Explain how HIV is transmitted, how it multiplies in the body and leads to AIDS, and how AIDS can be prevented.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · Define AIDS and name the virus. AIDS is an immune deficiency acquired during life, caused by HIV, a retrovirus with an RNA genome.
2 · Transmission. Sexual contact, contaminated blood, shared needles, mother to child through the placenta; not by touch.
3 · Replication.
HIV enters macrophages; reverse transcriptase makes viral DNA.
Viral DNA joins host DNA; macrophage becomes an HIV factory.
Virus enters helper T cells; their number falls.
4 · Draw the replication cycle. [Diagram: HIV entering host cell, RNA to DNA by reverse transcriptase, integration, new viruses budding]
5 · Result, diagnosis and treatment. Fever, diarrhoea, weight loss; infections by Mycobacterium, Toxoplasma; time lag 5 to 10 years; ELISA; anti-retroviral drugs only prolong life.
6 · Prevention. Safe blood, disposable syringes, condoms, controlling drug abuse, awareness by NACO, no stigma.
7 · Close in one line. So with no cure available, prevention and awareness are the only protection.
Scoring tip: Name reverse transcriptase and helper T cells, and say HIV does not spread by touch. These three points appear in almost every marking scheme.
