What is the basic principle of vaccination? How do vaccines prevent microbial infections? Name the organism from which hepatitis-B vaccine is produced.
The principle of vaccination is based on the property of 'memory' of immune system.
In vaccination, a preparation of antigenic proteins or inactivated/live but weakened pathogens is introduced into the body. The antigens generate primary immune response by producing antibodies along with memory B-cells and T-cells.
When the vaccinated person is attacked by the same pathogens, the existing memory B-cells and T-cells recognise the antigen and overwhelm the invaders with massive production of lymphocytes and antibodies.
Hepatitis-B vaccine is produced from yeast.
What is cancer? How is a cancer cell different from the normal cell? How do normal cells attain cancerous nature?
An abnormal and uncontrolled division of cells is termed as cancer. Genes called cellular oncogenes (c-onc) or proto-oncogens present in normal cells when activated under certain conditions lead oncogenic transformation of the normal cells leading cancer.
A cancer cell is different from the normal cell in following ways
| Cancer cell | Normal cell |
|---|---|
| Cancer cells divide in an uncontrolled manner. | Normal cells divide in a controlled manner. |
| The cells do not show contact inhibition. | The cells show contact inhibition. |
| Life span is indefinite. | Life span is definite. |
A person shows strong unusual hypersensitive reactions when exposed to certain substances present in the air. Identify the condition. Name the cells responsible for such reactions. What precaution should be taken to avoid such reactions.
If a person is hypersensitive to certain substance present in the air, he may be allergic to it. Mast cells release certain chemicals, e.g., histamine and serotonin, in response to this substance, that result in allergic reaction.
Precaution taken to prevent such reaction is to avoid the allergens responsible for particular allergy.
For an organ transplant, it is an advantage to have an identical twin. Why?
For an organ transplant, it is an advantage to have an identical twin because the organ will have same surface markers and therefore, the recipient's immune system will not identify it as foreign and will not react against it. In case of different surface markers, the immune system starts a reaction, kills the foreign tissue or rejects it.
What are lifestyle diseases? How are they caused? Name any two such diseases.
Life style disease are caused by specific food habits, work related posture or exposure to harmful radiations or substances, lack of physical exercise, mental stress, etc. e.g., cancer, alcoholism, heart disease, etc.