Download Mutations

presented by :
Erin Awad Sharkawy
-Mutations are the ULTIMATE source for GENETIC
DIVERSITY!!!
-Mutations are changes in genetic material – changes in
DNA code – thus a change in a gene(s).
-Mutations occurs at a frequency of about 1 in every 1
billion base pairs
-Everybody has about 6 mutations in each cell in their
body!
1- unpaired damage of DNA.
2-errors in the process of replication.
3-insertion or deletion of segments of DNA.
4-spontaneous mutation:
(toutomerism - depurination – deamination ).
5-induced mutation caused by mutagens .
- something that causes the DNA code to
change (mutate).
Physical
Radiation X-ray
U.V•
chemical
Ethidium •
bromide
polyacrylamide •
aflatoxin •
environmental
Viruses •
Abestoses. •
Where mutation happens?
1-May occur in somatic cells (aren’t passed
to offspring), Some type of skin cancers
and leukemia result from somatic
mutations.
2-May occur in germline (eggs & sperm)
and be passed to offspring.
What are the effect s of mutation?
1-Most mutations have no effect on the organism,
because a large portion of the DNA isn’t in genes and
thus does not affect the organism’s phenotype.
2-It may affect the phenotype, the most common effect
of mutations is lethality, because most genes are
necessary for life.
3-Some mutations may improve an organism’s survival
(beneficial and adaptation ).
4-Only a small percentage of mutations causes a visible
but non-lethal change in the phenotype.
Types of mutations:
1-Chromosomal Mutations.
2-Frameshift Mutations.
3-Point Mutations.
May Involve:
-Changing the structure of a
chromosome.
-The loss or gain of part of
a chromosome.
Five types exist:
1- Deletion.
2-Inversion.
3-Duplication.
4-Insertion.
5-Translocation.
6-Nondisjunction
-Failure of chromosomes to separate
during meiosis (1 or 2 ) .
-Causes gamete to have too many or too
few chromosomes
1- Down’s syndrome.
2-Klinefelters syndrome: Due To Presence Of An •
Extra X-chromosome In Male Ie.XXY.
-Change of a single nucleotide Includes the deletion,
insertion, or substitution of ONE nucleotide in a gene.
*These include:
-Missense mutations
-Nonsense mutations
-Silent mutations
Missense mutation:
Change in a single amino acid within a protein.
-This does change in protein.
- Which code for a different AA.
Example:
Normal: THE DOG BIT THE CAT
Mutated: THE DOG BIT THE CAR
Ex :
-Sickle Cell disease is the result
of one nucleotide substitution
Occurs in the hemoglobin gene.
-Only one amino acid changes
in the hemoglobin ( GluVal ).
-The hemoglobin still functions
but it folds differently changing
the shape of the RBCs
( Missense).
Nonsense mutation:
-Nonsense mutations make a premature stop codon that
causing the protein to be shortened.
-Nonsense mutation does change the
resulting protein (code for a stop codon).
Example:
Normal: THE DOG BIT THE CAT
Mutated: THE DOG BIT
Silent mutation:
change the DNA sequence(not the amino acid sequence).
- Silent mutation does not change the resulting
protein and no effect on an organism.
- Code for the same AA .
Example:
Normal: THE DOG BIT THE CAT
Mutated: THE DOG BIT THE KAT
-Inserting or deleting one or more bases
into or from the DNA sequence .
-Changes the “reading frame” like changing
a sentence Proteins built incorrectly and
make it non-functional .
Frameshift Mutations:
Example:
-There are 2 main types of genes that play a role in
cancer are oncogenes and tumor suppressor genes.
1- Oncogenes:
Most oncogenes are mutations of certain normal genes
called proto-oncogenes. Proto-oncogenes are the
"good" genes .When a proto-oncogene mutates
(changes) into an oncogene, it becomes a "bad" gene
that can become permanently turned on or activated.
the cell grows out of control, which can lead to cancer.
a) Inherited mutations of
oncogenes:
b) Acquired mutations of
oncogenes:
For example:
*an inherited mutation in the
gene called RET  this often
develop an uncommon thyroid
cancer called medullary cancer
of the thyroid,
pheochromocytoma and nerve
tumors.
They generally activate
oncogenes by gene
duplication, or mutation.
For example:
*a chromosome
rearrangement can lead to
chronic myeloid leukemia
(CML).
Tumor suppressor genes are normal genes that slow down
cell division, repair DNA mistakes, or tell cells when to die
(a process known as apoptosis or programmed cell death).
When tumor suppressor genes don't work properly,
cells can grow out of control, which can lead to cancer.
Many different tumor suppressor genes have been
found, including TP53 (p53), BRCA1, BRCA2, APC, and RB1.
a) Inherited mutations of tumor
suppressor genes
For example,
a defective APC gene can cause
colon cancer.
b) Acquired mutations of tumor
suppressor genes
Tumor
suppressor
gene
mutations have been found in
many cancers.
For example, abnormalities
of the TP53 gene (which codes
for the p53 protein) have been
found in more than half of
human
cancers.
Acquired
mutations of this gene appear in
a wide range of cancers,
including lung, colorectal, and
breast cancer.