Download Mutation Notes:

Mutation Notes:
Chapter 11
Mutations notes outline
I. Mutation
II. Types at gene level
A. Point
B. Frameshift
which is worse?
III. Types at
chromosome level
A. Deletion
B. Insertion
C. Inversion
D. Translocation
IV. Causes
A. Random/spontaneous
B. Mutagen
V. Results
-, +, no effect
Mutation:
• Mistake or
change in
DNA
sequence
Types of mutations at the gene
level:
• Point:
– change in a SINGLE base
pair in DNA
• Example:
– ACTAGGCAC to
ACTAGTCAC
• Like:
– the dog bit the CAT
to the dog bit the
CAR
– Results in a change of one
codon
• The change in the DNA is minor but
important
The effects of point mutations
Normal
mRNA
Protein
Point
mutation
mRNA
Protein
Frameshift mutations
• A single base is added or deleted from
DNA which shifts the reading of codons by
one base.
ex. ACTAGGCAC to ACTAGAC
Like: The dog bit the cat
to
The dob itt hec at
• The results of frameshift mutations can be
HUGE since every codon after the mistake
is affected!
Frameshift mutations
Without mutation
Frameshift mutation
mRNA
Protein
Deletion of U
Point vs. Frameshift
Mutations
• Which type of mutation is more serious?
– Frameshift mutation affects every amino
acid after the mutation
– Point mutation affects only the amino acid at
the mutation
Chromosomal Alterations
• Chromosomal mutations--Structural changes
in chromosomes
– Are especially common in plants.
• 4 main types— Deletion, insertion, inversion,
translocation
Types of chromosomal
mutations:
• Deletion:
– part of a
chromosome left
out (usually deadly)
A B C D E
A B
F G H
Deletion
C E
F G H
Types of chromosomal
mutations:
• Insertion:
– additions to a
chromosome
– Usually from a
sister chromatid
Insertion
A B C D E
F G H
A B C B C D E
F G H
Insertion
*Genes B and C were inserted into
the chromosome*
Types of chromosomal
mutations:
• Inversion:
– chromosome
part breaks off
and reattaches
backwards
A D C B E FGH
A B C D E F G H
Inversion
Types of chromosomal
mutations:
• Translocation:
– chromosome
part breaks off
and adds to
another
chromosome
Translocation
Causes of Mutations
• Spontaneous/Random mutations–
– Some mutations just happen, (ie. mistake during DNA
replication, transcription, mitosis, meiosis).
• These lead to evolution.
• Mutagen-- Any agent that causes a change in DNA
– Include environmental factors like chemicals and
radiation
– Lead to birth defects if sex cells affected and cancer if
body cells affected
Mutations can be:
• Negative: cause a structural or functional
problem
• Positive (very rare) ex. Can make the
organism faster or stronger
• Have no effect = silent mutation
• Sometimes chromosomes fail to
separate properly and result in
extra or fewer chromosomes:
– Down syndrome- extra
chromosome # 21
– Turner syndrome- missing X on
23rd pair
Inversion
Insertion
Deletion
Translocation