AIDS
Read the following passage carefully and answer the given questions.
AIDS is caused by the Human Immunodeficiency Virus, which has an envelope enclosing RNA genome. Transmission of HIV infection generally occurs by (a) sexual contact with infected person, (b) transfusion of contaminated blood and blood products, (c) sharing infected needles, as in case of intravenous drug abusers; and (d) from infected mother to her child through placenta. It is important to note that HIV/AIDS is not spread by mere touch or physical contact; it spreads only through body fluids. It is, hence, imperative, for physical and psychological well-being, that they are not isolated from family and society. Infection with HIV or having AIDS is something that should not be hidden – since then, the infection may spread to many more people. HIV/AIDS-infected people need help and sympathy instead of being shunned by society.
In retrovirus lifecycle, the viral DNA is produced by:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Reverse transcriptase
In most living things, information flows from DNA to RNA. A retrovirus has RNA as its genetic material. In the host cell, its RNA is used as a template to make DNA, which is the reverse of the usual flow. The enzyme that does this is called reverse transcriptase. The viral DNA then joins the host cell’s DNA.
(1) DNA polymerase — Incorrect. DNA polymerase makes DNA on a DNA template, as in DNA replication. It does not use RNA as a template.
(2) DNA ligase — Incorrect. DNA ligase joins pieces of DNA together. It does not make new DNA.
(3) Reverse transcriptase — Correct. It makes DNA from an RNA template.
(4) RNA polymerase — Incorrect. RNA polymerase does the opposite. It makes RNA on a DNA template during transcription.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
AIDS – …
Figure 7.6 Replication of retrovirus