About Mutation

1. Lesson Overview Mutations

2. Lesson Overview Mutations
MELC
Explain how mutations may
cause changes in the structure
and function of a protein

3. Lesson Overview Mutations
OBJECTIVES
Recognize the effect of mutation
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Describe gene mutation and chromosomal
mutation
Differentiate kinds of mutation

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CHROMOSOMES GENES
LOCATION Inside ________ On __________
NUMBER 23 pairs ___________
SHAPE ____________ Chains of DNA
r e v i e w

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CHROMOSOMES GENES
LOCATION Inside Cell
nucleus
On Chromosomes
NUMBER 23 PAIRS in most
cells
20,000-25,000
SHAPE Cross- shaped
with four arms
Chains of DNA
bases that vary in
length

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Mutations
Now and then cells make mistakes in copying their
own DNA, inserting the wrong base or even
skipping a base as a strand is put together.
These variations are called mutations, from the
Latin word mutare, meaning “to change.”
Mutations are heritable changes in genetic
information.

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Types of Mutations
All mutations fall into two basic categories:
Those that produce changes in a single gene are
known as gene mutations.
Those that produce changes in whole
chromosomes are known as chromosomal
mutations.

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Gene Mutations
Mutations that involve changes in one or a few
nucleotides are known as point mutations
because they occur at a single point in the DNA
sequence. They generally occur during
replication.
If a gene in one cell is altered, the alteration can
be passed on to every cell that develops from the
original one.

12. Lesson Overview Mutations
Gene Mutations
Point mutations include substitutions, insertions,
and deletions.

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Substitutions
In a substitution, one base is changed to a
different base.
Substitutions usually affect no more than a single
amino acid, and sometimes they have no effect
at all.

14. Lesson Overview Mutations
Substitutions
In this example, the base cytosine is replaced by
the base thymine, resulting in a change in the
mRNA codon from CGU (arginine) to CAU
(histidine).
However, a change in the last base of the codon,
from CGU to CGA for example, would still specify
the amino acid arginine.

15. Lesson Overview Mutations
Substitutions

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Deletions and Insertion
Deletions and Insertion are point mutations in
which one base removed then inserted from the
DNA sequence.
If a nucleotide is added or deleted, the bases are
still read in groups of three, but now those
groupings shift in every codon that follows the
mutation.

17. Lesson Overview Mutations
Deletions and Insertion

18. Lesson Overview Mutations
Deletion and Insertion
Deletions and Insertion are also called
frameshift mutations because they shift the
“reading frame” of the genetic message.
Frameshift mutations can change every amino
acid that follows the point of the mutation and can
alter a protein so much that it is unable to
perform its normal functions.

19. Lesson Overview Mutations
Chromosomal Mutations
Chromosomal mutations involve changes in the number
or structure of chromosomes.
These mutations can change the location of genes on
chromosomes and can even change the number of
copies of some genes.
There are four types of chromosomal mutations:
deletion, duplication, inversion, and translocation.

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Chromosomal Mutations

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Chromosomal Mutations
Deletion involves the loss of all or part of a
chromosome. (ex. Cri du chat)

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Chromosomal Mutations
Duplication produces an extra copy of all or part of a
chromosome. (ex. Down Syndrome, Edward
Syndrome)

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Chromosomal Mutations
Inversion reverses the direction of parts of a
chromosome.

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Chromosomal Mutations
Translocation occurs when part of one chromosome
breaks off and attaches to another.

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32. Lesson Overview Mutations
Mutagens
Some mutations arise from mutagens, chemical or
physical agents in the environment.
Chemical mutagens include certain pesticides, a few
natural plant alkaloids, tobacco smoke, and environmental
pollutants.
Physical mutagens include some forms of electromagnetic
radiation, such as X-rays and ultraviolet light.

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34. Lesson Overview Mutations
Harmful and Helpful Mutations
Mutations are often thought of as negative because they disrupt the
normal function of genes.
However, without mutations, organisms cannot evolve, because
mutations are the source of genetic variability in a species.

35. Lesson Overview Mutations
Harmful Effects
Some of the most harmful mutations are those that
dramatically change protein structure or gene activity.
The defective proteins produced by these mutations
can disrupt normal biological activities, and result in
genetic disorders.
Some cancers, for example, are the product of
mutations that cause the uncontrolled growth of cells.

