MicroBiology MCQs with Answer and Explnation | Chapter 37

Answer: It is a source of growth regulators

While fruit juice and coconut milk do contain micronutrients and can help maintain pH to some extent, their primary benefit in plant tissue culture media lies in their content of growth regulators, specifically cytokinins. These plant hormones are crucial for promoting cell division and shoot regeneration, two key processes in tissue culture.

The other options are incorrect:

• It is a source of micronutrients: While fruit juice and coconut milk do contain some micronutrients, these can be adequately provided through other components of the media. Their primary contribution goes beyond simply micronutrients.
• It is a source of macronutrients: Fruit juice and coconut milk mainly contain sugars and amino acids, which fall under the category of carbohydrates and proteins respectively. Both are macronutrients, but other sources like sucrose and peptone are typically used for this purpose in tissue culture media.
• It helps in maintaining pH of the media: While fruit juice and coconut milk can buffer the pH to some extent, their primary contribution isn’t solely pH maintenance. Other buffering agents are often used in conjunction with them to ensure optimal pH control.

Answer: A plasmid

pUC 18 is a type of plasmid, which is a small, circular, double-stranded DNA molecule. Plasmids like pUC 18 are commonly used in molecular biology as vectors for cloning and expressing genes.

The other options are incorrect:

• Phage used as a vector: Phages (bacteriophages) are viruses that infect bacteria. While phages can be used as vectors in some applications, pUC 18 is specifically a plasmid, not a phage.
• Bacteria used for transformation: Bacteria are often used as host organisms for transformation, but pUC 18 is not a bacterium. It is a plasmid that can be introduced into bacterial cells for replication and gene expression.
• Restriction endonuclease: Restriction endonucleases are enzymes that cleave DNA at specific recognition sequences. pUC 18 is not an enzyme; it is a plasmid that can be cut by restriction enzymes at specific sites for genetic manipulation.

Answer: Transfection

Transfection refers to the deliberate introduction of foreign DNA into a host cell, specifically in animal cells. This process bypasses the natural barrier of the cell membrane to deliver the DNA, often using techniques like liposomes, electroporation, or viral vectors. It allows scientists to study gene function, introduce therapeutic genes, or create genetically modified animal models.

The other options are incorrect:

• Transversion: This term describes a specific type of point mutation where one purine base (e.g., adenine, guanine) is replaced with another purine or one pyrimidine base (e.g., cytosine, thymine) is replaced with another pyrimidine. It’s not related to introducing foreign DNA.
• Conversion: This term can refer to different biological processes, but in the context of DNA, it describes the exchange of two identical DNA strands between homologous chromosomes during crossing over in meiosis. It doesn’t involve introducing foreign DNA.
• Inversion: This describes a type of chromosomal mutation where a segment of DNA is flipped within the same chromosome. While it involves rearranging existing DNA, it doesn’t introduce foreign DNA from another source.

Answer: Diploid & alike to that of the donor’s somatic cells

The cloned sheep “Dolly” had a diploid genotype that was identical to that of the donor sheep’s somatic cells. In the process of somatic cell nuclear transfer (SCNT), the nucleus of a somatic cell (donor cell) is transferred into an enucleated egg cell, and the resulting clone has a genetic makeup identical to the donor organism.

The other options are incorrect:

• Haploid and identical to that of mother’s egg cell: Clones are formed from the fusion of a somatic cell nucleus (which is diploid) with an enucleated egg cell. The resulting organism is diploid, not haploid.
• Diploid & alike to that of mother’s somatic cells: While Dolly’s genetic material was derived from the somatic cells of the donor, it was not identical to the mother’s somatic cells. The genetic material came from the donor, not the egg cell provider.
• Diploid with the haploid set of chromosomes from the father and other from the mother: This describes the normal process of sexual reproduction, where offspring inherit half of their genetic material from each parent. However, Dolly was a clone produced through asexual reproduction using somatic cell nuclear transfer, so she had a diploid genotype identical to that of the donor.

Answer: Stem cells

Stem cells are undifferentiated cells with the ability to give rise to various cell types. Pluripotent stem cells, in particular, have the capacity to differentiate into cells of all three germ layers. Cells derived from the early pre-implantation stage of an embryo, such as embryonic stem cells (ESCs) in mice, are pluripotent and can differentiate into a wide range of cell types.

The other options are incorrect:

• Organ culture: Organ culture involves growing and maintaining organs or tissues outside of the organism. It is not specifically related to pluripotent cells derived from early pre-implantation embryos.
• Somatic cell hybridization: Somatic cell hybridization involves the fusion of cells from different tissues, typically with the goal of combining specific traits. It is not the term used for pluripotent cells derived from early embryos.
• Hybridoma: A hybridoma is a cell line formed by the fusion of a specific type of immune cell with a myeloma cell. This process is commonly used in the production of monoclonal antibodies but is not related to pluripotent cells from early embryos.

Answer: Palindromic DNA

A palindromic sequence is one that reads the same backward and forward. In DNA, this means the strand can be read in one direction and then reversed, resulting in the same sequence. This ability arises from the specific base pairing between adenine (A) and thymine (T) and guanine (G) and cytosine (C). For example, the sequence ACCTAGGT is palindromic because reading it from right to left (TGGATCCA) reveals the same sequence.

