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MUTATIONS / CANCER
BIOLOGY 12
Mutations and Protein Synthesis
MUTATIONS are any change in the original coding
of DNA, causing a mutation in the gene.
Not all gene mutations are negative. Without genetic
mutations living organisms would not have evolved
over time. Slight mutations are usually beneficial in
order to adapt to an ever changing environment.
Mutations and Protein Synthesis
FRAMESHIFT MUTATIONS occur when a
nucleotide (nitrogenous base) is deleted or one
is substituted which will shift the codons. When
this happens the order of amino acids are
altered changing the final protein.
Mutations and Protein Synthesis
• There are three different types of point
mutations.
1) Silent Mutations – occur when the DNA
code has been changes however the same
amino acid is still placed into the polypeptide
chain. The gene is still expressed as a normal
protein. NO NEGATIVE IMPACT ON PROTEIN.
Mutations and Protein Synthesis
2. Nonsense Mutations: These are when the
mutation results in the addition of a new nucleotide
into the DNA. In the case of sickle cell anemia one
nucleotide is changed which changes the amino acid.
• Some can have very serious effects due to “Frame
shifting” in all the mRNA codons that are down from
the mutation, if there is a deletion or the addition of
a nucleotide.
3. Missence Mutation: These are when a
nucleotide is deleted or added and the result is a
“STOP” or “ NONSENSE CODON, which prevents the
formation of the complete protein.
Sickle Cell Anemia
Gene Control
• The human genome contains hundreds of
thousands of genes.
• These determine all your genetic traits and
control all your biochemistry.
• A mutation can occur during replication
however enzymes are used to check the
bonding between nucleotides to ensure the
correct order has occurred. Considering the
number of times cells reproduce the number
of mutations are minimal.
MUTAGENS
Mutagens are chemicals that cause a mutation
in the sequence of DNA. Some mutagens are:
1.Asbestos
2.X-rays
3.UV radiation
4.Viruses
5.Benzene
6.Microwaves
Cancer
• Cancer is genetic control lost.
• Specifically, cancer is a loss of a cells
ability to control its own rate of mitosis.
• This typically results from a mutation in
the genetic control mechanism.
Cancer
Cancer isn’t a disease in the conventional
sense because:
1. It isn’t caused by a specific pathogen
(although viruses are suspect in some).
2. Cancer isn’t characterized by one set
of symptoms.
• In its simplest sense, cancer is rapid
and uncontrolled cell growth.
Cancer
• The problem is that because these cells
are reproducing so rapidly ( up to once
every 3 hr,), they do not have a chance to
differentiate and become useful.
• They are like embryonic cells.
• Despite being useless, they still must be
fed and provided with the metabolites of
life.
Cancer
• They survive at the expense of normal
cells that do have a function.
• This ultimately can lead to the death of
the individual as so many normal cells
become sacrificed to satisfy the
voracious appetite of the cancer cells.
Comparing Normal Cells and
Cancerous Cells
Cancer
Characteristics of Cancer Cells
1. They lack differentiation
2. Have abnormal shaped nuclei
3. Lack contact inhibition
4. Don’t stick to each other, often migrate
5. Can stimulate vascularization.
CONTACT INHIBITION
• CONTACT INHIBITION in normal cells results
when two cells grow toward one another they
will stop growing. This is triggered by a
growth factor (hormone) which switches the
cells off.
• CANCEROUS CELLS do not respond to this
hormone and will continue to grow recklessly
eventually taking over normal cells. These
cells are like the “bully on the block”
Stages of Cancer
1) Neoplasia: normal cell becomes
cancerous
2) Anaplasia: growth of disorganized mass
of cells - tumor
3) Angiogenesis (vascularization):
stimulation of new blood vessel growth
into tumor.
4) Metastisis: migration of cancer cells into
circulatory and lymphatic systems
How can we protect ourselves?
 Eat a well balanced diet, avoid fatty foods.
Avoid UV radiation, use sun block.
Protect lungs from harmful chemicals.
Safe sex, avoid multiple partners and early
sexual activity.
Maintain a healthy immune system, rest and
exercise boosts immune response.
Reduce exposure to radiation (microwaves, X-rays)
Early Warning Signs
 1. abnormal bleeding
 2. sores that will not heal
 3. pesistent cough
 4. abnormal discharge of fluids
 5. localized pain
 6. change in mole
 7. dizziness, persistant headache, blurred vision
 8. lump under skin
 9. change in diet, loss of appetite
How Cancer Begins
4 main causes of CANCER
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HEREDITY
VIRUSES
CHEMICALS
RADIATION
Initiation of Cancer
Carcinogenesis:
Carcinogenisis is the formation of cancer
cells due to exposure to certain
carcinogens. These carcinogens are
agents like; chemicals like benzene, or
various forms of radiation like UV rays.
MUTATIONS may activate PROTO-ONCOGENS
or inactivate tumor suppressor genes
Cancer
• A cancerous gene is called an
“oncogene”.
• Expression of these genes cause
• uncontrolled cell growth.
• These can be mutated from normal genes
that control cell growth and cell division
called “proto-oncogenes”.
• A mutation can convert a proto-oncogene
into an oncogene.
Cancer
• This will not necessarily result in cancer.
• To manifest cancer, the protooncogene
may need to be hit repeatedly by a
“promotor”.
• These promotors may be external things
such as environmental irritants (smoke,
chemicals, physical irritation) or internal
thing such as growth hormones or growth
factors.
Cancer
• Therefore, the proto-oncogene is converted
to an oncogene by an initiator but must be
activated to a cancer cell by promotors.
• Learn and know the 7 warning signs of
cancer.
• Viruses have been implicated in certain
cancers due to their ability to introduce
new genes (such as an oncogene) or
mutate a proto-oncogene.
STEPS in CARCINOGENESIS
Normal cells
All normal cells have genes called proto-oncogenes on
chromosomes. Therefore all cells can become cancerous.
Step 1
INITIATION
Step 2
PROMOTION
Step 3
Proto-oncogenes
oncogenes
CARCINOGENESIS
INITIATORS are;
PROMOTORS are;
1. Viruses
2. Chemicals
3. Radiation
1. HP virus
2. benzene, asbestos
3. X-rays, microwaves
UV radiation
Cancer
The Common Cancers
1. Lung Cancer
2. Breast cancer
3. Prostate cancer
4. Uterine (cervical) cancer
5. Colon cancer
6. Skin cancer
Common Cancers
• Melanomas; deadly skin cancers
• Carcinomas; affect epithelial tissue
( breast and lung cancer)
• Adenocarcinomas; glandular tissue
( ovarian and pancreatic cancer)
• Sarcomas; affect conncective tissue
( bone cancer)
• Lymphomas; affect lymph tissue
( spleen, certain white blood cells)
• Leukemias; affect leukocytes (white blood cells)
Skin Cancer
Skin Cancer
Colorectal Cancer