All Free Biology MCQs with Answers

3031. The complete, mature, and infectious particle is known as

• A. Capsid
• B. Virion
• C. Bacteriophage
• D. Nucleus

Explanation: The virion, that is, the complete infectious virus particle, includes a genome comprising one or a few molecules of either DNA or RNA, surrounded by a morphologically defined protein coat, the capsid; the capsid and the enclosed nucleic acid together constitute the nucleocapsid.

3032. A virus is composed of:

• A. Only proteins
• B. Only nucleic acids
• C. Nucleic acid and protein coat
• D. Nucleic acid, protein coat, lipid envelope

Explanation: A virus is not made of proteins alone (a) or nucleic acids alone (b). Its basic structure always includes nucleic acid surrounded by a protein coat, the capsid (c). However, some viruses also possess an outer lipid envelope derived from the host cell membrane, making the most complete answer (d): viruses are composed of nucleic acid, a protein coat, and sometimes a lipid envelope.

3033. What molecule would you not expect to find in a retrovirus?

• A. Adenine
• B. Thymine
• C. Uracil
• D. Guanine

Explanation: Retroviruses (like HIV) have RNA as their genetic material, not DNA.In RNA, the nitrogenous bases areAdenine (A)Uracil (U) -replaces in RNAGuanine (G)Cytosine (C)Thymine (T) is found in DNA, not in RNA.So, in a retrovirus (RNA virus), you would NOT expect to find thymine.

3034. The viral DNA or RNA is protected by:

• A. Capsid
• B. Envelope
• C. Nucleoproteins
• D. Host-derived structures

Explanation: The viral genome can be protected by the capsid, an additional envelope, associated nucleoproteins, or host-derived structures. These strategies help viruses survive in hostile environments and successfully infect host cells.

3035. What is the viral nucleocapsid made up of?

• A. Genome and capsid
• B. Capsid and spikes
• C. Envelope and capsid
• D. Capsomere and genome

Explanation: "Genome and capsid" is correct because the nucleocapsid consists of the viral genome (DNA or RNA) enclosed within a protein shell called the capsid. This structure protects the genetic material and helps in viral assembly.

3036. What type of virus is the poliovirus?

• A. Double-stranded DNA
• B. Single-stranded DNA
• C. Double-stranded RNA
• D. Single-stranded RNA

Explanation: Poliovirus is a single-stranded RNA (ssRNA) virus, specifically positive-sense RNA, meaning its genome can directly act as mRNA for protein synthesis. It does not have DNA or double-stranded RNA, and it is non-enveloped with only a capsid and RNA genome.

3037. Herpes simplex is caused by which virus?

• A. Adenovirus
• B. Pox virus
• C. Influenza virus
• D. Herpes virus

Explanation: Infection with the herpes simplex virus (HSV), known as herpes, is common globally. HSV type 1 (HSV-1) is typically transmitted by oral-to-oral contact and causes infection in or around the mouth (oral herpes), but it can also cause genital herpes. HSV-2 is mainly sexually transmitted and causes genital herpes.

3038. What type of virus is the herpes simplex virus?

• A. DNA-enveloped virus
• B. RNA-enveloped virus
• C. DNA non-enveloped virus
• D. RNA non-enveloped virus

Explanation: Herpes simplex virus (HSV) is a member of the Alphaherpesvirinae subfamily of the Herpesviridae family. HSV is a double-stranded DNA virus that infects a variety of host tissues and is characterized by a lytic and latent cycle.

3039. What is the number of capsomeres found in the herpes virus capsid?

• A. 162
• B. 200
• C. 234
• D. 155

Explanation: Option A: Correct. The herpes virus capsid has 162 capsomeres, which are protein subunits forming the capsid.Option B: Incorrect. The herpes virus does not have 200 capsomeres.Option C: Incorrect. The capsid does not contain 234 capsomeres.Option D: Incorrect. The capsid does not have 155 capsomeres.

3040. The genome of the virus includes:

• A. Deoxyribonucleic acid
• B. Ribonucleic acid
• C. Proteins
• D. Deoxyribonucleic acid or Ribonucleic acids

Explanation: The genome of a virus refers to its complete set of genetic material, which encodes all the information necessary for the virus to replicate and propagate within a host. Depending on the type of virus, this genome can be composed of either DNA or RNA, and it may exist as single-stranded or double-stranded molecules, which can be linear or circular. The viral genome contains genes that direct the production of viral proteins, including structural proteins that form the viral coat and enzymes required for replication. Because viruses lack the cellular machinery to reproduce on their own, the genome also carries instructions to hijack the host cell's machinery to synthesize viral components. The size and complexity of viral genomes vary widely, from a few thousand nucleotides in simple RNA viruses to over a million base pairs in large DNA viruses, reflecting the diversity of strategies viruses use to infect hosts and evade immune defenses.