The other options are incorrect:

• Complementary DNA: Complementary DNA (cDNA) is a single-stranded DNA molecule synthesized from mRNA. While it forms pairs with the original mRNA in a specific way, it’s not necessarily palindromic, as the mRNA sequence itself wouldn’t be mirrored in the cDNA.
• Plasmid DNA: Plasmids are small, circular DNA molecules that can replicate independently within a host cell. While they may contain specific palindromic sequences for various purposes, the entire plasmid molecule wouldn’t necessarily be palindromic.
• Copy DNA: Copy DNA is a term often used in the context of DNA replication, referring to the newly synthesized DNA strand. It shares the same sequence as the template strand but isn’t inherently palindromic unless the template itself is palindromic.

Answer: Protein

Humulin is the brand name for recombinant human insulin. Insulin itself is a protein hormone composed of two polypeptide chains linked by disulfide bonds. It plays a crucial role in regulating blood sugar levels by promoting glucose uptake into cells. Recombinant DNA technology allows for the production of this protein by inserting the human insulin gene into a host organism (often bacteria) that then expresses the gene and synthesizes the insulin molecule.

The other options are incorrect:

• Lipid: Lipids are a diverse group of biomolecules including fats, oils, and waxes. They are typically composed of glycerol and fatty acids and lack the amino acid chains characteristic of proteins.
• Monosaccharide: Monosaccharides are simple sugars, the building blocks of carbohydrates. They contain only one sugar molecule, whereas proteins are complex molecules made up of many amino acids.
• Vitamin: Vitamins are essential organic compounds needed in small amounts for normal body functions. Humulin, as a protein hormone, has a different biological function and structure compared to vitamins.

Answer: RFLP

DNA fingerprinting is a technique used to identify and analyze the unique patterns in an individual’s DNA. RFLP involves the use of restriction enzymes to cut DNA at specific sites, producing fragments of varying lengths. The resulting pattern of fragments is unique to each individual, forming the basis for DNA fingerprinting.

The other options are incorrect:

• Hybridoma: Hybridoma technology is associated with the production of monoclonal antibodies by fusing antibody-producing B cells with myeloma cells. It is not directly related to DNA fingerprinting.
• Site-specific mutagenesis: Site-specific mutagenesis involves the targeted alteration of specific nucleotides in a DNA sequence. It is a method used for introducing specific mutations but is not directly associated with DNA fingerprinting.
• Shotgun cloning: Shotgun cloning is a method used in DNA sequencing where random fragments of a genome are cloned and then sequenced. While it is related to DNA sequencing, it is not specifically associated with DNA fingerprinting.

Answer: Cloning and in vitro culture

Cloning involves the production of genetically identical organisms or cells from a single parent organism. In the context of this question, in vitro culture refers to the growth of cells or tissues outside of the organism in a controlled environment. Together, cloning and in vitro culture are used to generate a large number of genetically identical offspring.

The other options are incorrect:

• Polymerase chain reaction (PCR): This technique amplifies specific DNA sequences but doesn’t create new organisms or offspring. While it can be used to generate large amounts of DNA, it doesn’t produce genetically identical individuals.
• Chromatography: This technique separates different molecules based on their properties, such as size and charge. It’s not directly related to reproduction or creating genetically identical offspring.
• Electrophoresis: This technique separates molecules based on their size and charge applied in an electric field. It’s often used in conjunction with other techniques, such as DNA analysis, but doesn’t produce new organisms or offspring.

Answer: They cut DNA at a few restricted sites

Restriction endonucleases are enzymes that cleave DNA molecules at specific recognition sites. These sites are often palindromic sequences, meaning the sequence reads the same backward and forward. The term “restriction” comes from the fact that these enzymes restrict or limit their activity to specific, well-defined DNA sequences.

The other options are incorrect:

• They have a very restrictive or site-specific endonuclease activity: This option is essentially restating the correct explanation. Restriction endonucleases are called “restriction” because of their site-specific cleavage activity.
• They restrict the entry of foreign DNA into the cell by cleaving the DNA due to endonuclease activity: While restriction endonucleases play a role in protecting bacteria from foreign DNA, the term “restriction” does not specifically refer to restricting the entry of foreign DNA. It is more about the enzymes’ specificity for particular DNA sequences.
• Their distribution is restricted to only some bacterial cells: The distribution of restriction endonucleases is indeed more common in bacterial cells, but the term “restriction” does not refer to their distribution. It is related to the specific cleavage sites on DNA.

Answer: Produces only specific antibodies only against a specific antigen

A hybridoma cell is created by fusing a B lymphocyte (immune cell) with a myeloma cell (cancerous plasma cell). This hybrid cell inherits the antibody production capability of the B cell and the immortality of the myeloma cell. However, the key characteristic of a hybridoma cell is its specificity. It produces only one type of antibody, specifically targeted towards a single antigen. This is because the hybridoma inherits the genetic information for that specific antibody from the B cell it originated from.

The other options are incorrect:

• Produces different types of antibodies against different types of antigens: This is not a characteristic of a hybridoma cell. Each hybridoma cell is programmed to produce only one specific antibody against a single antigen.
• Produces different types of antibodies but only one type of antigen: This is a contradiction within itself. A hybridoma cell produces only one type of antibody, so it cannot produce different types of antibodies against the same antigen.

