Microbiology MCQs with Answer and Explnation | Chapter 11

Answer: Change from aerobic to anaerobic

The Pasteur effect is due to the change from aerobic to anaerobic respiration. When oxygen is available, cells prefer to use aerobic respiration to generate ATP, which is more efficient than anaerobic respiration. Aerobic respiration produces about 36 ATP molecules per glucose molecule, while anaerobic respiration only produces about 2 ATP molecules per glucose molecule.

The other options are incorrect:

• Providing oxygen to anaerobically respiring structures does not directly cause the Pasteur effect.
• Rapid utilization of ATP does not directly cause the Pasteur effect.
• Nonsynthesis of ATP is a consequence of the Pasteur effect, not a cause of it.

Answer: Trans location

Translocation involves the exchange of genetic material between non-homologous chromosomes. This can result in the movement of genes from one linkage group to another.

The other options are incorrect:

• Inversion involves the reversal of a segment of DNA. This does not change the location of genes on the chromosome.
• Crossing over involves the exchange of genetic material between homologous chromosomes. This can result in the recombination of genes, but it does not move genes from one linkage group to another.
• Duplication involves the replication of a segment of DNA. This can result in the presence of multiple copies of a gene, but it does not move genes from one linkage group to another.

Answer: Muton

A muton is a segment of DNA that is capable of undergoing a single point mutation. Point mutations are changes in a single nucleotide in a DNA sequence. They can be caused by a variety of factors, such as exposure to radiation or chemicals, or errors in DNA replication.

The other options are incorrect:

• A gene is a functional unit of DNA that codes for a protein or RNA molecule.
• A cistron is a functional unit of DNA that is responsible for a single polypeptide chain.
• A replicon is a unit of DNA that is capable of self-replication.

Answer: Replicated chromosomes to be separated at anaphase

During metaphase, the two chromatids of a replicated chromosome are aligned at the equator of the spindle fiber apparatus. At anaphase, the two chromatids of each chromosome are pulled apart and move to opposite poles of the cell.

The other options are incorrect:

• Homologous chromosomes are chromosomes that have similar genes and structures. They are not the same as chromatids.
• Non-homologous chromosomes are chromosomes that do not have similar genes and structures. They are not joined at the centromere.
• Maternal and paternal chromosomes are chromosomes that are inherited from parents. They are not joined at the centromere.

Answer: Oxido reductase

Malate dehydrogenase (MDH) is an enzyme that belongs to the oxidoreductase class of enzymes. It catalyzes the reversible oxidation of malate to oxaloacetate, using NAD+ as an electron acceptor. This reaction is part of the citric acid cycle, which is a key metabolic pathway in all living organisms.

The other options are incorrect:

• Transferases are enzymes that catalyze the transfer of functional groups from one molecule to another.
• Hydrolases are enzymes that catalyze the hydrolysis of chemical bonds.
• Isomerases are enzymes that catalyze the interconversion of isomers, which are molecules that have the same atoms but different arrangements of those atoms.

Answer: Bio and niacin genes

The attB site in E.coli is located between the bio and niacin genes. This site is where the bacteriophage λ integrates its DNA into the bacterial chromosome. The integration of λ DNA into the bacterial chromosome is a process called lysogeny, and it allows λ to replicate and be passed on to daughter cells without killing the bacteria.

The other answer choices are incorrect:

• Gal and biogenes: The gal gene is located near the attB site, but it is not directly adjacent to it.
• Gal and B genes: The B genes are located on a different part of the E.coli chromosome than the attB site.
• None of these: The attB site is located between the bio and niacin genes.

Answer: Structural gene

A gene that takes part in the synthesis of polypeptide is a structural gene. Structural genes contain the genetic information that is used to produce a specific polypeptide chain. Polypeptide chains are the building blocks of proteins.

