All Free Biology MCQs with Answers

2921. The volume of bacteriophage is about _ of the host.

• A. 1/10
• B. 1/100 times
• C. 1/50
• D. 1/1000

Explanation: Option D is correct. Viruses are very small. The size of the largest virus (Poxvirus) is almost equal to the size of the smallest bacteria. The volume of a bacteriophage is about 1/1000th the volume of its host.

2922. It is true for viruses:

• A. Viruses contain only RNA
• B. Viruses are cellular
• C. Tiny and infectious agent
• D. Independent metabolic activities.

Explanation: Viruses are tiny infectious agents that lack many of the key characteristics of living things. They cannot reproduce on their own, as they must infect a host cell to multiply. They have no metabolism and cannot produce energy or synthesize proteins. Unlike cells, viruses lack cellular structure and consist only of nucleic acids (either DNA or RNA, never both) enclosed in a protein coat. They are the smallest infectious agents, visible only under an electron microscope, and rely entirely on host cells for replication.

2923. Viruses can only survive and reproduce inside a:

• A. Animal cells
• B. Bacterial cells
• C. Living cells
• D. Non-living cells

Explanation: Option C is correct. Viruses are obligate intracellular parasites that can only reproduce inside living cells, whether plant, animal, or bacterial. They are not considered living organisms since they cannot replicate on their own or survive in non-living cells. Instead, they inject their genetic material into a host cell and use its machinery to produce new viruses, which then go on to infect other cells.

2924. The genome of the influenza virus is made up of:

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

Explanation: Option A is correct.Influenza is an RNA enveloped virus. It contains a single standard RNA.Viruses are classified on different bases, such as capsid shape, types of hosts, ts, and genome. Based on the genome, there are categories of viruses such as• Double-stranded viruses: herpesviruses, papillomaviruses, poxvirusesSingle-stranded viruses:parvovirus, circovirus • Double-stranded viruses:Reovirus, rotavirus • Single-stranded viruses: poliovirus, coronavirus, Influenza virus, HIV

2925. Which one is not an RNA virus?

• A. Smallpox virus
• B. Mumps and measles viruses.
• C. Influenza virus
• D. Polio virus

Explanation: Option A is correct. Mumps, measles, influenza, and polio viruses all contain RNA as their genetic material. The poliovirus is a small, non-enveloped RNA virus, while influenza is a small, enveloped RNA virus. Smallpox virus, on the other hand, is a large, enveloped virus with a double-stranded DNA genome.

2926. It is present in all the viruses:

• A. DNA
• B. RNA
• C. Capsid
• D. Envelope

Explanation: The capsid, or the protein coat, is present in all viruses. While not all viruses contain only DNA, nor do all contain only RNA. Not all viruses have a glycoprotein envelope around them.

2927. Which of the following is not an essential part of a virus?

• A. Nucleic acid
• B. Capsid
• C. Envelope
• D. None of these

Explanation: Viruses are acellular infectious agents that consist mainly of nucleic acid and a protein coat, and sometimes an outer envelope. The nucleic acid (either DNA or RNA) is the most essential part, as it carries the genetic instructions needed for replication inside a host cell. The capsid, a protective protein coat surrounding the nucleic acid, is also essential because it safeguards the viral genome from damage and helps in attaching to and penetrating host cells. In contrast, the envelope-a lipid layer derived from the host cell membrane-is not essential, since many viruses can survive and remain infectious without it. While the envelope provides advantages like immune evasion and easier entry into host cells, only the nucleic acid and capsid are universally required for a virus to exist and function.

2928. A capsid, the protective coat of a virus, is made up of subunits known as capsomeres that are _ in nature.

• A. Lipid
• B. RNA
• C. Protein
• D. DNA

Explanation: Capsomeres are protein in nature that makes up the capsid. While DNA and RNA are types of viral genomes.

2929. Among the following, _ enzyme is naturally found in HIV.

• A. DNA polymerase
• B. Reverse transcriptase
• C. RNA polymerase
• D. Ligase

Explanation: Among the options provided, "reverse transcriptase" is the enzyme naturally found in HIV.1. DNA polymerase: DNA polymerase is an enzyme that plays a crucial role in DNA replication and repair. It is not naturally found in HIV.2. Reverse transcriptase: Reverse transcriptase is an enzyme that is naturally found in HIV. It is responsible for the conversion of the virus's RNA genome into DNA, which can then be integrated into the host cell's genome. This process is a critical step in the HIV replication cycle.3. RNA polymerase: RNA polymerase is an enzyme responsible for transcribing DNA into RNA during gene expression. It is not naturally found in HIV.4. Ligase: Ligase is an enzyme involved in the repair and joining of DNA strands. It is not naturally found in HIV.So, among these options, only "reverse transcriptase" is the enzyme naturally found in HIV, and it is a key player in the virus's life cycle.

2930. The genome of a virus is composed of:

• A. DNA
• B. RNA
• C. A and B
• D. Protein

Explanation: It is composed of either RNA or DNA. Most animal viruses have a DNA genome, while most plant viruses have an RNA genome. Protein makes the capsid of viruses.