Q.1 The word Archaeobacteria is derived from Greek language which means:

Explanation: The term "Archaea" originates from the Greek word "archaios," meaning "ancient" or "primitive." Therefore, Archaeobacteria (now commonly referred to as Archaea) signifies "ancient bacteria," highlighting their evolutionary lineage as one of the earliest life forms on Earth.

Q.2 What was the initial understanding of diseases caused by what are now known as viruses, before their true nature was discovered?

Explanation: Early scientists suspected that unseen "poisons" were responsible for diseases that couldn't be explained by bacteria, leading to the term "virus" from the Latin word for "poison."

Q.3 What is a key characteristic that distinguishes viruses from living cells?

Explanation: Viruses are defined as non-cellular infectious particles, meaning they lack the complex cellular machinery found in living organisms and cannot carry out life processes independently.

Q.4 Who designed a filter that could trap bacteria but allowed disease-causing agents, suggesting a smaller pathogen?

Explanation: Charles Chamberland, working with Louis Pasteur, developed a filter in 1884 that was crucial in demonstrating the existence of pathogens smaller than bacteria, as agents causing diseases like rabies could pass through it.

Q.5 What significant contribution did W.M. Stanley make to the understanding of viruses in 1935?

Explanation: In 1935, W.M. Stanley successfully isolated and crystallized the Tobacco Mosaic Virus (TMV), providing physical evidence that viruses were distinct entities, a breakthrough that significantly advanced virology.

Q.6 The cell wall of archaeobacteria lacks:

Explanation: The cell walls of Archaea (formerly Archaeobacteria) are structurally distinct from those of bacteria. Unlike bacteria, which have peptidoglycan in their cell walls, Archaea lack peptidoglycan. Their cell walls are composed of various other materials, such as pseudopeptidoglycan, glycoproteins, or S-layers.

Q.7 Cells of Streptococcus are arranged in a:

Explanation: Streptococcus is a genus of spherical (coccus) bacteria that typically grow in chains, hence the name "strepto" which means twisted chain.

Q.8 Escherichia coli is a:

Explanation: Escherichia coli (E. coli) is a rod-shaped bacterium, and "bacillus" is the term used to describe rod-shaped bacteria.

Q.9 Cell envelope includes all of the following except:

Explanation: The bacterial cell envelope typically consists of the plasma membrane, cell wall, and often an outer capsule. While slime layers can be present, they are generally considered distinct from the core components of the cell envelope (plasma membrane, cell wall, and capsule).

Q.10 If cluster/tuft of flagella is present at one end of bacteria then the arrangement is called as:

Explanation: Lophotrichous describes bacteria with a tuft or cluster of flagella at one end. Peritrichous refers to flagella distributed all over the surface, Monotrichous means a single flagellum at one end, and Amphitrichous means a single flagellum at each end.

Q.11 All of the following are present in bacterial cell except:

Explanation: Bacterial cells are prokaryotic, meaning they lack membrane-bound organelles such as mitochondria, endoplasmic reticulum, and Golgi apparatus. They do have cytoplasm, ribosomes, and a nucleoid region where their genetic material is located.

Q.12 The thickness of cell wall of Gram positive bacteria is:

Explanation: Gram-positive bacteria have a thick peptidoglycan layer in their cell wall, typically ranging from 20 to 80 nanometers in thickness. Gram-negative bacteria have a much thinner peptidoglycan layer.

Q.13 The colour attained by Gram negative bacteria after Gram's staining:

Explanation: Gram-negative bacteria stain pink or red after Gram staining because their thin peptidoglycan layer does not retain the crystal violet stain, and they are counterstained by safranin.

Q.14 All of the following components are present in bacterial cell membrane except:

Explanation: Bacterial cell membranes are primarily composed of phospholipids and proteins. Unlike eukaryotic cell membranes, bacterial membranes generally lack cholesterol, with the exception of Mycoplasma, which incorporates sterols from their host.

Q.15 It protects the bacterial cell from osmotic lysis:

Explanation: The rigid cell wall of bacteria provides structural support and protects the cell from osmotic lysis (bursting) when the cell is in a hypotonic environment, preventing excessive water intake.

Q.16 _____ is responsible for antibiotic resistance in bacteria.

Explanation: Plasmids are small, circular, extrachromosomal DNA molecules found in bacteria that often carry genes for antibiotic resistance. These plasmids can be easily transferred between bacteria, contributing to the spread of resistance.

Q.17 Identify the mis-matched pair from the following options:

Explanation: Flagella are primarily responsible for bacterial motility (movement). While other structures like pili or fimbriae are involved in attachment, flagella's main function is propulsion. Cell wall maintains shape, ribosomes perform translation (protein synthesis), and capsules contribute to the sticky nature and virulence.

Q.18 Which of the following structure is present in both viruses and eukaryotic cells?

Explanation: Both viruses (specifically DNA viruses) and eukaryotic cells contain DNA as their genetic material. Ribosomes, cytochrome, and cytoplasm are cellular components found in eukaryotic cells but are generally absent in viruses.

