Question

What are retroviruses?

• A. A group of viruses with RNA genome and reverse transcriptase activity
• B. A group of viruses with DNA genome and no reverse transcriptase activity
• C. A group of viruses with DNA genome and reverse transcriptase activity
• D. A group of viruses with RNA genome and no reverse transcriptase activity

Hint:

The prefix "retro-" means backward.
This refers to the "backward" flow of genetic information from RNA to DNA, which is executed by the enzyme reverse transcriptase.

Answer 1

The Correct Option is A

Step 1 : Understanding the Question:
The question asks for the fundamental biological definition and characteristics of retroviruses.
Step 2 : Key Formulas and Approach:
The approach involves identifying the nature of the genetic material (genome) of retroviruses and their unique mechanism of replication inside host cells.
Step 3 : Detailed Explanation:

Viral Genome: Retroviruses belong to a family of enveloped viruses whose genetic material consists of single-stranded RNA molecules.

Reverse Transcription: Unlike standard central dogma processes where DNA is transcribed into RNA, retroviruses carry a unique enzyme called reverse transcriptase.

Once inside a host cell, this enzyme uses the viral RNA template to synthesize a complementary DNA (cDNA) molecule.

This viral DNA is subsequently integrated into the host cell's genome, allowing the virus to replicate and produce more viral particles.

Thus, retroviruses are characterized by having an RNA genome and showing reverse transcriptase activity.

Step 4 : Final Answer:
Therefore, retroviruses are defined as a group of viruses with an RNA genome and reverse transcriptase activity, as described in Option (A).