Free Biodiversity and Variety of Life MCQs with Answers

211. It is believed that all complex animal forms evolved from:

• A. Protista
• B. Poriferans
• C. Coelenterates
• D. Arthropods

Explanation: All the higher eukaryotic kingdoms like animalia, plantae and fungi are thought to be evolved from simple or colonial protists.

212. Viruses may not replicate in:

• A. Blood Plasma
• B. A plant cell
• C. Skin cell
• D. Hepatocytes

Explanation: Viruses are obligate intracellular parasites, meaning they require a host cell's machinery to replicate and produce new viral particles. Blood plasma is the liquid component of blood that does not contain any blood cells, such as red blood cells, white blood cells, or platelets. Since blood plasma lacks the necessary host cells for viral reproduction, viruses cannot replicate in blood plasma.

213. Nucleic acid is the only component of:

• A. Virus
• B. Viroid
• C. Virion
• D. Prion

Explanation: Viroids are small infectious agents that consist only of a single-stranded RNA molecule. Unlike viruses, viroids do not have a protein coat (capsid) or an outer envelope. They are simpler than viruses and contain only nucleic acid (RNA) as their genetic material. Therefore, nucleic acid is the only component of a viroid.

214. It is false for viruses:

• A. Viruses contain both DNA and RNA
• B. No independent metabolic activities
• C. Viruses are non-cellular
• D. Tiny and infectious agent

Explanation: Viruses do not contain both DNA and RNA simultaneously. They can have either DNA or RNA as their genetic material, but not both at the same time. A virus is classified as either a DNA virus (contains DNA) or an RNA virus (contains RNA). For example, the influenza virus is an RNA virus, while the herpes simplex virus is a DNA virus. Some viruses have single-stranded genetic material (either DNA or RNA), while others have double-stranded genetic material. The presence of either DNA or RNA is one of the defining characteristics used to classify viruses into different groups.

215. The component responsible for determination of shape of virus is:

• A. Kind of nucleic acids
• B. Kind of hosts
• C. Protein subunits
• D. Viral envelope

Explanation: The component responsible for the determination of the shape of a virus is the capsid. The capsid is a protein shell that surrounds the viral genome. It is made up of repeating units called capsomeres. The arrangement of the capsomers determines the shape of the virus. The number of capsomeres is also characteristics of a particular virus and gives definite shape to the virion.

216. In prions, information is carried further through:

• A. DNA
• B. Proteins
• C. RNA
• D. Glycoproteins

Explanation: Option B is correct.Prions are misfolded or infectious proteins with the ability to transmit their mis-folded shape onto normal variants of the same protein and information is carried through the conformational change of the prion protein.

217. _capsomeres are present in capsid of herpes virus.

• A. 152
• B. 252
• C. 162
• D. 262

Explanation: Option C is correct. Capsid of viruses is made up of protein subunits known as capsomeres. Number of capsomeres is characteristic of a particular virus. i.e, herpes virus has 162 capsomeres, adenovirus has 252 capsomeres and polio has 32 capsomeres in their capsid.

218. It acts as a template strand for reverse transcriptase:

• A. Viral DNA
• B. Viral RNA
• C. Most DNA
• D. T-lymphocytes

Explanation: Option B is correct.Reverse transcriptase is an enzyme that is essential for HIV replication. Reverse transcriptase responsible for reverse transcription, during which viral genomic RNA is converted into viral dsDNA in cytoplasm of helper T-cells. The following steps take place in the reverse transcription process: 1) Initiation: Reverse transcriptase binds to the HIV RNA genome and recruits a primer, which is a short piece of RNA that is used to start DNA synthesis. 2)Elongation: Reverse transcriptase uses the primer to synthesize a DNA copy of the HIV RNA genome. 3) Termination: Reverse transcriptase terminates DNA synthesis when it reaches a specific sequence in the HIV RNA genome.When a retrovirus infects a cell, its RNA genome is reverse transcribed into DNA by the virus's reverse transcriptase enzyme. This DNA copy can then be integrated into the host cell's genome, where it can be replicated and expressed which act as template.

219. The phenomenon of transcription in HIV life cycle occurs in:

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

Explanation: Option A is correct.In HIV infected helper T-cells, the process of transcription occurs in nucleus while the process of reverse transcription occurs in cytoplasm.The HIV virus undergoes a number of processes in the nucleus, cytoplasm, and viral capsid during its replication cycle.In the nucleus:Reverse transcription: The viral RNA is reverse transcribed into DNA by the reverse transcriptase enzyme.Integration: 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.In the cytoplasm:Translation: The RNA is translated into proteins by the host cell's ribosomes.Protease cleavage: The proteins are cleaved by the protease enzyme into their active forms.Assembly: The viral proteins and RNA assemble into new virions.In the viral capsid:Maturation: The virions are matured by the removal of the proteins that are not needed for infection.Budding: The virions bud from the host cell membrane and are released into the extracellular environment.

220. The major cell infected by the HIV is:

• A. Leukocyte
• B. Monocyte
• C. Helper T-lymphocyte
• D. B-lymphocyte

Explanation: Option C is correct.Here are the definitions of leukocytes, monocytes, helper T-lymphocytes, and B-lymphocytes:Leukocyte: A leukocyte is a type of white blood cell that is involved in the immune system. There are five main types of leukocytes: neutrophils, eosinophils, basophils, monocytes, and lymphocytes.Monocyte: A monocyte is a type of leukocyte that is derived from bone marrow and matures in the blood. Monocytes are phagocytic cells, which means that they can engulf and destroy foreign invaders. Monocytes also produce cytokines, which are proteins that help to regulate the immune response.Helper T-lymphocyte: A helper T-lymphocyte is a type of lymphocyte that helps to coordinate the immune response. Helper T-lymphocytes produce cytokines that activate other immune cells, such as B-lymphocytes and cytotoxic T-lymphocytes. This one is the correct answer as HIV virus attack on helper T- lymphocytes and causes AIDS.B-lymphocyte: A B-lymphocyte is a type of lymphocyte that produces antibodies. Antibodies are proteins that bind to specific antigens, which are foreign substances that the body recognizes as being harmful. B-lymphocytes are activated by helper T-lymphocytes, and they then produce antibodies that help to fight infection.