The other answer choices are incorrect:

• Regulator gene: A regulator gene is a gene that controls the expression of other genes. Regulator genes do not directly code for polypeptide chains.
• Operator gene: An operator gene is a DNA sequence that is located near a promoter and that can bind to a repressor protein. Operator genes control the expression of structural genes.
• Promoter gene: A promoter gene is a DNA sequence that is located upstream of a structural gene and that is necessary for transcription of the gene. Promoter genes do not directly code for polypeptide chains.

Answer: S – phase

DNA replicates during the S (Synthesis) phase of the cell cycle. The S phase is the period of DNA synthesis, when the cell’s DNA is replicated in preparation for cell division. During the S phase, the DNA double helix unwinds and each strand is copied to produce two identical daughter strands. The daughter strands then remain attached to each other at the centromere until they are separated during cell division.

The other phases of the cell cycle are:

• G1 phase: The G1 phase is the period of cell growth and preparation for DNA synthesis. During the G1 phase, the cell grows in size and produces the necessary proteins and enzymes for DNA replication.
• G2 phase: The G2 phase is the period of cell growth and preparation for cell division. During the G2 phase, the cell checks that its DNA has been replicated correctly and prepares for the mitosis phase.
• M phase: The M phase is the period of cell division. During the M phase, the cell’s chromosomes are separated and the cell divides into two daughter cells.

Answer: Prophase I

Prophase I is the first stage of meiosis, and it is during this stage that the homologous chromosomes pair up and exchange segments of DNA. Crossing-over is a type of genetic recombination, and it can lead to the creation of new combinations of genes.

The other stages of meiosis are:

• Metaphase I: During metaphase I, the paired homologous chromosomes line up at the equator of the spindle.
• Anaphase I: During anaphase I, the homologous chromosomes are pulled apart to opposite poles of the cell.
• Telophase I: During telophase I, the nuclear envelope reforms around the chromosomes at each pole of the cell.
• Prophase II: During prophase II, the nuclear envelope breaks down again, and the chromosomes become visible.
• Metaphase II: During metaphase II, the chromosomes line up at the equator of the spindle.
• Anaphase II: During anaphase II, the sister chromatids of each chromosome are pulled apart to opposite poles of the cell.
• Telophase II: During telophase II, the nuclear envelope reforms around the chromosomes at each pole of the cell.

Answer: Semiconservative

DNA replication is semiconservative, which means that each strand of the DNA double helix acts as a template for the synthesis of a new, complementary strand. The new DNA molecule is made up of one old strand and one new strand.

The other options are incorrect:

• Conservative replication would produce two new DNA molecules, each of which would be a copy of the original DNA molecule. This is not what happens in DNA replication.
• Dispersive replication would produce two new DNA molecules, each of which would be a mixture of old and new DNA. This is not what happens in DNA replication.

Answer: Transcription

Transcription is the process by which the information encoded in DNA is copied into RNA. RNA is a molecule that is similar to DNA, but it has a single strand instead of a double helix. RNA molecules are used to carry the genetic information from DNA to ribosomes, where they are translated into proteins.

The other options are incorrect:

• Translation is the process by which the information encoded in RNA is translated into amino acids, which are the building blocks of proteins.
• RNA splicing is the process by which the introns, or non-coding regions, of an RNA molecule are removed.
• Transposition is the process by which a segment of DNA is moved from one location to another in the genome.

Answer: Adenine

Nucleic acids contain adenine (A), guanine (G), cytosine (C), and thymine (T) in RNA and uracil (U) instead of thymine in DNA. These are the nitrogenous bases that make up the nucleotides of nucleic acids. Alanine, lysine, and arginine are amino acids, which are the building blocks of proteins.

Answer: Nucleotides

Nucleotides are linked together by covalent bonds between the phosphate group of one nucleotide and the sugar molecule of the next nucleotide. This creates a long chain of nucleotides, which is the basic structure of nucleic acids.

The other options are incorrect:

• N-bases are the nitrogenous bases that are found in nucleotides.
• Nucleosides are molecules that consist of a nitrogenous base and a sugar molecule.
• Histones are proteins that are found in the nucleus of cells and help to package DNA into chromatin.

