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Retroviridae Questions and Answers

1.

Which enzyme is responsible for reverse transcription in HIV?

Exam Year(s)

RSMSSB - 2025, RSMSSB Lab Technician - 2025,

Answer: C

The enzyme is reverse transcriptase.

HIV is a retrovirus: its genome is RNA, and it must copy that RNA into DNA before the DNA can be integrated into the host cell's chromosomes. Reverse transcriptase carries out this RNA-to-DNA copying, which is the reverse of normal transcription. Drugs such as zidovudine and nevirapine work by blocking it.

DNA polymerase copies DNA from DNA, and RNA polymerase makes RNA from DNA, which is ordinary transcription. HIV protease cuts the viral polyproteins into working parts during maturation of new virus particles, a later step.

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2.

Which is the primary receptor for HIV entry in to host cells?

Exam Year(s)

RSMSSB - 2025, RSMSSB Lab Technician - 2025,

Answer: B

The primary receptor for HIV entry is the CD4 receptor.

The HIV envelope glycoprotein gp120 first binds the CD4 molecule on helper T cells, macrophages and dendritic cells. This binding changes its shape so that it can then attach to a co-receptor, after which gp41 fuses the viral and cell membranes.

CCR5 and CXCR4 are those co-receptors: necessary, but secondary to CD4, which is why they are not the primary receptor. CD8 marks cytotoxic T cells and is not used by HIV for entry.

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3.

Which one of the following statements regarding HIV is not correct ?

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: B

The statement that is not correct is It is an Oncovirus.

HIV is a retrovirus of the genus Lentivirus (slow viruses), not of the oncogenic retroviruses (the old 'oncovirus' group, such as HTLV-1). It destroys CD4 T cells rather than transforming cells into cancer cells; the cancers seen in AIDS, such as Kaposi's sarcoma, are caused by other viruses taking advantage of the weakened immunity.

The other statements are correct. HIV belongs to the family Retroviridae (printed 'Retroviridale'). It carries reverse transcriptase, which copies its RNA genome into DNA. It is present in body fluids such as blood, semen, vaginal fluid and breast milk, which is how it is transmitted.

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