.
c. chromosomal mutation.
d. inversion.
Section Quiz
3. A mutation in which a segment of a
chromosome is repeated is called a(an)
a. deletion.
b. inversion.
c. duplication.
d. point mutation.
Section Quiz
4. The type of point mutation that usually
affects only a single amino acid is called
a. a deletion.
b. a frameshift mutation.
c. an insertion.
d. a substitution.
Section Quiz
5. When two different chromosomes
exchange some of their material, the
mutation is called a(an)
a. inversion.
b. deletion.
c. substitution.
d. translocation.