Answer: RNA

The most important function of a gene is to synthesize RNA. Genes contain the instructions for making RNA, which is a molecule that is similar to DNA but has a single strand instead of a double helix. RNA molecules are used to carry the genetic information from DNA to ribosomes, where they are translated into proteins.

Enzymes are proteins that catalyze biochemical reactions. Hormones are signaling molecules that are produced by endocrine glands and regulate various physiological processes. DNA is a molecule that stores genetic information. While all of these molecules are important, the most fundamental function of a gene is to synthesize RNA.

Answer: Red-green colour baldness

Among the options provided, the gene present exclusively on the X-chromosome in humans is concerned with red-green color blindness. Red-green color blindness is an inherited condition that affects the ability to distinguish between red and green colors. It is caused by a mutation in one of the genes that codes for the proteins involved in color vision. These genes are located on the X chromosome, so males are more likely to be affected by color blindness than females.

The other options are not related to genes on the X chromosome:

• Baldness is a common condition that can be caused by a variety of factors, including genetics, aging, and certain medical conditions. There is no single gene that causes baldness, and it is not exclusively linked to the X chromosome.
• Facial hair/moustache in males is influenced by a combination of genetic and hormonal factors. The presence or absence of facial hair is not determined by a single gene, and it is not exclusive to the X chromosome.
• Night blindness is a condition that affects the ability to see in low light. It is caused by a variety of factors, including genetic mutations, vitamin A deficiency, and retinal damage. There is no single gene that causes night blindness, and it is not exclusively linked to the X chromosome.

Answer: Amino acids

Amino acids are organic molecules that contain an amino group (-NH2), a carboxyl group (-COOH), and a side chain (R group). Peptide linkages are formed when the carboxyl group of one amino acid reacts with the amino group of another amino acid, forming a covalent bond between the carbon atom of the carboxyl group and the nitrogen atom of the amino group. This reaction is known as a dehydration synthesis reaction, and it releases a molecule of water.

The other options are incorrect:

• Nucleotides are the structural units of nucleic acids, such as DNA and RNA. They are composed of a nitrogenous base, a sugar molecule, and a phosphate group.
• Glucose molecules are simple sugars that are the main source of energy for cells. They are composed of six carbon atoms, six oxygen atoms, and twelve hydrogen atoms.
• Sucrose is a disaccharide that is composed of one molecule of glucose and one molecule of fructose. It is a common table sugar.

Answer: RNA – (+) type

Poliovirus is an RNA virus, which means that its genetic material is stored in the form of RNA, not DNA. The RNA genome of poliovirus is a single-stranded molecule of positive polarity, which means that it can be directly translated into protein without the need for transcription into mRNA.

The other options are incorrect:

• DNA is the nucleic acid that stores genetic information in most organisms. It is a double-stranded molecule that is composed of two complementary strands of nucleotides.
• t-RNA (transfer RNA) is a type of RNA that is involved in protein translation. It carries amino acids to ribosomes, where they are incorporated into proteins.
• m-RNA (messenger RNA) is a type of RNA that carries the genetic information from DNA to ribosomes, where it is translated into protein.

Answer: Enveloped RNA virus

Enveloped viruses are surrounded by a lipid membrane that is derived from the host cell membrane. The lipid membrane helps the virus to enter and infect host cells. The RNA genome of rabies virus is negative-sense, which means that it must be transcribed into positive-sense RNA before it can be translated into protein.

The other options are incorrect:

• Naked RNA viruses do not have a lipid envelope. They are composed of a single strand of RNA that is surrounded by a protein coat.
• Naked DNA viruses do not have a lipid envelope. They are composed of a double strand of DNA that is surrounded by a protein coat.
• Enveloped DNA viruses are surrounded by a lipid membrane, but their genetic material is stored in the form of DNA, not RNA.

