Life cycle of HIV:
- After getting into the body the HIV enters into macrophages or T-helper cells.
- The viral RNA genome replicated to form viral DNA with the enzyme called reverse transcriptase.
- The viral DNA gets incorporated into the host cell’s DNA by an enzyme called integrase, and directs the infected cell s to produce virus particle.
- The macrophage continues to produce virus and acts as HIV factory.
- Virus released from macrophage attack T-helper cells.
- There is progressive reduction in the number of T-helper cells.
- Due to reduction of T-helper cells the person starts suffering from infections of other virus, fungi and even parasites like Toxoplasma.
- The patient becomes immuno deficient and more prone to other disease.
Diagnosis:
- ELISA (enzyme linked Immuno-sorbent assay)
Prevention of AIDS:
- AIDS has no cure, prevention is the best option.
- Safe blood for transfusion
- Use of disposable needles
- Free distribution of condoms.
- Prevention of drug abuse
- Advocating safe sex and promoting regular checkup.
CANCER:
- Uncontrolled cell division leads to production of mass of cell called cancer.
- Cancerous cell lost the property of contact inhibition.
- Cancerous cell just continue to divide giving rise to masses of cell called tumors.
- Benign tumors:
- Normally remain confined to their original location
- Do not spread to other location.
- Cause little damage.
- Malignant tumors:
- Mass of proliferating cells called neoplastic or tumor cells.
- These cells grow very rapidly.
- Invade and damage surrounding tissues.
- These cells actively divide and grow; they also starve the normal cells.
- Cancerous cells escape from the site of origin and moves to distant place by blood, wherever they get lodged make the normal cell cancerous. This property is called metastasis.
Causes of cancer:
- Normal cells transformed into cancerous neoplastic cells by physical, chemical and biological agents. These agents are called carcinogen.
- Physical agents: ionizing radiation like X-rays, gamma rays non-ionizing radiations like UV-rays.
- Chemical agents: Tobacco smoke, sodium azaide, Methyl ethane sulphonate.
- Biological agents:
- Cancer causing viruses called oncogenic viruses have a gene called viral oncogenes, induce transformation of neoplastic cells.
- Cellular oncogenes (c-onc) or proto oncogenes in normal cells, when activated lead to oncogenic transformation of the normal cells.
Cancer detection and diagnosis:
- Biopsy and histopathological study of the tissues
- Radiography like X-rays, CT (computerized tomography)
- MRI (magnetic resonance Imaging).
- Presence of antibodies against cancer-specific antigen.
Tretment of cancer:
- Surgery
- Radiation therapy
- Immunotherapy
- Chemotherapy
- Cryosurgery
- Laser therapy.
- α-interferone a response modifier used to detect the cancer.
CBSE Biology (Chapter Wise) Class XII ( By Mr. Hare Krushna Giri )
Email Id : harekrushnagiri@yahoo.com