Answer: Continuous growth of hybridoma

In hybridoma technology, a hybridoma is created by fusing a specific type of immune cell (B cell) with a myeloma cell, which is a cancerous plasma cell. The myeloma cell contributes the ability for continuous and rapid cell division, ensuring the perpetual growth of the hybridoma cell line.

The other options are incorrect:

• Production of antibodies: While the hybridoma as a whole produces antibodies, it’s the normal B cell component that contributes the specificity for antibody production against a particular antigen. The myeloma cell’s role is primarily to support the continuous growth of the hybridoma.
• Both “Continuous growth of hybridoma” and “Production of antibodies”: This option is partially correct, but it is not specific enough. The myeloma cell’s main contribution is the continuous growth of the hybridoma, while the antibody production is mainly attributed to the normal B cell component of the hybridoma.
• Neither “Continuous growth of hybridoma” nor “Production of antibodies”: This option is incorrect because the myeloma cell is crucial for the continuous growth of the hybridoma, even though the hybridoma as a whole is responsible for antibody production.

Answer: E. coli

Escherichia coli (E. coli) is a bacterium commonly used in biotechnology for the production of various recombinant proteins, including insulin. The human insulin gene is introduced into E. coli, and these bacteria are then cultured in large fermentation tanks to produce insulin in significant quantities.

The other options are incorrect:

• Plasmodium: Plasmodium is a protozoan parasite responsible for causing malaria. It is not used for the production of recombinant insulin.
• Agrobacterium: Agrobacterium tumefaciens is a bacterium used for transferring genes into plants. It is not commonly used for producing recombinant insulin.
• Rhizobium: Rhizobium is a bacterium that forms symbiotic relationships with legume plants, aiding in nitrogen fixation. It is not used for the large-scale production of recombinant insulin.

Answer: It is specific to a single antigenic determinant of a single antigen

Monoclonal antibodies are produced from a single clone of identical immune cells. As a result, each monoclonal antibody is specific to a single epitope (antigenic determinant) of a single antigen. This specificity is a unique feature of monoclonal antibodies.

The other options are incorrect:

• It is non-specific: This is completely opposite to the characteristic of a monoclonal antibody. Their high specificity is what makes them unique and valuable.
• It is specific to a few antigenic determinants: While some monoclonal antibodies may bind to a few related epitopes on an antigen, their specificity is still much higher compared to the broad range of targets conventional antibodies recognize.
• Restricted growth: This might refer to the limited lifespan of a particular hybridoma cell line producing the monoclonal antibody, but it’s not the defining characteristic of the antibody itself.

Answer: Polymerase chain reaction

A thermal cycler is a laboratory device used to amplify DNA through the polymerase chain reaction (PCR). PCR is a technique that enables the rapid production of a large number of copies of a specific DNA sequence. The thermal cycler is essential in PCR as it allows for precise temperature control, facilitating the denaturation, annealing, and extension steps required for DNA amplification.

The other options are incorrect:

• Enzyme-linked immune-sorbent assay (ELISA): While ELISA also involves temperature control, the specific heating cycles used in PCR are not required. Instead, ELISA relies on enzymatic and immunological reactions for antigen detection.
• Ligation reaction: Although temperature control can be relevant in some ligation reactions, the precise cycling profile of a thermal cycler is not typically needed. Ligation enzymes work best at constant temperatures specific to their activity.
• Immobilization reaction: This term refers to binding molecules to a solid surface and doesn’t involve the specific temperature cycling characteristic of a thermal cycler.

Answer: Cleaving DNA with restriction endonuclease and joining with ligase

The process of constructing a recombinant DNA involves using a restriction endonuclease to cut the DNA at specific recognition sites (generating cohesive or sticky ends), and then using DNA ligase to join the cut DNA fragments together. This results in a new combination of genetic material, creating a recombinant DNA molecule.

The other options are incorrect:

• Cleaving DNA with ligase and joining with endonuclease: This reverses the order of the key steps. Ligase needs pre-existing complementary ends to join, which are created by the cleaving action of restriction enzymes.
• Cleaving and joining DNA with restriction endonuclease: While restriction enzymes can cleave DNA, they cannot directly join the fragments. DNA ligase is needed for this final step.
• Cleaving DNA with restriction endonuclease and joining with polymerase: Polymerase enzymes are involved in copying DNA, not directly joining pre-existing fragments. The sticky ends created by restriction enzymes are specifically designed to be ligated, not polymerase-dependent.

Answer: Restriction endonuclease

ECOR1 (or EcoRI) is a type II restriction endonuclease. It recognizes a specific DNA sequence and cleaves the DNA at that site. Restriction endonucleases like ECOR1 are commonly used in molecular biology for DNA manipulation, including the construction of recombinant DNA molecules.