Answer: Adeno virus

Adenoviruses are a group of non-enveloped DNA viruses that can infect a wide range of hosts, including humans, animals, and birds. They are responsible for a variety of respiratory, gastrointestinal, and eye infections. Some adenoviruses can also cause cancer.

• Polio virus is an RNA virus that causes poliomyelitis, a paralytic disease.
• Echo virus is an RNA virus that belongs to the Picornaviridae family and is associated with aseptic meningitis and hand-foot-and-mouth disease.
• Poty virus is an RNA virus that belongs to the Potyviridae family and is a major plant pathogen.

Here are some other examples of DNA viruses:

• Herpes simplex virus (HSV)
• Hepatitis B virus (HBV)
• Human papillomavirus (HPV)
• Poxvirus

Answer: Restriction enzymes

Restriction enzymes are endonucleases that cleave DNA at specific sites. They are found in bacteria and archaea, and they play a role in protecting these organisms from bacteriophages (viruses that infect bacteria). Restriction enzymes are used in genetic engineering to cut DNA into fragments that can be manipulated and ligated together to create recombinant DNA molecules.

The other options are incorrect:

• Ligases are enzymes that join together fragments of DNA. They are used in genetic engineering to ligate fragments of DNA that have been cut by restriction enzymes.
• Nucleases are enzymes that break down nucleic acids, such as DNA and RNA. They are involved in a variety of cellular processes, including DNA replication, repair, and transcription.
• Hydralases are enzymes that catalyze the hydrolysis of chemical bonds. They are involved in a variety of cellular processes, including metabolism, signaling, and transport.

Answer: Transduction

The transfer of DNA from one bacterium to another through phages is termed as transduction. Transduction is a form of horizontal gene transfer, which is the transfer of genetic material between different organisms without the involvement of sexual reproduction.

The other options are incorrect:

• Induction is the process by which a prophage, a virus that is integrated into the bacterial chromosome, becomes active and produces new phages.
• Transfection is the introduction of foreign DNA into a eukaryotic cell, typically using a virus or other vector.
• Infection is the invasion of an organism by a pathogen, such as a virus or bacteria.

Answer: Pyruvic acid

Microorganisms usually make acetyl-CoA by oxidizing pyruvic acid. Pyruvic acid is a product of glycolysis, the process by which cells break down glucose to produce energy. Acetyl-CoA is a key intermediate in the citric acid cycle, a metabolic pathway that produces energy and building blocks for other molecules.

The other options are incorrect:

• Acetic acid is a product of fermentation, a process by which microorganisms break down glucose in the absence of oxygen. Acetic acid can be converted to acetyl-CoA, but this is not the usual pathway in microorganisms.
• α-ketoglutaric acid is an intermediate in the citric acid cycle, but it is not a direct source of acetyl-CoA.
• Fumaric acid is another intermediate in the citric acid cycle, but it is also not a direct source of acetyl-CoA.

Answer: Semi conservative

The method of DNA replication proposed by Watson and Crick is Semi-conservative. In the semi-conservative model, each strand of the parental DNA molecule serves as a template for the synthesis of a new, complementary strand. This results in two daughter DNA molecules, each consisting of one old (original) strand and one newly synthesized strand.

Answer: 34 Ao

DNA is a double helix, meaning that it is made up of two strands of nucleotides that are twisted around each other. Each turn of the helix contains 10 base pairs, and the distance between each base pair is 3.4 Å. Therefore, the distance between each turn of the helix is 10 base pairs × 3.4 Å/base pair = 34 Å.

The other options are incorrect:

• 20 Å is the diameter of the DNA helix.
• 28 Å is the distance between each base pair in RNA.
• 42 Å is the distance between each nucleotide in a single strand of DNA.

Answer: Proteins

Western blotting is a technique used to identify and quantify specific proteins in a sample. It is a widely used method in molecular biology and biochemistry.