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Harmful Effects
Sickle cell disease is a disorder associated with changes in the
shape of red blood cells. Normal red blood cells are round.
Sickle cells appear long and pointed.
Sickle cell disease is caused by a point mutation in one of the
polypeptides found in hemoglobin, the blood’s principal oxygen-
carrying protein.
Among the symptoms of the disease are anemia, severe pain,
frequent infections, and stunted growth.

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38. Lesson Overview Mutations
Beneficial Effects
Some of the variations produced by mutations can be highly
advantageous to an organism or species.
Mutations often produce proteins with new or altered functions
that can be useful to organisms in different or changing
environments.
For example, mutations have helped many insects resist
chemical pesticides.
Some mutations have enabled microorganisms to adapt to new
chemicals in the environment.

39. Lesson Overview Mutations
Beneficial Effects
Plant and animal breeders often make use of “good”
mutations.
For example, when a complete set of chromosomes
fails to separate during meiosis, the gametes that result
may produce triploid (3N) or tetraploid (4N) organisms.
The condition in which an organism has extra sets of
chromosomes is called polyploidy.

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Beneficial Effects
Polyploid plants are often larger and stronger
than diploid plants.
Important crop plants—including bananas and
limes—have been produced this way.

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A c t i v i t y
In your own words, what is gene mutation?
How about Chromosomal mutation?

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Is mutation beneficial, harmful, or
both? Why?
P r a c t i c a l a p p l i c a t i o n

44. Lesson Overview Mutations
Give a quick summary of Mutation
g e n e r a l i z a t i o n

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A c t i v i t y
Read and Analyze the question/statement. Choose the answer inside
the parenthesis. Write your answer in your activity notebook.
1. ________________ (Deletion, Point Mutation, Mutation,
Inversion) is a genetic mutation in which one base is omitted or
left out; A change to a chromosome in which a fragment of the
chromosome is removed.
2. Mutations that involve changes in one or a few nucleotides are
known as __________ (Mutation, Deletion, Translocation, Point
Mutation) because they occur at a single point in the DNA
sequence.

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3. In a ___________ (Deletion, Inversion, Substitution, Mutation), one
base is changed to a different base.
4. Insertions and deletions are also called ____________ ( Gene
Mutation, Chromosomal Mutation, Frameshift Mutation) because they
shift the “reading frame” of the genetic message.
5. ____________ (Mutation, Gene Mutation, Chromosomal Mutation)
involve changes in the number or structure of chromosomes.
6. (True or False) Because of Mutation genes can vary.

47. Lesson Overview Mutations
For 7- 10, Choose between (deletion, duplication, inversion, and
translocation)
7. _______________ involves the loss of all or part of a
chromosome.
8. ____________ produces an extra copy of all or part of a
chromosome.
9. ____________occurs when part of one chromosome breaks off
and attaches to another.
10. ___________reverses the direction of parts of a chromosome.

48. Lesson Overview Mutations
A c t i v i t y
Read and Analyze the question/statement. Choose the answer inside
the parenthesis. Write your answer in your activity notebook.
1. ________________ (Deletion, Point Mutation, Mutation,
Inversion) is a genetic mutation in which one base is omitted or
left out; A change to a chromosome in which a fragment of the
chromosome is removed.
2. Mutations that involve changes in one or a few nucleotides are
known as __________ (Mutation, Deletion, Translocation,
Point Mutation) because they occur at a single point in the DNA
sequence.
Deletion
Point Mutation

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3. In a ___________ (Deletion, Inversion, Substitution, Mutation), one
base is changed to a different base.
4. Insertions and deletions are also called ____________ ( Gene
Mutation, Chromosomal Mutation, Frameshift Mutation) because they
shift the “reading frame” of the genetic message.
5. ____________ (Mutation, Gene Mutation, Chromosomal Mutation)
involve changes in the number or structure of chromosomes.
6. (True or False) Because of Mutation genes can vary.
Substitution
Frameshift
Mutation
Chromosomal
mutation
True

50. Lesson Overview Mutations
For 7- 10, Choose between (deletion, duplication, inversion, and
translocation)
7. _______________ involves the loss of all or part of a
chromosome.
8. ____________ produces an extra copy of all or part of a
chromosome.
9. ____________occurs when part of one chromosome breaks off
and attaches to another.
10. ___________reverses the direction of parts of a chromosome.
Duplicate
Deletion
Translocation
Inversion