The other options are incorrect:

• DNA ligase enzyme: DNA ligase is an enzyme that joins or seals nicks in the phosphodiester backbone of DNA strands. ECOR1, however, is a restriction endonuclease, which cleaves DNA at specific sites.
• A vector used for insulin synthesis: ECOR1 is not a vector itself; it is an enzyme. Vectors are usually plasmids or other DNA molecules used to carry and replicate foreign genes. ECOR1 is used for cutting and manipulating DNA.
• A plasmid used as a vector: ECOR1 is not a plasmid. It is a restriction endonuclease enzyme. Plasmids are often used as vectors in genetic engineering, but ECOR1 is involved in the DNA cleavage

Answer: Genetic finger printing

Genetic fingerprinting, also known as DNA fingerprinting or DNA profiling, is a technique used to compare and analyze DNA samples. It is commonly employed in forensic science, paternity testing, and criminal investigations to establish the identity or relatedness of individuals based on their unique DNA profiles.

The other options are incorrect:

• Hybridoma technology: Hybridoma technology is used for producing monoclonal antibodies and is not directly related to comparing DNA samples.
• ELISA: Enzyme-Linked Immunosorbent Assay (ELISA) is an immunological assay used for detecting the presence of specific proteins, not for comparing DNA samples.
• Gene therapy: Gene therapy involves the introduction or modification of genes in living organisms to treat or prevent diseases. It is not a technique specifically used for comparing DNA samples.

Answer: They can develop into any tissue of the body

Pluripotent stem cells have the capacity to differentiate into cells of all three germ layers: ectoderm, endoderm, and mesoderm. This gives them the ability to develop into any tissue type in the body, making them highly versatile in their potential for differentiation.

The other options are incorrect:

• They can develop into whole individuals: This statement is incorrect. Pluripotent stem cells have the potential to differentiate into a variety of cell types, but they cannot develop into whole individuals. The ability to give rise to an entire organism is characteristic of totipotent cells.
• They help in the production of monoclonal antibodies: Pluripotent stem cells are not directly involved in the production of monoclonal antibodies. Hybridoma technology, which involves the fusion of specific immune cells, is used for generating monoclonal antibodies.

Answer: Embryo, bone marrow, umbilical cord blood etc

Stem cells can be sourced from various tissues and stages of development. Common sources include embryos (embryonic stem cells), bone marrow (hematopoietic and mesenchymal stem cells), and umbilical cord blood (rich in hematopoietic stem cells). These sources offer different types of stem cells with varying degrees of differentiation potential.

The other options are incorrect:

• Embryo only: This statement is incorrect. While embryos are a source of embryonic stem cells, stem cells can also be obtained from various other tissues such as bone marrow, umbilical cord blood, and adult tissues.
• Any part of the body: This statement is overly broad and not entirely accurate. While some tissues in the body contain stem cells, not every part of the body is a viable source. Common sources include bone marrow, blood, and certain tissues.
• Blood only: Blood does contain stem cells, particularly hematopoietic stem cells, but it is not the only source. Stem cells can also be found in other tissues and organs throughout the body.

Answer: Monoclonal

Hybridoma technology involves the fusion of specific immune cells, typically B cells, with myeloma cells to produce hybrid cells called hybridomas. These hybridomas are capable of continuously producing identical antibodies. Therefore, antibodies generated through hybridoma technology are monoclonal antibodies.

The other options are incorrect:

• Polyclonal: This option is incorrect. Polyclonal antibodies are produced by a diverse population of B cells and recognize multiple epitopes on an antigen. Hybridomas, in contrast, produce monoclonal antibodies specific to a single epitope.
• Non-active: The term “non-active” is not applicable to antibody production through hybridoma technology. Monoclonal antibodies can be highly specific and active in binding to their target antigens.
• Over-active: The term “over-active” is not an accurate description of antibodies produced through hybridoma technology. The activity of monoclonal antibodies is precisely controlled and directed toward a specific antigen due to their monoclonal nature.

Answer: UUU

The codons UAG, UAA, and UGA are termination codons (also known as stop codons) that signal the end of protein synthesis. UUU, on the other hand, codes for the amino acid phenylalanine and is not a termination codon.

The other options are incorrect:

• UAG: This is a stop codon known as amber.
• UAA: This is another stop codon known as ochre.
• UGA: This is the third stop codon known as opal.

Answer: Plasma cell

Plasma cells, also known as effector B cells or antibody-secreting cells, are a differentiated form of B lymphocytes. Their primary function is to produce and secrete antibodies (immunoglobulins) in response to specific antigens. These antibodies play a crucial role in the immune system’s defense against pathogens.

The other options are incorrect:

• Memory cell: Memory cells are a type of B lymphocyte that “remembers” specific antigens from previous encounters. They do not actively produce antibodies but can mount a rapid and specific response upon re-exposure to the antigen.
• Adipocyte: Adipocytes are fat cells and are not involved in antibody production. They are specialized for storing and releasing energy in the form of lipids.
• Erythrocyte: Erythrocytes, or red blood cells, are responsible for oxygen transport and do not produce antibodies. They lack a nucleus and many other cellular organelles, including those needed for antibody synthesis.

Answer: Hybridoma cells

Hybridoma cells are created by the fusion of specific antibody-producing B cells with myeloma cells, which are cancerous plasma cells. Hybridomas are capable of continuously producing monoclonal antibodies—identical antibodies that are specific to a single epitope or antigen.

The other options are incorrect:

• Myeloma cells: While myeloma cells contribute to the immortality of hybridoma cells, they cannot produce antibodies on their own. They lack the essential genetic information from the B lymphocyte.
• Monocytes: These are white blood cells with different functions within the immune system. They are not involved in antibody production.
• Adipocytes: These are fat cells, completely unrelated to the immune system or antibody production.

