Very helpful from school education point of view.

1. CANCER
&
RETROVIRUS

2. CANCER
Canceris one of themost common disease in theworld.
The division of normalcells is precisely controlled. Newcells
are only formed for growth or to replace dead ones.
Cancerous cells justcontinueto divide giving rise to mass of
cells called tumors.
Tumors are of two types:-
• Benign tumor
• Malignant tumor

3. Benign tumor
Non cancerous
They lack ability to invade neighbour tissueor metastasize.
Malignant tumor
Cancerous
 Invade neighbouringtissue
 They may spread to other location in the body through blood,
& wheneverthey get lodged in thebody, they start newtumor.
This property is called metastasis.

4. Causes of Cancer
 Transformationof normal cells into cancerous cells may be
induced by physical, chemical or biological agents.These agents
are calledcarcinogens.
 Ionizingas wellas non ionizingradiations cause DNA damage
leading to transformationof cancerous cells.
 The chemicalcarcinogens present in tobacco smoke is the
major cause of lung cancer.
 Cancercausing viruses called oncogenic viruses have genes
called viral oncogenes.

5. Categories of Cancer
 Carcinoma: Cancerthatbegins in the skin or in tissuesthatline
or cover internalorgans.
 Sarcoma: Cancer thatbegins in bone, cartilage, fat, muscle,
blood vessels, or other connective or supportive tissue.
 Leukemia:Cancerthatstarts in blood-forming tissuesuch as the
bone marrow & causes large numbers of abnormal blood cells to
be produced & enter theblood.
 Lymphoma & myeloma: Cancers thatbegin in the cells of the
immunesystem.

6.  Centralnervous system cancers: Cancers thatbegin in the tissues
of the brain& spinal cord.

7. Cancer detection & diagnosis
 Biopsy:A small tissue is surgically removed& examined
undera microscope for the presence of cancer cells.

8.  Endoscopy: A flexible plastic tubewitha tiny camera on the
end is insertedinto thebody cavities & organs.
 Diagnosticimaging:Radiography, CT (computed
tomography), MRI (magneticresonance imaging) are useful
to detect cancers of internalorgans.
 Blood test:Some tumors release substancescalled tumor
makers, which can be detected in theblood.

9. Treatment of cancer
 Chemotherapy:Chemotherapyis theuse of drugsthat
either kill cancercells orpreventthecells from dividing.

10. Radiationtherapy: Radiationtherapy is theuse of certain
types of high energyradiation to kill cancer cells & shrink
tumors.

11. Biological therapy / Immunotherapy:It is treatmentwith
substances thathelpthe body’s immunesystem fightcancer
or other diseases, or decrease the side effectsof cancer
treatment.
Surgery: Surgical removal of the damaged tissues or organs is
also a treatmentoption for cancer.

12. Retrovirus
• A retrovirus implies thatreplication is backward compared to
thecentral dogma of molecular biology.
• The genomeof a retrovirus is single-strandedRNA.
• Once it infects thecell, the RNA strand is used as templateto
make double-stranded DNA.
• Retrovirus have been linked to cancer & AIDS.
• Retrovirus thatcause tumor include Rocus sarcoma virus &
Mouse mammary tumor virus.
• AIDS is caused by a retrovirus called HIV.

14. Life cycle of Retrovirus

15.  Whenthey infectcells, theirRNA is turned into DNA by
reverse transcriptase.
 This newDNA is thenincorporated into thehost cellgenome
by an integraseenzyme, at which point retroviral DNA is referred
to as aprovirus.
 The host cellthentreats the viral DNA as part of its own
genome.
 Newviral RNAis produced by theinfectedcell.
 Finally,newviruses are produced which can infectother cells.

16. REFENCES
• Wikipedia
• Biology textbook NCERT
• cancer.about.com
• www.medicinenet.com
• dictionary.reference.com