HIV gene is/are
**Core Concept**
HIV (Human Immunodeficiency Virus) is a lentivirus that primarily targets and destroys CD4+ T lymphocytes, leading to immunocompromise and progression to AIDS (Acquired Immunodeficiency Syndrome). The HIV genome consists of two identical single-stranded RNA molecules, which are reverse-transcribed into double-stranded DNA for integration into the host cell genome.
**Why the Correct Answer is Right**
The correct answer is a combination of two genes: **gag** (group-specific antigen) and **pol** (polymerase). The **gag** gene encodes structural proteins necessary for viral assembly and budding, including p24, p17, and p9. The **pol** gene encodes enzymes essential for viral replication, including reverse transcriptase (RT), integrase (IN), and protease (PR). These genes are crucial for the life cycle of HIV and are targeted by antiretroviral therapies.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because HIV does not contain a **tat** gene, which is a regulatory gene found in the HTLV-1 virus. While **tat** is essential for HTLV-1 replication, it is not a component of the HIV genome.
**Option B:** This option is incorrect because HIV does not contain a **env** gene, which is responsible for encoding the envelope glycoproteins that facilitate viral entry into host cells. However, HIV does contain **env**-related sequences that encode the envelope proteins gp120 and gp41.
**Option C:** This option is incorrect because HIV does not contain a **rev** gene, which is a regulatory gene found in the HTLV-1 virus. **Rev** is essential for HTLV-1 replication by regulating the expression of viral RNAs, but it is not a component of the HIV genome.
**Clinical Pearl / High-Yield Fact**
The HIV genome is highly mutable, with a high error rate during reverse transcription, which contributes to the rapid evolution and development of antiretroviral resistance.
**Correct Answer: B. env**