Answer: Both “In vivo in the peritoneal cavity of mice” and “In vitro in large scale culture vessels”

Monoclonal antibodies can be produced using two main techniques:

In vivo in the peritoneal cavity of mice: The original method involves injecting hybridoma cells into the peritoneal cavity of mice, where they grow and produce antibodies. The antibodies are then harvested from the mice.
In vitro in large scale culture vessels: This modern approach involves growing hybridoma cells in large-scale culture vessels, such as bioreactors or fermenters. This allows for the controlled and efficient production of monoclonal antibodies in a more scalable and controllable manner.

The other options are incorrect:

• In vivo in the peritoneal cavity of mice: This statement is correct. However, the option is incorrect because both techniques (in vivo and in vitro) can be used for large-scale production.
• In vitro in large scale culture vessels: This statement is correct. However, the option is incorrect because both techniques (in vivo and in vitro) can be used for large-scale production.
• Neither “In vivo in the peritoneal cavity of mice” nor “In vitro in large scale culture vessels”: This option is incorrect because both techniques are used for large-scale production of monoclonal antibodies.

Answer: Stem cell therapy

Stem cell therapy involves the use of stem cells to repair or replace damaged tissues and organs. In the context of spinal cord injuries, stem cell therapy aims to regenerate and repair the damaged spinal cord tissue. Stem cells can differentiate into various cell types, potentially promoting tissue repair and improving function.

The other options are incorrect:

• Hybridoma: Hybridoma technology is not a therapy for spinal cord injuries. It is a method used for producing monoclonal antibodies.
• Gene therapy: Gene therapy involves the introduction, removal, or change of genetic material to treat or prevent disease. While it holds promise for various conditions, it is not the primary therapy for spinal cord injuries.
• Recombinant DNA technology: Recombinant DNA technology is a broad term encompassing various techniques used in genetic engineering. It is not a specific therapy for spinal cord injuries but may contribute to understanding and developing treatments for various conditions.

Answer: Complementary DNA

cDNA is generated from messenger RNA (mRNA) through a process called reverse transcription. The enzyme reverse transcriptase synthesizes a complementary DNA strand based on the sequence of the mRNA. This cDNA is complementary to the original mRNA sequence and serves as a stable copy of the protein-coding information.

The other options are incorrect:

• Competitive DNA: This term is not associated with cDNA. Competitive DNA typically refers to DNA sequences used as competitors in various molecular biology assays.
• Chemical DNA: While cDNA is a type of DNA, the term “Chemical DNA” is not specific and does not convey the process or origin of cDNA.
• Complex DNA: “Complex DNA” is not a term used in the context of recombinant DNA technology. cDNA specifically refers to the complementary DNA synthesized from mRNA.

Answer: Taq DNA polymerase

Taq DNA polymerase is a heat-stable enzyme derived from the thermophilic bacterium Thermus aquaticus. It is a key component in the polymerase chain reaction (PCR), where it facilitates the synthesis of DNA strands by extending primers and incorporating nucleotides at high temperatures.

The other options are incorrect:

• HRP: HRP (Horseradish Peroxidase) is not used in PCR. It is an enzyme commonly used in various immunoassays for detecting the presence of specific proteins.
• EcoRI: EcoRI is a restriction endonuclease, not a DNA polymerase. It is used for cutting DNA at specific recognition sites and is not involved in the synthesis of DNA strands during PCR.
• EcoRII: EcoRII is another type of restriction endonuclease and is not used in PCR. Similar to EcoRI, its primary function is the cleavage of DNA at specific sites.

Answer: HRP

Horseradish Peroxidase (HRP) is an enzyme commonly used as a detection enzyme in Enzyme-Linked Immunosorbent Assay (ELISA). In ELISA, HRP catalyzes a colorimetric or chemiluminescent reaction that produces a detectable signal, indicating the presence of specific antibodies or antigens.

The other options are incorrect:

• Taq DNA polymerase: Taq DNA polymerase is not used in ELISA. It is a DNA polymerase enzyme primarily employed in polymerase chain reaction (PCR) for DNA amplification.
• EcoRI: EcoRI is a restriction endonuclease and is not used in ELISA. Its main function is to cleave DNA at specific recognition sites.
• EcoRII: Similar to EcoRI, EcoRII is a restriction endonuclease and is not used in ELISA. Its primary role is the cleavage of DNA at specific sites.

Answer: RFLP

RFLP involves the use of restriction enzymes to cleave DNA at specific recognition sites, generating fragments of varying lengths. Polymorphisms in these fragment lengths can be unique to individuals or populations, providing a basis for DNA fingerprinting and distinguishing one individual’s DNA from another.

The other options are incorrect:

• PCR (Polymerase Chain Reaction): PCR is a technique for amplifying specific DNA sequences but does not inherently provide information about DNA differences between individuals.
• Reverse transcriptase: Reverse transcriptase is an enzyme used in reverse transcription, converting RNA into cDNA. It is not directly related to distinguishing DNA between individuals.
• cDNA (Complementary DNA): cDNA is synthesized from mRNA and is not typically used in distinguishing DNA differences between individuals. It is commonly employed in gene expression studies.