Q.19 Tobacco mosaic virus was identified by:

Explanation: Dmitri Ivanovsky, in 1892, demonstrated that the agent causing tobacco mosaic disease could pass through filters that retained bacteria, thus identifying the Tobacco Mosaic Virus (TMV) as a filterable agent.

Q.20 When they are outside the living cell, viruses represent:

Explanation: Outside a living host cell, viruses are metabolically inert and do not carry out any life processes. Therefore, they exhibit non-living characteristics in this state.

Q.21 A mature virus contain:

Explanation: Viruses are unique in that their genetic material can be either DNA or RNA, but never both simultaneously within a single virion. This is a fundamental characteristic used in viral classification.

Q.22 Viruses are:

Explanation: Viruses are obligate intracellular parasites, meaning they can only replicate and carry out their life cycle within living host cells, as they lack the necessary cellular machinery for independent metabolism and reproduction.

Q.23 All of the followings are non-living features of viruses except:

Explanation: Mutations are changes in the genetic material, which allow viruses to evolve and adapt. This ability to mutate and evolve is considered a living characteristic, unlike the lack of cellular structure, respiration, or the ability to be crystallized, which are non-living features.

Q.24 The viral genome is surrounded by a protein coat, the:

Explanation: The capsid is the protein shell that encloses the genetic material (DNA or RNA) of a virus. Capsomeres are the individual protein subunits that make up the capsid.

Q.25 In some animal viruses the nucleocapsid is covered by another membrane derived from the host cell, the:

Explanation: Many animal viruses acquire a lipid bilayer membrane, known as an envelope, from the host cell's plasma membrane (or other internal membranes) as they bud off. This envelope often contains viral glycoproteins that aid in host cell recognition and entry.

Q.26 The nucleic acid and capsid are collectively called:

Explanation: The viral nucleic acid (genome) combined with its surrounding protein capsid is collectively referred to as the nucleocapsid. This structure protects the genetic material and is essential for viral replication.

Q.27 In general appearance cubical phages are regular solid or icosahedral having:

Explanation: An icosahedron is a geometric shape with 20 triangular faces, 12 vertices, and 30 edges. Many viruses, including cubical phages, adopt this highly symmetrical structure for their capsids.

Q.28 The HIV is transmitted by:

Explanation: HIV can be transmitted through intimate sexual contact, contact with infected blood (e.g., sharing needles, transfusions), and from an infected mother to her child during pregnancy, childbirth, or breastfeeding.

Q.29 Inner core of viruses is comprised of:

Explanation: The innermost part of a virus, its core, contains the viral genetic material, which can be either DNA or RNA. This genetic material carries the instructions for viral replication.

Q.30 All ssRNA viruses have enzymes which convert their ssRNA genome into:

Explanation: While some ssRNA viruses replicate via an RNA intermediate (dsRNA), retroviruses (a significant group of ssRNA viruses) possess reverse transcriptase, an enzyme that converts their single-stranded RNA genome into a double-stranded DNA copy. This DNA copy is then integrated into the host genome.

Q.31 Accessory structure of a virion is its:

Explanation: The envelope is an outer membrane found in some viruses, derived from the host cell. It's considered an accessory structure because not all viruses possess it, unlike the capsid and genome which are fundamental components of all virions.

Q.32 Viral enzymes are synthesized by:

Explanation: Viruses are obligate intracellular parasites and lack their own protein-synthesizing machinery (ribosomes). Therefore, they rely entirely on the host cell's ribosomes to translate their messenger RNA (mRNA) into viral proteins, including viral enzymes.

Q.33 Viruses can be classified on the basis of their:

Explanation: Viruses are classified based on multiple criteria, including the type of genetic material (DNA or RNA, single or double-stranded), the symmetry of their capsid, the presence or absence of an envelope, and their host range (which organisms they infect).

Q.34 Herpes virus contains Capsomeres in its capsid:

Explanation: Herpesviruses have a characteristic icosahedral capsid composed of 162 capsomeres, which are the protein subunits that make up the capsid shell.

Q.35 Viral envelope has its role in:

Explanation: The glycoproteins embedded in the viral envelope play a crucial role in host recognition by binding to specific receptors on the surface of host cells. This interaction is the first step in viral infection.

Q.36 Viruses are particles:

Explanation: Viruses are primarily composed of nucleic acid (genome) and protein (capsid), making them nucleoproteins. Enveloped viruses also contain lipids and carbohydrates, but the fundamental structure is nucleoprotein.

Q.37 Which of the following process of HIV life cycle is done by reverse transcriptase?

Explanation: Reverse transcriptase is a key enzyme found in retroviruses like HIV. It catalyzes the process of reverse transcription, where the viral RNA genome is used as a template to synthesize a complementary DNA strand.

Q.38 In 1796, first vaccinated an 8 years old boy with material removed from cowpox lesion on the hand of milkmaid:

Explanation: Edward Jenner is widely recognized for his pioneering work in vaccination. In 1796, he successfully inoculated a young boy with cowpox material, leading to immunity against smallpox, a significant medical breakthrough.

