Category: Life Sciences Objective Questions

Life Sciences Multiple Choice Questions on “Major Histocompatibility Complex”.

1. Major Histocompatibility Complex is a tight cluster of linked___________
A. Carbohydrates
B. Proteins
C. Genes
D. Lipid molecules
Answer: C
Clarification: MHC is polygenic in nature, i.e. several genes control the expression of the MHC molecule. These are cell surface proteins which are present with peptide on antigen presenting cells.

2. What is the name of MHC in humans?
A. HLA
B. H2
C. Adjuvants
D. Haplotype
Answer: A
Clarification: Genes for MHC are located on the short arm of chromosome 6 in humans. In human, it is also known as human leukocyte antigens (HLA). MHC is glycoproteins which are expressed on all nucleated cells.

3. All the individual of the same species has the same allele of MHC genes.
A. True
B. False
Answer: B
Clarification: MHC is polymorphic in nature and shows genetic polymorphism by expressing different alleles of a gene. Different individuals have different types of MHC genes. MHC genes are expressed as codominantly.

4. Which of the following polypeptide is important for the expression of MHC I on the cell membrane?
A. Interferons
B. β₂-microglobin
C. Lymphokines
D. Interleukins
Answer: B
Clarification: β₂-microglobin is encoded by chromosome 15, it is always attached to α₃ subunit of MHC I molecules through non-covalent interactions. It does not have a tail.

5. Which of these are non-professional antigen presenting cells?
A. Macrophages
B. Dendritic cells
C. Fibroblast
D. B lymphocytes
Answer: C
Clarification: Antigen presenting cells (APC. is of two types i.e. professional and non-professional antigen presenting cells. Professional antigen presenting cells are B-lymphocytes, dendritic cells, and macrophages while non-professional APCs are fibroblast, epithelial cells, glial cells etc.

6. Name the cell which receives antigen presented by MHC molecule.
A. Nk cells
B. B-cells
C. T-cells
D. Macrophages
Answer: C
Clarification: MHC molecules present processed antigen to T-cells as T-cell receptor does not recognize free antigen, it will recognize only those antigens which are bound to MHC molecules.

7. Name the class of MHC which is recognized by CD4 TH cell.
A. MHC cannot recognize T cells
B. MHC III
C. MHC I
D. MHC II
Answer: D
Clarification: CD4 is a monomeric single chain which recognizes MHC II molecule and is present on T helper cell. It consists of a core extracellular domain and has three critical serine residues on a cytoplasmic tail.

8. Which MHC molecule recognizes CD8 TC cells?
A. MHC I
B. MHC II
C. MHC III
D. HLA-C
Answer: A
Clarification: CD8 is a co-receptor of T-cell and is present on the T cytosolic cell. It is a hetrodimer of α and β chains and recognizes MHC I molecule.

9. Name the part of processed antigen that binds to the MHC molecule and recognized by T-cells?
A. Immunoglobulin
B. Agretope
C. Epitope
D. Chaperone
Answer: B
Clarification: Agretope is the part of processed antigen that is attached to MHC molecule and exposed to T-cell.

10. Which of the following statement is INCORRECT about superantigens?
A. Viral or bacterial proteins
B. Endogenous by nature
C. Unique binding ability
D. Activate a large number of T-cells
Answer: B
Clarification: Superantigens are viral or bacterial proteins which have the unique binding ability of T-cell receptor and MHC II molecules, i.e. it binds simultaneously to both and activate large numbers of T-cells. It can be both either endogenous or exogenous in nature.

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Life Sciences Multiple Choice Questions on “DNA Replication”.

1. Double-helix structure of DNA is discovered by___________
A. Gobind Khurana
B. Nirenberg
C. Watson and Crick
D. Darwin
Answer: C
Clarification: In 1953, Watson and Crick worked out on the double – helix structure of DNA and find out the complementary nature of two strands.

2. Base sequence of each parental strand considered to synthesis new complementary strand.
A. True
B. False
Answer: A
Clarification: The two strands of DNA are separated without breakage of a covalent bond and its base sequence act as the template strand to synthesize a new complementary strand.

3. What is a mode of replication in E.coli?
A. Intermediate
B. Dispersive
C. Conservative
D. Semiconservative
Answer: D
Clarification: Meselson and Stahl in 1958 conducted an experiment and demonstrated the semiconservative replication of DNA in E.coli.

