Q. At which stage of HIV infection does one usually show symptoms of AIDS :
(a) Within 15 days of sexual contact with an infected person.
(b) When infective retro-virus enters in host cells.
(c) When HIV damages large number of helper T-lymphocytes.
(d) When the viral DNA is produced by reverse transcription.
Solution : Correct option : C After entering into the body of a person, HIV enters into macrophages, where RNA genome of the virus replicates to produce viral DNA with the help of enzyme reverse transcriptase which gets incorporated into host cell’s DNA and directs the cells to produce virus particles. Macrophages continue to produce viruses. Simultaneously, HIV enters into helper T- lymphocytes, replicates and produce more viruses which are released in blood and they attack other lymphocytes causing repeated decrease in T- lymphocytes. Due to this person starts suffering from infections that could have been otherwise overcome. So the correct option is “when HIV damages large number of helper T- lymphocytes”