Q.80 The first step in the replication of a virus with the reverse transcriptase deals with the synthesis of
(A) complementary strand of RNA
(B) double stranded RNA
(C) complementary strand of DNA
(D) double stranded DNA

The first step in replication of viruses with reverse transcriptase (retroviruses like HIV) is synthesis of complementary strand of DNA from the viral RNA template, making option (C) correct.

Option Analysis

(A) Complementary strand of RNA

Incorrect; reverse transcriptase performs RNA-dependent DNA synthesis, not RNA-dependent RNA synthesis. RNA complementarity would maintain single-stranded RNA without creating the DNA provirus needed for integration.

(B) Double stranded RNA

Incorrect; retroviral replication requires DNA intermediate for host genome integration. Double-stranded RNA occurs in some viruses (Reoviridae) but reverse transcriptase specifically generates DNA from RNA template.​

(C) Complementary strand of DNA

Correct; reverse transcriptase uses viral RNA as template and tRNA primer to synthesize minus-strand DNA (complementary DNA or cDNA). This first step creates strong-stop DNA covering U5/R regions before template switching.

(D) Double stranded DNA

Incorrect; dsDNA forms later after RNase H degrades RNA template, PPT priming of plus-strand DNA, and second strand transfer. First step produces only single-stranded minus DNA.

Reverse Transcriptase Complementary Strand DNA Synthesis

The first step in replication of viruses with reverse transcriptase involves synthesis of complementary strand of DNA from viral genomic RNA. Reverse transcriptase enzyme uses tRNA primer at PBS site to extend minus-strand DNA through U5/R regions of HIV-like retroviruses.

Retrovirus Replication Step-by-Step

1. tRNA primer binds PBS on viral RNA

2. Reverse transcriptase synthesizes complementary DNA (minus strand)​

3. RNase H degrades RNA template

4. PPT primes plus-strand DNA synthesis

5. Strand transfers complete dsDNA provirus