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Mutations
Changes in the DNA sequence
Causes of mutations
Errors when the DNA is copied during
replication
 During protein synthesis- when proteins are
constructed
 When the cell is dividing- Mitosis or meiosis
 Sometimes external agents, called
mutagens, can cause mutations to occur


Examples of mutagens include. Radiation, UV
sunlight, and certain chemicals like benzene
Mutations in reproductive cells

Changes in the DNA of egg and sperm
cells
 If
these altered cells become fertilized then the
altered genes of the zygote would become part
of the genetic makeup of that organism

These changes could produce a new trait in
the organism
 It
could result in a protein that does not work
properly and death of the embryo
 OR occasionally it may have a positive effect
making if faster or stronger or better able to
survive
Mutations in body (somatic)cells
These types of mutations would not be
passed on to the offspring
 It may cause problems only for the
individual.

 For
example it may cause cells to divide
uncontrollably resulting in cancer
Types of mutations

I. Point mutations

II. Frameshift Mutations

III. Chromosomal Alterations
I. Point mutations
A change in a single nitrogen base pair in
DNA
 Resulting in a change in a single amino
acid used in building a protein
 It can change the functioning of the protein
 ANALOGY:

 THE
 THE
DOG BIT THE CAT
DOG BIT THE CAR
*Notice that the change in the single letter
changed the meaning of the entire sentence.
II. Frameshift Mutations
A single nitrogen base is lost or added in a
DNA strand
 Every nitrogen base after the deleted or
added base would be out of place
 ANALOGY:

 THE
 THE

DOG BIT THE CAT
DOB ITT HEC AT
These types of mutations are more harmful
because every base after the change is
affected.
III. Chromosomal Alterations
When big pieces of the chromosomes are
altered in some way
 These types of mutations are called
chromosomal mutations
 Usually occur during meiosis when egg
and sperm are being produced
 They fall into four categories

 1.
 2.
 3.
 4.
Deletion
Insertion
Inversion
Translocation
1. DELETIONS

Deletions occur when part of a
chromosome is left out

ABCDEFG
ABCD
2. INSERTIONS
(DUPLICATIONS)

Insertions (duplications) occur after DNA is
replicated when part of one chromosome
breaks off and rejoins onto another part of
the same chromosome so that part of the
chromosome is repeated.

ABCDEFG
ABCDEFDEFG
3. INVERSIONS

Inversions occur when part of a
chromosome breaks off and rejoins in
reverse order.

ABCDEFG
ABCFEDG
Inversions
Inversions
4. Translocation

Translocations occur when part of a
chromosome breaks off and rejoins on
another totally unrelated nonhomologous
chromosome.

ABCDEFG
WXABCDEFG