The other options are incorrect:

• DNA: DNA is a nucleic acid that contains the genetic instructions for making proteins. It is not directly involved in protein synthesis.
• RNA: RNA is a nucleic acid that carries genetic information. It is not involved in protein synthesis.

Answer: Transcription

Transcription is the process of copying the genetic information from DNA to RNA. The RNA molecule that is produced is called messenger RNA (mRNA), and it carries the information that is needed to make a specific protein.

The other options are incorrect:

• Transformation is the process of transferring genetic material from one organism to another.
• Translation is the process of making a protein from mRNA.
• Replication is the process of copying DNA from one molecule to another.

Answer: Protein

Western blotting is a technique used in the determination of proteins. It involves the separation of proteins based on size through gel electrophoresis, transferring them to a membrane, and then using specific antibodies to detect the target protein.

The other options are incorrect:

• DNA: Western blotting is not used for the determination of DNA. Techniques like Southern blotting are more appropriate for DNA analysis.
• RNA: Western blotting is not designed for the determination of RNA. Other techniques, such as Northern blotting, are more suitable for RNA analysis.
• Polysaccharides: Western blotting is not typically used for the determination of polysaccharides. It is primarily focused on proteins. Techniques like lectin blotting may be more suitable for studying polysaccharides.

Answer: Nucleotides

The building blocks of nucleic acids are nucleotides. A nucleotide is composed of a phosphate group, a sugar molecule (ribose in the case of RNA and deoxyribose in the case of DNA), and a nitrogenous base (adenine, thymine, cytosine, or guanine).

The other options are incorrect:

• Amino acids are the building blocks of proteins.
• Nucleosides are composed of a nitrogenous base and a pentose sugar. They are not phosphorylated.
• Nucleo proteins are complexes of nucleic acids and proteins.

Answer: Repetitive sequences

DNA fingerprinting is based on repetitive sequences of DNA. These sequences are also known as variable number tandem repeats (VNTRs) or short tandem repeats (STRs). They are found throughout the genome and vary in length from person to person.

The other options are incorrect:

• Unique sequences of DNA are not common enough to be used for DNA fingerprinting.
• Amplified sequences of DNA are used in other techniques, such as PCR, but not in DNA fingerprinting.
• Non-coding sequences of DNA do not code for proteins, and therefore do not vary in length from person to person.

Answer: Reverse transcriptase

The enzyme required for synthesizing DNA from an RNA template is reverse transcriptase. Reverse transcriptase is capable of catalyzing the reverse transcription process, where a complementary DNA (cDNA) strand is synthesized from a single-stranded RNA template. This enzyme is often used in techniques like reverse transcription polymerase chain reaction (RT-PCR) to convert RNA into DNA for further analysis.

The other options are incorrect:

• RNA polymerase is an enzyme that synthesizes RNA from a DNA template.
• DNA polymerase is an enzyme that synthesizes DNA from a DNA template.
• Terminal transferase is an enzyme that adds nucleotides to the ends of DNA molecules.

Answer: Reo virus

Retroviruses are a type of virus that contains RNA as their genetic material. When a retrovirus infects a cell, it uses its reverse transcriptase enzyme to convert its RNA genome into DNA. This DNA is then integrated into the host cell’s DNA, where it can be transcribed into RNA and used to make new viral particles.

The other options are incorrect:

• Rhabdo virus: Rhabdoviruses have single-stranded, negative-sense RNA genomes. They do not possess a double-stranded RNA genome.
• Parvo virus: Brief: Parvoviruses have single-stranded DNA genomes. They do not contain double-stranded RNA.
• Retro virus: Brief: Retroviruses have single-stranded, positive-sense RNA genomes. They are unique in their ability to reverse transcribe their RNA genome into DNA, but they do not naturally have a double-stranded RNA genome.

