1. 1
Mutations
The process by which the sequence
of base pairs in a DNA molecule is
altered.
What is a mutation?
Any change in DNA
Any abnormal change in genetic material.
Some can be inherited by the next
generation.
Remember that genes are located in DNA!!!
What causes a mutation?
1.) Changes in the environment OR
mutagens
a. ultraviolet radiation
b. pollutants and chemicals
c. tar from tobacco
2.) Errors during replication, transcription,
or translation
Types of mutations
Point mutations
small (but significant) changes, often in
a single nucleotide base.
Deletions
remove information from the gene. A
deletion could be as small as a single base
or as large as the gene itself.
Types of mutations
Insertions
occur when extra DNA is added into an
existing gene.
Frame Shift
when either addition or deletion of one or two
nucleotide bases. When this occurs, the “reading
frame” is changed so that all the codons read
after the mutation are incorrect.
Guess which type of mutation..
Normal:
As the man saw the dog hit the can end it is
As the man saw the doT hit the can end
Point mutation
As the man saw thehit the can end
deletion
2. 2
Guess which type of mutations…
As the man saw the FAT dog hit the can end
insertation
As the man saw the ogh itt hec ane nd it is
frameshift
Disorders that result from mutations
Sickle Cell Anemia
PKU
Cystic Fibrosis
SICKLE CELL ANEMIA
Sickle cell anemia is a hereditary disease
that causes red blood cells to be shaped
like moons.
It is due to a single nucleotide sibstitution.
This results in a single amino acid
substitution in the hemogloblin molecule.
Phenylketonuria (PKU)
Inherited disorder that causes a lack of the
enzyme that metabolizes phenylalanine
(an amino acid).
Results in a build up of phenylalanine and
effect the central nervous system.
CYSTIC FIBROSIS
Affect mucus and sweat glands of the body
and is caused by a defective gene.
Thick mucus is formed in the breathing
passages of the lungs
Predisposes the person to chronic lung
infections
How else do mutations occur?
Errors can occur in the processes of Mitosis or
meiosis
This is NOT hereditary…. Its just a mistake in
procedure!!
This is called NONDISJUNCTION
The chromosomes fail to separate so you get
some homologous chromosomes migration over
together instead of separating.
3. 3
If this happens you get sex cells like this:
sperm cellegg cell
23
chromosomes
24
chromosomes
When the egg and sperm cell come
together ….
You get a baby with 47 chromosomes!
All the homologous chromosomes pair up
and but you get one group of 3!
Example:
Trisomy 21 (Down’s syndrome)
Person will develop ALL cells with 47
chromosomes….they will have 3
chromosome # 21
Where is the extra chromosome?
Edwards Syndrome
It is like they stop developing ….
their brains are not properly developed
certain neurons don't make it all the way to
the outside of the brain but remain in little clusters
throughout the brain.
This means that they will frequently have
problems doing basic, instinctive, functions like
sucking, swallowing, and breathing.
holes in the heart that don't close
openings in the back (spina bifida) and
stomach (omphalocele)
organs that are not properly formed.
Additionally, Trisomy 18 babies are usually
small, as if they stopped developing and
growing about the 7th month in utero.