4. What is the origin of replication?
A. Particular site at which DNA replication starts
B. Site which prevents initiation
C. Random location on the DNA
D. Site at which replication terminated
Answer: A
Clarification: Origin of replication is particular sites on DNA as replication does not start at random sites. Replication starts from a particular site and proceeds bidirectionally or unidirectionally till the terminus site.

5. How many numbers of replicon is found in E.coli?
A. Five replicon
B. Two replicon
C. Single replicon
D. Multiple replicon
Answer: C
Clarification: E.coli is monorepliconic and have single replicon while eukaryotic cells contain many replication origins on a single chromosome and called multirepliconic.

6. Which of the following protein does not involve in the initiation of replication?
A. DnaA
B. SSB (Single strand binding protein)
C. DnaB
D. DnaF
Answer: D
Clarification: In eukaryotic replication, more than 20 proteins take part out of that the initiation of replication takes place in the presence of helicase, primase, SSB, DnaC, DnaA.

7. Which of the following protein is required for connecting Okazaki fragments?
A. Scaffold protein
B. Helicase
C. Primase
D. DNA gyrase
Answer: D
Clarification: After initiation, the chain elongation and joining of Okazaki fragments take place by DNA gyrase, DNA ligase, DNA polymerase.

8. Name the protein, which is used for termination of replication?
A. DnaC
B. SSB
C. Tus protein
D. DNA polymerase
Answer: C
Clarification: Tus protein is terminus binding protein which is used for termination of replication.

9. Which of the following would relax negatively supercoiled DNA?
A. DNA gyrase
B. Type I topoisomerase
C. Collagen
D. Elastin
Answer: B
Clarification: Negatively supercoiled DNA can be relaxed by topoisomerase I. It creates the nick in one strand of DNA and rotates freely to resolve supercoiling.

10. Name the protein, which is responsible for the formation of RNA primer?
A. Topoisomerase
B. Gyrase
C. Helicase
D. Primase
Answer: D
Clarification: RNA primers are generated by using protein, primase which is also known as RNA polymerase. Primers are short RNA sequences.

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Life Sciences Multiple Choice Questions on “Enzymes – 1”.

1. A __________is a biocatalyst that increases the rate of the reaction without being changed.
A. Aluminum oxide
B. Silicon dioxide
C. Enzyme
D. Hydrogen peroxide
Answer: C
Clarification: Among these options, an enzyme is an only option which is a biocatalyst that catalyzes the chemical reaction without being changed while all other options are of the catalyst which increases or decrease the rate of reaction based on their concentration.

2. Enzyme increases the rate of reaction by lowering the activation energy.
A. True
B. False
Answer: A
Clarification: Activation energy is the difference in free energy between the reactants and transition state. To complete a reaction, enzyme lowers the activation energy and crosses the transition state.

3. What is the nature of an enzyme?
A. Vitamin
B. Lipid
C. Carbohydrate
D. Protein
Answer: D
Clarification: All enzymes are protein except Catalytic RNA molecule. The native protein conformation of an enzyme defines its catalytic activity. Once the enzyme is denatured, its catalytic activity is also lost.

4. What is an apoenzyme?
A. It is a protein portion of an enzyme
B. It is a non-protein group
C. It is a complete, biologically active conjugated enzyme
D. It is a prosthetic group
Answer: A
Clarification: Removal of cofactor from a conjugated enzymes forms apoenzyme which is a protein component. A cofactor is a non-protein group while a complete conjugated enzyme is known as a holoenzyme.

5. Name the coenzyme of riboflavin (B2)?
A. NAD or NADP
B. FAD and FMN
C. Coenzyme A
D. Thiamine pyrophosphate
Answer: B
Clarification: Riboflavin is a part of vitamin B complex, its coenzyme form is a FAD (Flavin adenine dinucleotide) which involves a redox reaction. NAD is a coenzyme form of nicotinic acid, and thiamine pyrophosphate is a coenzyme of thiamine.

6. Which of this vitamin is associated with the coenzyme Biocytin?
A. Nicotinic acid
B. Thiamine
C. Biotin
D. Pyridoxine
Answer: C
Clarification: Biocytin is a coenzyme of biotin which involves in carboxylation reaction while thiamine takes part in decarboxylation reaction.