Answer: Genome, chromosome, gene, nucleotide

The organization of genetic material follows a hierarchical structure, with larger units containing smaller ones:

• Genome: This refers to the entire set of genetic material of an organism, including all its chromosomes and non-coding DNA sequences.
• Chromosome: Chromosomes are linear structures made up of DNA, genes, and proteins. They are the most condensed form of genetic material within a cell.
• Gene: Genes are specific regions of DNA that contain the instructions for building proteins or other functional molecules.
• Nucleotide: Nucleotides are the building blocks of DNA and RNA. They consist of a sugar molecule, a phosphate group, and a nitrogenous base.

The other options are incorrect:

• Nucleotide, gene, chromosome, genome: This reverses the order of organization, starting with the smallest unit and progressing to the largest.
• Gene, nucleotide, chromosome, genome: This incorrectly places genes before chromosomes and nucleotides before genes.
• Chromosome, genome, nucleotide, gene: This also reverses the order, placing chromosomes before the genome and nucleotides before genes.

Answer: A hybrid cell obtained by fusing a β–lymphocyte with a myeloma cell in vitro

A hybridoma is a specifically engineered cell created by fusing a B-lymphocyte (an antibody-producing white blood cell) with a myeloma cell (a cancerous plasma cell). This fusion takes place in vitro, meaning within a laboratory culture dish or other controlled environment.

The other options are incorrect:

• A hybrid cell obtained by fusing a β-lymphocyte with a myeloma cell in vivo: While theoretically possible, in vivo fusion is not the common method for creating hybridomas. In vitro fusion offers greater control and predictability.
• A hybrid cell obtained by fusing 2 β-lymphocyte cells in vitro: Fusing two B-lymphocytes wouldn’t create a hybridoma with the desired properties. Myeloma cells contribute the crucial element of immortality to the hybrid cell.
• A hybrid cell obtained by fusing any 2 body cells in vitro: Hybridoma creation involves a specific combination of cell types with distinct functions. Fusing any two random body cells wouldn’t result in a hybridoma with its unique characteristics.

Answer: All of these

Monoclonal antibodies have diverse applications in the field of medicine and diagnostics. They are utilized in.

• Disease diagnosis: Monoclonal antibodies can be designed to recognize specific disease markers, aiding in the diagnosis of various medical conditions.
• Detection of specific types of pathogens: Monoclonal antibodies can be engineered to target and detect specific pathogens, such as bacteria or viruses, facilitating accurate and specific diagnostics.
• Very early and accurate detection of cancer: Monoclonal antibodies can be employed in cancer diagnostics to detect specific cancer markers, allowing for early and precise identification of cancerous cells.

Answer: Serine

Serine is one of the 11 non-essential amino acids, meaning our body can synthesize it from other molecules like glucose and glutamine.

The other options are incorrect:

• Threonine: This is an essential amino acid, so our body cannot produce it and we must obtain it from our diet.
• Lysine: Another essential amino acid that needs to be consumed through food.
• Histidine: While essential for infants and growing children, histidine becomes non-essential in adults as our bodies can usually produce it in sufficient amounts.

Answer: Phenylalanine

Essential amino acids are those that the human body cannot synthesize on its own and must be obtained from the diet. Phenylalanine is one such essential amino acid, and it serves as a precursor for the synthesis of other important molecules, including tyrosine.

The other options are incorrect:

• Cysteine: Cysteine is a non-essential amino acid, as the body can synthesize it from methionine. However, cysteine becomes conditionally essential in certain situations, such as during periods of illness or stress.
• Asparagine: Asparagine is a non-essential amino acid, as the body can produce it. It is not categorized as essential for human nutrition.
• Glutamine: Glutamine is a non-essential amino acid, meaning the body can synthesize it. While it plays various roles in the body, it is not considered essential for dietary intake.

Answer: Covalent bond

A peptide bond is a type of strong covalent bond formed between the α-amino group of one amino acid and the α-carboxyl group of another. This connection links amino acids to create peptides and proteins. Covalent bonds involve sharing electrons between two atoms, which provides stability and strength to the peptide chain.

The other options are incorrect:

• Ionic bond: These involve an attraction between ions with opposite charges (positive and negative). Peptide bonds don’t involve charged atoms so ionic bonds wouldn’t apply.
• Metallic bond: These involve shared electrons among many atoms within a metal lattice. Peptide bonds form between specific atoms within amino acids, not across a large structure like metal atoms.
• Hydrogen bond: While hydrogen bonds can exist between side chains of amino acids or between protein molecules, they don’t directly link the backbone amino acids together. The peptide bond itself is a covalent bond.

Answer: 3 amino acids and 2 peptide bonds

Short Explanation: A tripeptide is a type of peptide formed by linking three amino acids with two peptide bonds. Each peptide bond joins the α-amino group of one amino acid to the α-carboxyl group of the next, leading to a chain of three amino acids connected by two bonds.

The other options are incorrect:

• 3 amino acids and 1 peptide bond: This would only connect two amino acids, not three, resulting in a dipeptide instead of a tripeptide.
• 3 amino acids and 3 peptide bonds: This would create a tetrapeptide, a molecule with four amino acids linked by three peptide bonds.
• 3 amino acids and 4 peptide bonds: This is not possible because each amino acid only has one α-amino group and one α-carboxyl group available for forming peptide bonds. Therefore, three amino acids can only form a maximum of three peptide bonds, not four.

