All Free Biology MCQs with Answers

2821. Infectious proteins are present in:

• A. Gemini viruses
• B. Prions
• C. Viroids
• D. Satellite viruses

Explanation: This option is correct because Prions are the infectious agents composed of abnormal misfolded proteins that have the ability to induce similar misfolding of normal proteins in the brain.

2822. _ infection is caused by a viroid:

• A. Hepatitis A
• B. Hepatitis D
• C. Mad Cow disease
• D. Mysterious brain infection

Explanation: Hepatitis D (delta hepatitis) is caused by the hepatitis D virus (HDV), which is a unique RNA pathogen often classified with viroids because it is a small, circular RNA agent that requites hepatitis B virus for its replication and expression.

2823. The virus envelope is known as:

• A. Capsid
• B. Virion
• C. Nucleoprotein
• D. Core

Explanation: The capsid is the protein coat that surrounds the genetic material (either DNA or RNA) of a virus. It protects the genetic material and helps the virus attach to and enter host cells. As it is outer covering in most viruses so it is the correct answer.

2824. Viruses possess:

• A. Ribosomes to synthesize protein
• B. Organelle for its vital mechanism
• C. Either DNA or RNA
• D. None of these

Explanation: Viruses possess either DNA or RNA as their genetic material. This genetic material can be single-stranded or double-stranded, depending on the type of virus. The genetic material carries the instructions for the virus's replication and function.

2825. The phenomenon of transcription in the HIV life cycle occurs in:

• A. Nucleus
• B. Cytoplasm
• C. Inside viral capsid
• D. None of these

Explanation: In the nucleus, Reverse transcription occurs, the viral RNA is reverse transcribed into DNA by the reverse transcriptase enzymeIntegration: The DNA is integrated into the DNA of the host cell by the integrase enzyme. Transcription: The integrated DNA is transcribed into RNA by the host cell's DNA polymerase.

2826. Which one of the following is a double-stranded DNA virus?

• A. Poxvirus
• B. Parvovirus
• C. Reovirus
• D. Togavirus

Explanation: Pox viruses are a family of viruses that contain double-stranded DNA. This means that their genetic material is made up of two strands of DNA that are linked together.

2827. Virus that affects the genital organs:

• A. HCV
• B. HSV
• C. HIV
• D. Poxvirus

Explanation: HSV (Harpes simplex virus) particularly HSV-2, is a virus that commonly affects the genital organs. It causes genital herpes, characterized by painful sores or blisters in the genital and anal areas.

2828. Protein of HIV that helps in its fusion with T cells:

• A. gp31
• B. gp120
• C. gp141
• D. gp41

Explanation: gp41 is another viral envelope glycoprotein of HIV. After the initial binding of gp120 to the CD4 receptor. gp41 facilitates the fusion of the viral envelope with the host cell membrane, allowing the viral genome to enter the host cell.

2829. _ is common among all viruses during their infection cycles:

• A. DNA replication in cytoplasm
• B. Translation in cytoplasm
• C. Transcription in nucleus
• D. Reverse transcription in cytoplasm

Explanation: Translation, the process of protein synthesis, generally occurs in the cytoplasm for both prokaryotic and eukaryntic cells, including viral infections. Viral proteins are commonly synthesized in the host cell cytoplasm using the cellular machinery.

2830. Virus attacks and hijacks host's _ to make more virus.

• A. Mitochondria
• B. Nucleus
• C. Ribosomes
• D. Endoplasmic reticulum

Explanation: Viruses often hijack host cell ribosomes for protein synthesis. They use the host's ribosomal machinery to produce viral proteins, which are essential for the assembly of new virus particles.