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Gene Mutations
A change in the DNA of a gene is
called a mutation. Mutations in
gametes can be passed on to offspring
of the affected individual, but mutations
in body cells affect only the individual in
which they occur.
Types of Gene Mutations:
1. substitution – one base replaces
another
2. insertion – one or more extra bases
are added
3. deletion – one or more bases are
deleted
Gene Mutations
Base Insertion
Insertions and deletions are called
frameshift mutations because they
shift the “reading frame” of the
genetic content.
For example:
The fat cat ate the hat.
Insertion: The afa tca tat eth eha t.
The fat cat ate the hat.
Deletion: The fat ata tet heh at.
Effects of Mutations
Most mutations have little or no effect, for
example, a substitution may affect only a
single amino acid and usually has no
effect at all.
Insertions and deletions which are
frameshift mutations can change every
amino acid that follows the point of
mutation and therefore can have dramatic
effects on the organism.
Some mutations produce beneficial
variations that allow an organism to better
adapt to its environment.
Genetic material can be altered by:
1. natural or artificial events
2. environmental conditions
3. errors in replication
4. mutagens – chemical or physical
agents in the environment that cause
mutations
Are mutations always harmful?
►No! Some can be beneficial, or have no
effect at all.
►Mutations that are harmful result in the
production of different proteins.
►Mutations in gamete cells are passed on
to offspring, therefore, they are more
significant than a mutation that occurs in
a body cell.
Write the names of the amino acids that
correspond to each mRNA sequence below.
Asp -Try
mRNA sequence: AAU-UGG _____________
Lys -Try
mutation sequence: AAA-UGG _____________
Which type of mutation occurred?
Substitution
_______________
Will the mutation
affect the
organism?
YES
_______________
Write the names of the amino acids that
correspond to each mRNA sequence below.
Cys -Pro
mRNA sequence: UGU-CCG _____________
Cys -Pro
mutation sequence: UGU-CCC _____________
Which type of mutation occurred?
Substitution
_______________
Will the mutation
affect the
organism?
NO
_______________
Write the names of the amino acids that
correspond to each mRNA sequence below.
Val -Leu
mRNA sequence: GUU-UUG _____________
Val -Val
mutation sequence: GUU-GUU-G ___________
Which type of mutation occurred?
Insertion
_______________
Will the mutation
affect the
organism?
YES
_______________
Write the names of the amino acids that
correspond to each mRNA sequence below.
Gly -Ser
mRNA sequence: GGC-UCC _____________
Gly
mutation sequence: GGC_____________
Which type of mutation occurred?
Deletion
_______________
Will the mutation
affect the
organism?
YES
_______________