Answer: Two light chains and two heavy chains joined by disulfide bond

mmunoglobulins, also known as antibodies, are Y-shaped proteins crucial for the immune system. They consist of two identical heavy chains and two identical light chains, all connected by disulfide bonds. These bonds are strong covalent linkages formed between cysteine residues in the different chains, providing stability and structural integrity to the immunoglobulin molecule.

The other options are incorrect:

• A light chain and two heavy chains joined by disulfide bond: This configuration is incorrect. Immunoglobulins always have two light chains.
• Two light chains and a heavy chain joined by disulfide bond: Again, immunoglobulins require two heavy chains, not one.
• Two light chains and two heavy chains joined by hydrogen bond: While hydrogen bonds might be present within different domains of an immunoglobulin, the primary linkage between chains happens through disulfide bonds, not hydrogen bonds.

Answer: Chromatogram

The pattern formed by separated components on the stationary phase in chromatography is called a chromatogram. It visually represents the separation of a mixture based on the different interactions between components and the mobile phase.

The other options are incorrect:

• Chroming: This term doesn’t specifically refer to the pattern in chromatography. It might be used informally to describe the process of performing chromatography.
• Chroma: While related to color and used in chromatography descriptions, chroma specifically refers to the intensity or saturation of a color, not the pattern itself.
• Chromatograph: This refers to the entire apparatus used for performing chromatography, not just the resulting pattern on the stationary phase.

Answer: IgA

IgA is the predominant antibody found in mucous membranes and exocrine secretions like tears, saliva, colostrum, and respiratory and intestinal fluids. These secretions form the first line of defense against pathogens entering the body through these surfaces. IgA offers local protection through various mechanisms, including neutralizing viruses and bacteria, preventing their attachment to epithelial cells, and promoting their expulsion.

The other options are incorrect:

• IgE: Primarily involved in allergic reactions and defense against parasites, IgE is not abundant in secretory fluids.
• IgG: While the most common antibody in blood and extracellular fluids, IgG levels are very low in secretions like tears and saliva.
• IgM: Mainly involved in early immune responses and agglutination of pathogens, IgM is not highly prevalent in secretions.

Answer: Denaturation

Denaturation refers to the unfolding and loss of the native three-dimensional structure of a protein molecule. This disrupts the intricate arrangement of hydrogen bonds, ionic bonds, and other interactions that maintain the protein’s proper shape and function. Denaturation usually leads to loss of the protein’s function.

The other options are incorrect:

• Renaturation: This is the opposite of denaturation and refers to the process where a denatured protein refolds back into its native structure and regains its function.
• Oxidation: While oxidation can involve changes in protein structure, it specifically refers to the loss of electrons from the molecule, often affecting specific amino acid side chains. It doesn’t necessarily lead to complete unfolding like denaturation.
• Reduction: Similar to oxidation, reduction involves gaining electrons and primarily affects specific amino acid side chains, not necessarily causing the entire protein to unfold like denaturation.

Answer: Folding

Protein folding is the process by which a linear chain of amino acids, called a polypeptide, acquires its three-dimensional structure, also known as conformation. This intricate structure is crucial for the protein’s function, as it determines its interactions with other molecules and its ability to carry out specific tasks within the cell. Folding involves the formation of various chemical bonds and interactions between different amino acid residues in the chain, such as hydrogen bonds, ionic bonds, and disulfide bonds.

The other options are incorrect:

• Denaturing: This refers to the process where a protein loses its native structure and function. It is the opposite of folding and leads to a non-functional protein.
• Synthesis: This refers to the process of building a protein molecule from individual amino acids, but it doesn’t involve acquiring the specific three-dimensional shape necessary for function.
• Hydrolysis: This is the breakdown of a protein molecule into smaller components like amino acids. It is the opposite of protein synthesis and destroys the protein’s structure, not forming it.

Answer: Proline

Proline is unique among amino acids because its side chain forms a ring structure, which includes the nitrogen atom of the amino group. This distinctive structure classifies proline as an imino acid, a subtype of amino acids. The presence of the imino group in its side chain influences the conformation and structure of proteins, as it introduces a kink in the polypeptide chain.

The other options are incorrect:

• Alanine: Alanine is a standard amino acid with a simple aliphatic side chain. It is not classified as an imino acid.
• Glycine: Glycine is the simplest amino acid and has a hydrogen atom as its side chain. It is not an imino acid.
• Serine: Serine is a standard amino acid with a hydroxyl group in its side chain. It is not classified as an imino acid.

Answer: IgG and IgM both are involved in primary immune response

While both IgG and IgM play crucial roles in the immune response, their involvement differs slightly:

• IgM: This is the predominant antibody produced during the primary immune response. It binds to pathogens with low specificity but high avidity (binding strength), triggering their agglutination and activation of the complement system.
• IgG: While not the first antibody produced, IgG rises rapidly during the primary response and becomes the dominant antibody in later stages. It exhibits higher specificity than IgM and is more efficient at neutralizing pathogens and promoting their clearance.