Q.39 The filterable agents were first purified in 1935, when Stanley was successful in crystallizing the virus:

Explanation: In 1935, Wendell Stanley successfully isolated and crystallized the Tobacco Mosaic Virus (TMV), demonstrating that viruses could exist as distinct, physical entities, which was a landmark achievement in virology.

Q.40 Viruses range in size from 250 (nm) of poxviruses to the 20 nm of:

Explanation: Parvoviruses are among the smallest known DNA viruses, with a diameter of approximately 18-26 nanometers, making them significantly smaller than poxviruses (around 250 nm).

Q.41 The best-known phages are T phages that infect:

Explanation: T-phages, such as T2, T4, and T6, are well-studied bacteriophages (viruses that infect bacteria) that specifically target and replicate within the bacterium *Escherichia coli*.

Q.42 The tail of bacteriophage releases the enzyme to dissolve a portion of the bacterial cell wall. This enzyme is:

Explanation: Bacteriophages use the enzyme lysozyme, which is located in their tail structure, to degrade the peptidoglycan layer of the bacterial cell wall. This creates a hole through which the viral genetic material can be injected into the host cell.

Q.43 About 25 minutes after initial infection, about _____ new bacteriophages are formed:

Explanation: The burst size, or the number of new virions released from a single infected bacterial cell, for many bacteriophages (like T-even phages infecting E. coli) typically ranges from 100 to 200 particles. So, 200 is a common average.

Q.44 At the time of Louis Pasteur and Robert Koch the word virus was generally referred to as a poison associated with:

Explanation: In the early days of microbiology, before viruses were understood as distinct entities, the term "virus" (from Latin for "poison") was used to describe any infectious agent that caused disease and often led to death, but could not be seen under a light microscope or cultured like bacteria.

Q.45 The word virus is derived from Latin word venome meaning:

Explanation: The Latin word "virus" literally translates to "poison" or "poisonous fluid." This etymology reflects the early understanding of these agents as mysterious, harmful substances.

Q.46 Reverse transcriptase is present in:

Explanation: Reverse transcriptase is an enzyme characteristic of retroviruses, which are a specific family of RNA viruses. This enzyme allows them to synthesize DNA from an RNA template, a process unique to these viruses.

Q.47 The shape of Polio virus is:

Explanation: Poliovirus has an icosahedral capsid, which gives it a roughly spherical appearance. Icosahedral symmetry is common among many non-enveloped viruses.

Q.48 First of all, AIDS was reported in young males, all these were:

Explanation: The initial cases of AIDS reported in the early 1980s predominantly occurred among young homosexual men, leading to early hypotheses about its transmission routes.

Q.49 Cells in _____ system can also be infected by HIV along with helper T lymphocyte:

Explanation: Besides helper T lymphocytes (CD4+ T cells), HIV can also infect other cells, including macrophages and microglia in the central nervous system, leading to neurological complications associated with AIDS.

Q.50 Hepatitis A is transmitted by contact with _____ from infected individuals:

Explanation: Hepatitis A virus (HAV) is primarily transmitted through the fecal-oral route, meaning it spreads when a person ingests food or water contaminated with the feces of an infected person.

Q.51 Viruses of hepatitis are better studied:

Explanation: Hepatitis A, B, and C viruses are the most common and extensively studied types of hepatitis viruses due to their global prevalence and significant public health impact.

Q.52 Virus causing small pox is:

Explanation: The Variola virus, responsible for smallpox, is a large, complex, and enveloped DNA virus belonging to the Poxviridae family.

Q.53 Virus converts normal cell into cancer cells:

Explanation: Certain retroviruses (e.g., Rous sarcoma virus, Human T-lymphotropic virus) are known to be oncogenic, meaning they can transform normal cells into cancerous cells by integrating their genetic material into the host genome and altering gene expression.

Q.54 Genetically engineered vaccine is not available for:

Explanation: While vaccines are available for Hepatitis A (HAV) and Hepatitis B (HBV), and a vaccine for Hepatitis E (HEV) exists in some regions, a widely available and effective genetically engineered vaccine for Hepatitis C (HCV) has been particularly challenging to develop and is not currently available for general use.

Q.55 Mumps and Measles viruses belong to _____ group:

Explanation: Mumps virus and Measles virus are both members of the Paramyxoviridae family, which are enveloped, single-stranded RNA viruses.

Q.56 Viruses are extremely small infectious agents, which can only be seen under:

Explanation: Viruses are sub-microscopic, meaning they are too small to be resolved by conventional light microscopes (like compound or dissecting microscopes). Their visualization requires the much higher magnification and resolution provided by an electron microscope.

Q.57 All viruses are generally resistant to broad range of available antibiotics such as:

Explanation: Antibiotics are drugs designed to target and inhibit the growth of bacteria by interfering with bacterial-specific processes (e.g., cell wall synthesis, bacterial protein synthesis). Since viruses lack these bacterial structures and metabolic pathways, antibiotics are ineffective against them.