Answer: All of the above

All of the options provided are examples of DNA viruses:

• Adeno virus: Adenoviruses are a group of DNA viruses that can infect various tissues, including the respiratory and gastrointestinal tracts.
• Bacteriophage T1, T2, T3, T4, T5, T6: Bacteriophages, including T1, T2, T3, T4, T5, T6, are viruses that infect bacteria. They have DNA genomes.
• Papova virus: Papovaviruses, including the human papillomavirus (HPV) and the polyomavirus, are DNA viruses.
• Herpes virus and cauliflower mosaic:Herpesviruses, such as the herpes simplex virus, and Cauliflower mosaic virus are examples of DNA viruses. Herpesviruses infect animals, while Cauliflower mosaic virus infects plants.

Answer: Bacteriophage Φ C

Bacteriophage Φ C is a bacteriophage, which means it infects bacteria and has a DNA genome. Bacteriophages are not RNA viruses; they are viruses with DNA genomes that infect bacterial cells.

The other options are all correct:

• Reoviruses are double-stranded RNA viruses that can cause respiratory infections and diarrhea.
• Retroviruses are single-stranded RNA viruses that can cause diseases such as HIV/AIDS.
• Tmv and Bacteriophages Ms2, F2 are all single-stranded RNA viruses. Tmv is a plant virus that causes tobacco mosaic disease, and bacteriophages Ms2 and F2 are bacterial viruses.
• Dahila mosaic virus and Bacteriophages Φ × 174, M12, M13 are all single-stranded DNA viruses. Dahila mosaic virus is a plant virus that causes yellowing and stunting of dahlia plants, and bacteriophages Φ × 174, M12, and M13 are bacterial viruses.

Answer: Hydrogen bonds between bases

Hydrogen bonds are weak interactions between atoms that have a partial positive charge (hydrogen) and atoms that have a partial negative charge (oxygen or nitrogen). In DNA, the hydrogen bonds form between the complementary bases adenine (A) and thymine (T), and cytosine (C) and guanine (G).

The other options are incorrect:

• Ionic bonds are formed between atoms with opposite charges. They are strong bonds that are not found in DNA.
• Covalent bonds are formed between atoms that share electrons. They are also strong bonds that are not found in DNA.
• Polar charges are the result of uneven distribution of electrons in a molecule. They can influence hydrogen bonding, but they do not directly join the two strands of DNA.

Answer: Double hydrogen bonds

In DNA, adenine (A) always pairs with thymine (T) through two hydrogen bonds. This specific pairing is essential for the structure and function of DNA. The double hydrogen bonds between A and T help to stabilize the DNA double helix and ensure that the genetic information is accurately replicated.

The other options are incorrect:

• Triple hydrogen bonds are formed between cytosine (C) and guanine (G), not between A and T.
• Single hydrogen bonds are not strong enough to hold the two strands of DNA together.

Answer: 34 Ao

Ångströms (Å) are a unit of length commonly used in molecular biology to measure the size of molecules, such as DNA and RNA. One Ångström is equal to 0.1 nanometers (nm).

The DNA double helix consists of two strands of DNA that are twisted together in a spiral shape. Each coil of the helix is 34 Å long and contains 10.5 base pairs. The distance between two consecutive base pairs is 0.34 nm.

The other options are incorrect:

• 15 Å is the distance between two consecutive base pairs in DNA.
• 30 Å is an approximate length of a single base pair in DNA.
• 5 Å is too small to be the length of a coil in DNA.

Answer: There is phosphodiester bond between 5’- hydroxyl of one ribose and 3’–hydroxyl of next ribose

Nucleic acids are highly charged polymers due to the presence of phosphodiester bonds. The phosphodiester bond connects the 5′-phosphate group of one nucleotide to the 3′-hydroxyl group of the next nucleotide in the chain. The negatively charged phosphate groups along the backbone of the nucleic acid contribute to its overall negative charge. The other options are not accurate explanations for the high charge of nucleic acids.

