1. Mutations
12-4
Biology
Ms. Haut

2. Mutations Mutations—changes in the genetic material
Can result from Spontaneous Mutations
Errors in DNA replication or recombination
Mutagens—physical or chemical agents
High-energy radiation (X-rays, UV light)

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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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Kinds of Mutations
Gene Mutations 
Gene mutations involving a change in one or a few nucleotides are known as point mutations because they occur at a single point in the DNA sequence.
Point mutations include substitutions, insertions, and deletions.
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Kinds of Mutations
Substitutions usually affect no more than a single amino acid.
Gene mutations result from changes in a single gene. In a substitution, one base replaces another.
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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.
Changes like these are called frameshift mutations.
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Kinds of Mutations
Frameshift 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.
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Kinds of Mutations
In an insertion, an extra base is inserted into a base sequence.
Gene mutations result from changes in a single gene. In an insertion, an extra base is inserted into a base sequence.
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Kinds of Mutations
In a deletion, the loss of a single base is deleted and the reading frame is shifted.
Gene mutations result from changes in a single gene. The loss of a single letter in a sentence models the effects of the deletion of one base in a DNA sequence.
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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.
Chromosomal mutations involve changes in whole chromosomes.
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Kinds of Mutations
Duplications produce extra copies of parts of a chromosome.
Chromosomal mutations involve changes in whole chromosomes.
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Kinds of Mutations
Inversions reverse the direction of parts of chromosomes.
Chromosomal mutations involve changes in whole chromosomes.
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Kinds of Mutations
Translocations occurs when part of one chromosome breaks off and attaches to another.
Chromosomal mutations involve changes in whole chromosomes.
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15. Significance of Mutations
Many mutations have little or no effect on gene expression.
Some mutations are the cause of genetic disorders.
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16. Sickle-Cell Disease
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings

17. Are all Mutations Bad? Although mutations are often harmful,
They are the source of the rich diversity of genes in the living world.
They contribute to the process of evolution by natural selection.

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Are all Mutations Bad?
Beneficial mutations may produce proteins with new or altered activities that can be useful.
Polyploidy is the condition in which an organism has extra sets of chromosomes.
Occurs mostly in plants
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A mutation in which all or part of a chromosome is lost is called a(an)
duplication.
deletion.
inversion.
point mutation.
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A mutation that affects every amino acid following an insertion or deletion is called a(an)
frameshift mutation.
point mutation.
chromosomal mutation.
inversion.
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A mutation in which a segment of a chromosome is repeated is called a(an)
deletion.
inversion.
duplication.
point mutation.
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The type of point mutation that usually affects only a single amino acid is called
a deletion.
a frameshift mutation.
an insertion.
a substitution.
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When two different chromosomes exchange some of their material, the mutation is called a(an)
inversion.
deletion.
substitution.
translocation.
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