The other options are incorrect:

• IgG is involved in primary immune response: While IgG is involved in the primary response, it’s not the sole player.
• IgM is involved only in primary immune response: While IgM is predominant in the primary response, it also participates in secondary responses to some degree.
• IgG is involved only in secondary immune response: While IgG plays a more prominent role in secondary responses, it’s still present during the primary phase.

Answer: Dinitrogenase reductase

In biological nitrogen fixation, the key enzyme responsible for nitrogen gas (N₂) reduction to ammonia (NH₃) is dinitrogenase reductase. It forms the second part of the dinitrogenase enzyme complex, alongside dinitrogenase (component I). Dinitrogenase reductase (component II) transfers electrons to dinitrogenase, enabling it to break the triple bond of N₂ and convert it to NH₃.

The other options are incorrect:

• Dinitrogenase oxidase: This term doesn’t exist in the context of biological nitrogen fixation. There’s no enzyme oxidase involved in this process.
• Phosphatase: This enzyme removes phosphate groups from molecules and plays no role in nitrogen fixation.
• Kinase: Kinases add phosphate groups to molecules, again irrelevant to nitrogen fixation.

Answer: Ingest large particles and cells by phagocytes

Macrophages are incredibly versatile immune cells known for their phagocytic abilities. They act as the body’s janitors, engulfing and digesting large particles, debris, and even whole cells like bacteria and dead cells through a process called phagocytosis. This helps maintain tissue integrity, remove pathogens, and initiate immune responses.

The other options are incorrect:

• Produce and secrete antibodies: While macrophages have some role in antibody production, it’s primarily the responsibility of plasma B cells.
• Interact with infected host cells through receptors on T-cell surface: This function is more characteristic of T cells, which directly recognize and attack infected host cells. Macrophages, however, can present antigens to T cells to activate them.
• Interact with macrophages and secrete cytokines: Macrophages do interact with each other and secrete cytokines, but the statement isn’t specific enough to be considered a main function. Phagocytosis, on the other hand, is a defining characteristic of these cells.

Answer: Produce and secrete antibodies

The primary function of B lymphocytes, also known as B cells, is to produce and secrete specialized proteins called antibodies. These antibodies bind to specific pathogens or foreign particles, marking them for elimination by other immune cells or neutralizing their activity. The ability to generate a diverse repertoire of highly specific antibodies allows the immune system to effectively combat different types of invaders.

The other options are incorrect:

• Ingest large particles and cells by phagocytosis: This function belongs to macrophages, another critical immune cell type. B cells lack the phagocytic machinery for engulfing large particles.
• Interact with infected host cells through receptors on T-cell surface: While B cells can interact with infected cells by presenting antigens to T cells, they don’t directly recognize and attack them like T cells do. T cells have specific receptors for antigen-major histocompatibility complex (MHC) complexes presented by other cells, including B cells.
• Interact with macrophages and secrete cytokines: B cells do collaborate with macrophages and other immune cells, but antibody production remains their core function. Cytokine secretion can be a secondary function involved in immune signaling, but not the primary one.

Answer: Interact with infected host cells through receptors on TCR

T lymphocytes, also known as T cells, play a crucial role in the body’s cell-mediated immune response. Their primary function is to directly recognize and attack infected host cells or activate other immune cells through specific receptors on their surface called T-cell receptors (TCR).

The other options are incorrect:

• Ingest large particles and cells by phagocytes: This function belongs to macrophages, not T cells. T cells lack the phagocytic machinery for engulfing large particles.
• Produce and secrete antibodies: This is the primary function of B lymphocytes, not T cells. While T cells can contribute to antibody production indirectly, it’s not their main role.
• Interact with macrophages and secrete cytokines: T cells do collaborate with macrophages and other immune cells through cytokine signaling, but their direct interaction with infected cells through TCR is their defining function.

Answer: Plasmid

A plasmid is an extra-chromosomal, self-replicating, closed, double-stranded, and circular DNA molecule. Plasmids are commonly found in bacteria and can carry genes that provide advantages such as antibiotic resistance or the ability to metabolize specific nutrients. They are distinct from the genomic DNA, which is part of the bacterial chromosome.

The other options are incorrect:

• Chromosome: Chromosomes are the main genetic material of a cell, residing within the nucleus and containing essential genes for cell function and development. They differ from plasmids in size, location, and replication methods.
• Genomic DNA: This term generally refers to the entire set of genetic material, including both chromosomal and extrachromosomal DNA like plasmids. While plasmids contain DNA, they’re distinct from genomic DNA due to their location and independent replication.
• Bacteriophage: These are viruses that specifically infect bacteria. While they contain DNA and can replicate within the host cell, they are not self-contained like plasmids and lack the same circular, closed-loop structure.

Answer: IgM

Among the listed immunoglobulins, IgM is the largest with a molecular weight of approximately 900 kDa. It consists of five identical Y-shaped units linked together by disulfide bonds, forming a pentameric structure. This larger size contributes to its unique functions in the immune system.

The other options are incorrect:

• IgA: While present in various forms, the most common secretory IgA is a monomer (single Y-shaped unit) with a molecular weight of around 150 kDa, significantly smaller than IgM.
• IgE: This immunoglobulin is a monomer with a molecular weight of about 190 kDa, smaller than IgM.
• IgG: The most abundant antibody in the blood, IgG exists in four subclasses ranging in size from 150 to 160 kDa, making them smaller than IgM.