Mutations

Hollywood’s images of
mutation
Mutations
Ectrodactyly
Severe Combined
Immunodeficiency Disorder
(SCID)
Sickle Cell Anemia
Heterochromia iridium
Progeria
Hypertrichosis
What is a mutation?
@A mutation is any change in a cell’s
DNA@
 A mutation can occur in an individual
gene
- results in a single changed protein
- bacterial resistance to antibiotics is
an example of a beneficial gene
mutation

What is a mutation continued

A mutation can occur in a chromosome
- a chromosome contains many genes
- chromosomal mutations affect many
proteins
Examples: Down Syndrome
Edward’s Syndrome
Cri-du-Chat
What Causes Mutations?
Can be caused by mutagens- a physical or
chemical cause of mutation. Examples: UV
light, radiation, drugs, and benzene.
 Mutagens are often also carcinogens –
anything that causes cancer
 Can be natural, random events.
- mutations occur in 1/100,000 DNA
replications
 Mutations do not have to be bad (evolution)

Point Mutations Substitution
@A single nucleotide is altered@. Can
change one amino acid in a protein
 Milk – Mile
 GGACAATCA
GGACCATCA

proline -valine-serine
proline-glycine-serine
Frameshift Mutations

@A nucleotide is either inserted or
deleted from a gene.@
-all of the triplets from the point of
mutation onward will be changed
Frameshift Mutations Insertion

An insertion occurs when a nucleotide is
added to a gene
Example: A nucleotide is inserted
The fat cat ate the rat
The faa tca tat eth era t
-the extra nucleotide shifts all of the
triplets that follow
Frameshift Mutations Deletions

A deletion occurs when a nucleotide is
removed from a gene.
Example: A nucleotide is removed
The fat cat ate the rat
Thf atc ata tet her at
Insertion
 GGACAATCA
proline -valine-serine
Deletion
 GGACAATCA
proline -valine-serine
GCGACAATCA
arginine-cysteine-stop
GGAAATCA
proline-leucine
Chromosomal Mutations

Chromosomal mutations involve changes in the
number or structure of chromosomes.
Chromosomal Mutations

Deletion involves the loss of all or part of a
chromosome.
Chromosomal Mutations

Duplication produces an extra copy of all or
part of a chromosome.
Chromosomal Mutations

Inversion reverses the direction of parts of
a chromosome.
Chromosomal Mutations

Translocation occurs when part of one
chromosome breaks off and attaches to
another.
Harmful and Helpful
Mutations


The effects of mutations on genes vary
widely. Some have little or no effect; and
some produce beneficial variations. Some
negatively disrupt gene function.
@However, without mutations, organisms
cannot evolve@
 Mutations are the source of genetic
variability in a species.
Harmful Effects


Some of the most harmful mutations are
those that dramatically change protein
structure or gene activity causing genetic
disorders.
Some cancers, for example, are the
product of mutations that cause the
uncontrolled growth of cells.
 http://www.pbs.org/wgbh/nova/cancer/grow_
flash.html
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 oxygencarrying protein)
Beneficial Effects

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.
Beneficial Effects

Plant and animal breeders often make use
of “good” mutations.

The condition in which an organism has
extra sets of chromosomes is called
polyploidy.