The other options are incorrect:

• They have positive and negative ends: This statement is not accurate. Nucleic acids have a consistent negative charge along their entire length due to the negatively charged phosphate groups in the phosphodiester backbone.
• Nucleotides are charged structures: While individual nucleotides can carry a charge due to the phosphate group, the overall charge of the nucleic acid is attributed to the continuous negatively charged phosphodiester backbone.
• Nitrogenous bases are highly ionized compounds: Nitrogenous bases are not highly ionized. The charge in nucleic acids primarily comes from the phosphate groups in the backbone, not the bases. The bases are involved in hydrogen bonding and base pairing but do not contribute significantly to the overall charge.

Answer: Genome

A genome is the complete set of genetic material in an organism. It is made up of DNA and contains the information needed to build and maintain an organism. The number of genes in a genome varies widely from organism to organism. For example, the human genome has about 20,000 genes, while the Escherichia coli bacterium has only about 4,000 genes.

The other options are incorrect:

• A gene map is a diagram that shows the location of genes on a chromosome.
• Gene structure refers to the organization of a gene, including its promoter, coding region, and terminator.
• Chromatin is the material that DNA is packaged into in the nucleus of a cell. It is made up of DNA, proteins, and RNA.

Answer: A few no. of genes are transferred

This is because specialized transduction is a process in which only a small portion of the bacterial chromosome is transferred to a new host. This portion of DNA typically includes a few genes that are located near the prophage, which is the integrated form of the bacteriophage.

The other options are incorrect:

• Large amounts of DNA are not transferred during specialized transduction.
• Whole DNA is not transferred during specialized transduction.
• Specialized transduction is a specific type of transduction that occurs when a bacteriophage incorrectly excises its DNA from the bacterial chromosome. This excised DNA can then be packaged into new phage particles and transferred to a new host. Only a small portion of the bacterial chromosome is transferred during this process.

Answer: Exogenate

Transformation is a process in which a cell takes up foreign DNA from the surrounding environment. The cell that donates the DNA is called the exogenate, while the cell that receives the DNA is called the recipient. Exogenous DNA can come from a variety of sources, including bacteria, viruses, and plasmids.

The other options are incorrect:

• Endogenate refers to DNA that is native to an organism.
• Mesozygote refers to an organism that is heterozygous for a particular gene.
• Merosite is a part of a zygote that does not contribute to the formation of the embryo.

Answer: Transcriptase

The process of transferring genetic information from DNA to RNA is called transcription. The enzyme responsible for this process is called RNA polymerase, and the resulting RNA molecule is known as messenger RNA (mRNA).

The other options are incorrect:

• Transduction is the process by which bacterial DNA is transferred from one bacterium to another by a bacteriophage.
• Transformation is the process by which a cell takes up foreign DNA from the surrounding environment.
• Recombination is the process by which genetic information is exchanged between two homologous chromosomes.

Answer: All of the above

Gene transfer can occur through various mechanisms in different organisms:

• Transformation: In transformation, genetic material is taken up by a cell from its environment. This process is often observed in bacteria.
• Transduction: Transduction involves the transfer of genetic material from one cell to another via a virus (bacteriophage) that acts as a vector.
• Conjugation: Conjugation is the direct transfer of genetic material from one bacterial cell to another through physical contact, often mediated by a plasmid.
• Cell fusion: Cell fusion refers to the merging of two cells, allowing their contents, including genetic material, to combine. This process can occur in various contexts, such as in the formation of multicellular organisms.

Answer: HBV

Serum hepatitis is commonly associated with Hepatitis B virus (HBV). Hepatitis B is a viral infection that can lead to inflammation of the liver, and it is transmitted through contact with the blood or other body fluids of an infected person

The other options are incorrect:

• HCV stands for hepatitis C virus. HCV is a type of liver infection that is typically spread through blood-to-blood contact.
• HAV stands for hepatitis A virus. HAV is a type of liver infection that is typically spread through contaminated food or water.
• HIV stands for human immunodeficiency virus. HIV is a virus that attacks the immune system.

