17
Question
Assertion: There is always a time lag between the infection and appearance of AIDS symptoms.
Reason: HIV is a retrovirus.
Assertion: There is always a time lag between the infection and appearance of AIDS symptoms.
Reason: HIV is a retrovirus.
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Solution
The correct option is B Both assertion and reason are correct but reason is not the correct explanation of assertion.
Human Immunodeficiency virus (HIV) attacks and weakens the human immune system. Viruses which have single stranded RNA are known as retrovirus. Since HIV has two single stranded RNA it is a retrovirus.
HIV is characterised with very long incubation periods, i.e, the time between the infection or entry of the virus into the body and the appearance of the first symptom which can vary from a few months to many years (5-10 years).
The HIV inserts its RNA in the host cell and the viral reverse transcriptase enzyme converts the RNA of HIV into viral DNA which integrates into the host genome. This integrated viral DNA remains hidden from the immune system and directs the host cell to form multiple copies of itself.
Initially the rate of viral replication is slow which extends the incubation period as the viral load in the body is not high enough to manifest symptoms of AIDS. Once a large number of helper T cells in the body are destroyed, the symptoms of AIDS are exhibited during the last stage of HIV infection.
The length of the incubation period depends on age of the patient, ability to fight (immunity, the mode of transmission (incubation period is shorter when HIV is transferred from mother to child that when it is transmitted through blood transfusion) and the size of the inoculum (number of viral particles that enter the host).
Thus, both the assertion and reason are correct but reason is not the correct explanation of assertion.
Human Immunodeficiency virus (HIV) attacks and weakens the human immune system. Viruses which have single stranded RNA are known as retrovirus. Since HIV has two single stranded RNA it is a retrovirus.
HIV is characterised with very long incubation periods, i.e, the time between the infection or entry of the virus into the body and the appearance of the first symptom which can vary from a few months to many years (5-10 years).
The HIV inserts its RNA in the host cell and the viral reverse transcriptase enzyme converts the RNA of HIV into viral DNA which integrates into the host genome. This integrated viral DNA remains hidden from the immune system and directs the host cell to form multiple copies of itself.
Initially the rate of viral replication is slow which extends the incubation period as the viral load in the body is not high enough to manifest symptoms of AIDS. Once a large number of helper T cells in the body are destroyed, the symptoms of AIDS are exhibited during the last stage of HIV infection.
The length of the incubation period depends on age of the patient, ability to fight (immunity, the mode of transmission (incubation period is shorter when HIV is transferred from mother to child that when it is transmitted through blood transfusion) and the size of the inoculum (number of viral particles that enter the host).
Thus, both the assertion and reason are correct but reason is not the correct explanation of assertion.
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