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).