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12–4 Mutations
12-4 Mutations
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12–4 Mutations
12-4 Mutations
Mutations are changes in the genetic
material.
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Kinds of Mutations
Kinds of Mutations
Mutations that produce changes in a single gene
are known as gene mutations.
Mutations that produce changes in whole
chromosomes are known as chromosomal
mutations.
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12–4 Mutations
Kinds of Mutations
Gene Mutations
• A mutation is a change in an organism’s DNA. Many kinds
of mutations can occur, especially during replication.
• Point mutations occur at a single point in the DNA
sequence and include:
1. Substitution
2. Deletion
3. Insertion
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• A substitution mutation
replaces one
nucleotide for another.
Substitutions usually
affect no more than a
single amino acid.
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Kinds of Mutations
• The effects of insertions or deletions are more
dramatic.
• The addition or deletion of a nucleotide causes a
shift in the grouping of codons, therefore, these
mutations are also called frameshift mutations.
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Kinds of Mutations
In an insertion, an
extra base is inserted
into a base sequence.
This extra base
causes the frame to be
shifted.
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Kinds of Mutations
In a deletion, the loss of a single base is deleted and
the reading frame is shifted.
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Kinds of Mutations
Chromosomal Mutations
Chromosomal mutations involve changes in the
number or structure of chromosomes.
Chromosomal mutations include deletions,
duplications, inversions, and translocations.
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Kinds of Mutations
Deletions involve the loss of all or part of a
chromosome.
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Kinds of Mutations
Duplications produce extra copies of parts of a
chromosome.
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12–4 Mutations
Kinds of Mutations
Inversions reverse the direction of parts of
chromosomes.
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12–4 Mutations
Kinds of Mutations
Translocations occurs when part of one
chromosome breaks off and attaches to another.
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Significance of Mutations
Significance of Mutations
Many mutations have little or no effect on gene expression.
If they have no effect, they are referred to as silent.
•A point mutation may not change the amino acid that it is
coded for.
•Even if a change occurs, it may be not be significant
enough to influence protein structure.
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Significance of Mutations
Significance of Mutations
Some mutations change phenotype and are the cause of
genetic disorders. Potential impacts include:
•A mutation may cause a premature stop codon.
•A mutation may change protein shape or the active site.
•A mutation may change gene regulation.
•Polyploidy is the condition in which an organism has extra
sets of chromosomes.
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Significance of Mutations
Significance of Mutations
•Mutations in body cells do not affect offspring.
•Mutations in sex cells can be harmful or beneficial
to offspring.
•Natural selection often removes mutant alleles
from a population when they are less adaptive.
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Mutations can
be caused by
several factors.
Replication errors can
cause mutations.
Mutagens, such as UV
ray and chemicals, can
cause mutations.
Some cancer drugs use
mutagenic properties to
kill cancer cells.
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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.
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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.
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A mutation in which a segment of a chromosome
is repeated is called a(an)
a. deletion.
b. inversion.
c. duplication.
d. point mutation.
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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.
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When two different chromosomes exchange
some of their material, the mutation is called
a(an)
a. inversion.
b. deletion.
c. substitution.
d. translocation.
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