Answer: IgM

Immunoglobulin M (IgM) is the first antibody produced by the immune system in response to an infection. It is a large, pentameric molecule that is very efficient at activating the complement system, which is a group of proteins that help to destroy pathogens. IgM is also very effective at agglutinating, or clumping together, pathogens, which makes it easier for them to be phagocytosed, or engulfed, by immune cells.

The other options are incorrect:

• IgE is an antibody that is involved in allergic reactions.
• IgA is an antibody that is found in mucosal secretions, such as saliva, tears, and breast milk. It helps to protect the body from pathogens that enter the body through these routes.
• IgG is the most abundant antibody in the blood. It is involved in long-term immunity.

Answer: Non-immunogenic

Haptens are molecules that, by themselves, are non-immunogenic, meaning they cannot elicit an immune response. However, when haptens bind to larger carrier molecules (usually proteins), they can become antigenic. The combination of a hapten and a carrier molecule forms a complete antigen, capable of eliciting an immune response.

The other options are incorrect:

• Immunogenic: Haptens, in their standalone form, are typically non-immunogenic. They require coupling to a carrier molecule to become immunogenic.
• Antigenic: Haptens are not antigenic by themselves. They become part of an antigenic structure when bound to a carrier molecule.

Answer: IgM

IgM is the largest and heaviest of the antibodies, and it is the first antibody to be produced in response to an infection. It is a pentameric molecule, meaning that it is made up of five Y-shaped subunits. This gives it a large surface area, which allows it to bind to multiple antigens at the same time. IgM is also very efficient at activating the complement system, which is a group of proteins that help to destroy pathogens.

The other options are incorrect:

• IgG is the most abundant antibody in the blood, and it is responsible for long-term immunity.
• IgD is a minor antibody that is found on the surface of B cells. It is involved in the activation of B cells.
• IgE is an antibody that is involved in allergic reactions.

Answer: B-lymphocytes

B-lymphocytes, also known as B cells, are a type of white blood cell that is responsible for producing antibodies. When a B cell encounters an antigen, a foreign substance that the body does not recognize, it becomes activated and begins to divide. The daughter cells of the activated B cell, called plasma cells, are responsible for producing antibodies. Antibodies are proteins that bind to antigens and help to mark them for destruction by other immune cells.

The other options are incorrect:

• T-lymphocytes, also known as T cells, are another type of white blood cell that is responsible for helping to kill infected cells and cancer cells.
• Monocytes are a type of white blood cell that is responsible for engulfing and destroying foreign substances.
• RBCs, or red blood cells, are responsible for carrying oxygen from the lungs to the rest of the body. They do not play a role in the immune system.

Answer: Chiasmata

Chiasmata are X-shaped structures that form during meiosis I when homologous chromosomes exchange segments of DNA. These sites of crossing over are visible under a microscope and are an indication that crossing over has occurred.

The other options are incorrect:

• Synaptonemal complex is a protein structure that holds homologous chromosomes together during meiosis I.
• Centromeres are the points where sister chromatids are attached to each other.
• Protein axes are the protein filaments that make up the framework of the chromosomes.

Answer: 8%

The normal concentration of globulin in human serum is approximately 8%. Globulins are a group of proteins in the blood that include antibodies, enzymes, and other proteins involved in immune and transport functions. The total protein in human serum is composed of albumin and globulins, with globulins making up about 8% of the total.

The other options are incorrect:

• 12%: This percentage is higher than the typical concentration of globulins in human serum.
• 16%: This percentage is higher than the typical concentration of globulins in human serum.
• 4%: This percentage is lower than the typical concentration of globulins in human serum.

Answer: Inhibitor

Antimetabolites are a type of inhibitor that compete with normal metabolites for active sites on enzymes. As a result, they prevent the enzyme from carrying out its normal function. Antimetabolites can be used as drugs to treat cancer and other diseases.

The other options are incorrect:

• Activators are substances that increase the activity of an enzyme.
• Substrates are the molecules that an enzyme acts on.
• Cofactors are non-protein molecules that are required for the activity of an enzyme.