Download 12-4 Mutations

DNA & RNA
Mutations
Foothill High School Science Department
Mutations
Key Concept:
Gene mutations result from
changes in a single gene.
Chromosomal mutations
involve changes in whole
chromosomes
Foothill High School Science Department
Gene Mutations
• Point Mutations
– Affect one nucleotide
– Occur at a single point in the
gene sequence
– Three Types:
1. Deletion
2. Insertion
3. Substitution
Foothill High School Science Department
Point Mutations
Frameshift Mutations
Result From
Insertions & Deletions
A nucleotide is added, or subtracted from
the nucleotide sequence. This shifts the
Codon grouping and drastically alters the
amino acid sequence in the protein.
Foothill High School Science Department
Frameshift - Insertion
T
H
T
H
E
C
A
A
T
T
E
T
H
E
R
A
T
A
T
X
E
C
X
A
T
A
T
E
T
H
E
Foothill High School Science Department
R
Frameshift - Deletion
T
H
E
C
x
A
T
A
T
E
T
H
E
R
A
T
H
E
C
T
A
T
E
T
H
E
R
A
T
Foothill High School Science Department
T
Point Mutations
Substitution
A single nucleotide is changed in the
nucleotide sequence.
• This may result in a change to a
single amino acid in the protein.
• The change to a single amino acid
may or may not alter the proteins
function.
Foothill High School Science Department
Point Mutations - Substitution
Codon
=
Amino Acid
UGU
UGC
UGG
UGA
Original
Cysteine
No
Change
Cysteine
Single
AA
Tryptophan
Bad
STOP
Point Mutation - Substitution
T
H
E
x
C
A
T
T
H
E
H
A
T
A
A
T
T
E
E
T
H
E
R
A
T
T
H
E
R
A
T
Foothill High School Science Department
Chromosomal Mutations
• Changes the number or
structure of chromosomes
• May change locations of genes
on chromosome or the number
of copies of some genes
Foothill High School Science Department
Chromosomal Mutations
4 Types
1. Deletion
2. Duplication
3. Inversion
4. Translocation
Foothill High School Science Department
Deletion
X
Deletion
Loss of all or part of a chromosome
Foothill High School Science Department
Duplication
Duplication
Segment of chromosome is
repeated
Foothill High School Science Department
Inversion
Inversion
Chromosome or part of a
chromosome is oriented in the
reverse direction
Foothill High School Science Department
Translocation
Translocation
Part of one chromosome breaks
off and attaches to another,
nonhomologous chromosome
Foothill High School Science Department