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12–4 Mutations
12-4 Mutations
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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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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:
Substitution
Deletion
Insertion
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5. 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.
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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14. 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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15. 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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16. 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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12–4
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12–4
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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12–4
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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12–4
A mutation in which a segment of a chromosome is repeated is called a(an)
deletion.
inversion.
duplication.
point mutation.
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12–4
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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12–4
When two different chromosomes exchange some of their material, the mutation is called a(an)
inversion.
deletion.
substitution.
translocation.
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