All Free Biology MCQs with Answers

2891. The side of sheath attached to head region in bacteriophage is termed as

• A. Capsid
• B. Collar
• C. Core
• D. End plate

Explanation: The collar of a bacteriophage is a structural component that connects the capsid to the tail. It serves as a junction between the head (capsid) containing the viral genetic material and the tail, which is used for attachment to host bacteria and injecting the viral genome into them. The collar is typically made up of protein subunits and may play a role in the phage's ability to recognize and attach to specific bacterial surfaces.

2892. Who purified filterable agents for the first time?

• A. Charles Chamberland
• B. Ivanowski
• C. Louis Pasteur
• D. Stanley

Explanation: Wendell Meredith Stanley was the first to purify a virus, specifically the Tobacco Mosaic Virus (TMV) in 1935. He showed that TMV could be crystallized like a chemical and still remain infectious, which was a major breakthrough. This discovery helped prove that viruses were distinct from other microorganisms and opened the door to modern virology.

2893. Which one of the following sexually transmitted disease attack on T4 Lymphocytes?

• A. AIDS
• B. Genital Herpes
• C. Gonorrhea
• D. Syphilis

Explanation: AIDS (Acquired Immunodeficiency Syndrome) is a serious condition caused by the Human Immunodeficiency Virus (HIV). AIDS is the final stage of HIV infection, where the immune system is severely weakened, making the body highly susceptible to opportunistic infections and certain cancers. While HIV can be managed with treatment, there is currently no cure, making prevention and early intervention critical HIV targets the immune system, specifically attacking CD4+ T cells (helper T cells), which are crucial for immune response.

2894. Which of the following is not true about viruses?

• A. Contain DNA
• B. Can replicate on their own
• C. Can infect bacteria
• D. They have a sub-cellular structure

Explanation: Viruses cannot replicate on their own. They lack the cellular machinery needed for reproduction and must infect a host cell to replicate. Once inside a host cell, a virus hijacks the cell's machinery to produce viral components, which are then assembled into new virus particles. This dependence on a host cell is a defining characteristic of viruses.

2895. The genetic code is bound by a lipid membrane in:

• A. Enterovirus
• B. Hepatitis A virus
• C. Flu virus
• D. Polio virus

Explanation: The flu virus, or influenza virus, is an enveloped virus, meaning its genetic material (RNA) is enclosed within a protective lipid membrane derived from the host cell during viral replication. This lipid membrane, or envelope, contains viral proteins such as hemagglutinin (HA) and neuraminidase (NA), which are crucial for the virus's ability to infect host cells and spread.The lipid envelope helps the virus evade the host immune system and facilitates entry into host cells by fusing with their membranes. However, this envelope also makes the virus more vulnerable to environmental factors like soap and disinfectants, which can disrupt the lipid membrane and inactivate the virus.

2896. Where are the enzymes required for the replication of HIV found?

• A. Surrounding the viral core
• B. Inside the capsid
• C. In the protein spikes
• D. Outside the capsid

Explanation: The enzymes required for HIV replication, such as reverse transcriptase and integrase, are indeed found within the capsid of the virus. The capsid is a protein shell that encases the viral RNA and these essential enzymes. Once HIV enters a host cell, the capsid disassembles, releasing the viral RNA and enzymes, which are necessary for the replication process.

2897. Viruses can not:

• A. Crystallize
• B. Mutate
• C. Excrete
• D. Infect bacteria

Explanation: Viruses do not excrete waste in the same way that living organisms do. They are not considered living cells; instead, they are composed of genetic material (DNA or RNA) enclosed in a protein coat and, in some cases, a lipid envelope. Viruses lack the cellular machinery required for metabolism, including processes like excretion

2898. The conversion of lysogenic cycle to lytic cycle is called:

• A. Conduction
• B. Production
• C. Induction
• D. None of the given options

Explanation: Induction occurs when a dormant virus (prophage) in the lysogenic cycle is activated due to stress factors like UV light or chemicals, leading to its replication and eventual destruction of the host cell.

2899. Symptoms of Hepatitis are:

• A. Loss of immunity
• B. Loss of T helper cells
• C. Blood cancer
• D. None of the given options

Explanation: Hepatitis mainly leads to inflammation of the liver, and this can show up as jaundice, tiredness, and a general feeling of being unwell. These symptoms come from the liver not working as efficiently while it's inflamed.

2900. In binomial nomenclature, the first name refers to the:

• A. Species
• B. Genus
• C. Family
• D. Order

Explanation: The first word in a scientific name refers to the genus, which groups together closely related species.