Which of the following is function of reverse transcriptase in retroviruses?

Question

Accepted Answer

The correct option is 2: It uses viral RNA as a template for DNA synthesis.

The enzyme reverse transcriptase is the defining feature of retroviruses, such as the Human Immunodeficiency Virus (HIV). These viruses carry their genetic information in the form of single-stranded RNA, which goes against the conventional flow of genetic information, known as the Central Dogma (DNA to RNA to Protein). The essential function of reverse transcriptase is to reverse this flow; it acts as an RNA-dependent DNA polymerase. Upon infection, the enzyme uses the viral RNA genome as a template to direct the synthesis of a complementary single-stranded DNA molecule. This is followed by the synthesis of a second complementary DNA strand, resulting in a double-stranded DNA copy, which is then incorporated into the host cell's chromosome.

The incorrect option is 1: It converts host cell RNA into viral DNA.

This option is incorrect because the RNA template used by the reverse transcriptase is the *viral* genomic RNA, which the virus itself carries into the host cell. The host cell does contain various types of its own RNA (like mRNA, rRNA, and tRNA), but the enzyme's specific role is to copy the genetic information encoded within the viral RNA to create a DNA version of the viral genome. The reverse transcriptase does not randomly copy the host cell's RNA molecules.

The incorrect option is 3: It translates viral RNA into proteins.

Translation is the molecular process by which the genetic information carried by messenger RNA (mRNA) is decoded to produce specific proteins. This complex process is not performed by reverse transcriptase. Instead, it is carried out by the host cell's protein-synthesizing machinery, specifically the ribosomes, transfer RNA (tRNA), and various other protein factors. Reverse transcriptase is a nucleic acid polymerase, an enzyme dedicated to synthesizing DNA, not translating RNA into polypeptide chains.

The incorrect option is 4: It hydrolyzes the host cells DNA.

Hydrolyzing DNA means breaking down the DNA molecule into smaller fragments, a degradative function performed by enzymes called nucleases or DNases. Reverse transcriptase, being a polymerase, performs the opposite function: synthesis or polymerization, which is the process of building a new DNA molecule. While reverse transcriptase typically possesses an associated Ribonuclease H (RNase H) activity that degrades the RNA strand from the newly formed RNA-DNA hybrid, its primary and defining role is to synthesize the DNA copy, and it is not responsible for degrading the host cell's chromosomal DNA.