7. Name the enzyme secreted by pancreas?
A. Pepsin
B. Chymotrypsin
C. Trypsin
D. Alcohol dehydrogenase
Answer: C
Clarification: Trypsin is a proteolytic enzyme, secreted by the pancreas. It is one of the three digestive proteinases along with pepsin and chymotrypsin which breaks down dietary protein molecules into simpler forms.

8. Name the enzyme which catalyzes the oxidation-reduction reaction?
A. Transaminase
B. Glutamine synthetase
C. Phosphofructokinase
D. Oxidoreductase
Answer: D
Clarification: Oxidoreductase is a class of enzyme which catalyze the oxidation-reduction reaction. Some of the oxidoreductase enzymes are oxidases, dehydrogenases, peroxidases etc.

9. What is the function of phosphorylase?
A. Transfer inorganic phosphate
B. Transfer a carboxylate group
C. Use H₂O₂ as the electron acceptor
D. Transfer amino group
Answer: A
Clarification: Phosphorylase is a transferase enzyme which involves a transfer of inorganic phosphate to a substrate while transcarboxylase transfer a carboxylate group and transaminase transfer amino group from amino acid to the keto acid.

10. Mark the CORRECT function of enzyme, Peptidase?
A. Cleave phosphodiester bond
B. Cleave amino bonds
C. Remove phosphate from a substrate
D. Removal of H₂O
Answer: B
Clarification: Hydrolases are the enzymes which cleave the bond by adding water. Peptidases belong to hydrolase class and it is used to cleave amide bonds of proteins.

11. Which of the following reaction is catalyzed by Lyase?
A. Breaking of bonds
B. Formation of bonds
C. Intramolecular rearrangement of bonds
D. Transfer of group from one molecule to another
Answer: A
Clarification: Lyase is the class of enzymes which does not involve hydrolysis or oxidation to break the bond. It catalyzes the breaking of C-C, C-O, C-N, C-S bonds by the process of elimination and results in the formation of a double bond.

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Life Sciences Multiple Choice Questions on “Golgi Complex”.

1. Name the scientist who discovered Golgi apparatus?
A. Robert Remake
B. Rudolf Virchow
C. Camillo Golgi
D. Theodor Schwann
Answer: C
Clarification: Camillo Golgi was an Italian physician who first discovered Golgi complex, which is a single membrane-bound organelle. It consists of five to eight membrane-bound sacs called cisternae.

2. Golgi stack is the stack of Golgi cisternae.
A. True
B. False
Answer: A
Clarification: Golgi stack or dictyosome is the stack of flattened membrane bound sacs called cisternae. The cisternae in stack vary in number, shape, and organization and represented as cis, medial and transform.

3. Which of the following organelle takes part in the secretion?
A. Cytoplasm
B. Ribosomes
C. ER compartments
D. Golgi apparatus
Answer: D
Clarification: Golgi apparatus is prominent in cells that are specialized for secretion like goblet cell of intestinal epithelium secrete a large amount of mucus. Cell secretion takes place from trans-Golgi through exocytosis.

4. The chemical products of the cell are shipped and distributed by_______
A. ER lumen
B. Golgi apparatus
C. Lysosome
D. Endosome
Answer: B
Clarification: Golgi apparatus modifies and transport proteins and lipids that have been built in the endoplasmic reticulum to the outside of the cell or to other locations in the cell.

5. Which type of glycosylation takes place in the g=Golgi apparatus?
A. T-linked glycosylation
B. N-linked glycosylation
C. O-linked glycosylation
D. G-glycosylation
Answer: C
Clarification: O-linked glycosylation occurs by the linking of O-linked oligosaccharides to the hydroxyl group of amino acid via N-acetylglucosamine. Proteins undergo O-linked glycosylation in the cisternae of Golgi.

6. Which of the following is not the function of the Golgi apparatus?
A. Processing and shorting of glycoprotein
B. Lipid metabolism
C. Carbohydrate metabolism
D. Amino acid metabolism
Answer: D
Clarification: Golgi apparatus involves the metabolism of carbohydrates, and lipids, but not of amino acid, so, amino acid metabolism is incorrect. Synthesis of glycolipids and sorting of glycoprotein also takes place in Golgi apparatus.

7. Name the complex polysaccharide which does not synthesize in the Golgi apparatus?
A. Starch
B. Hemicellulose
C. Glycosaminoglycans
D. Pectins
Answer: A
Clarification: Complex polysaccharides are also synthesized in the Golgi apparatus such as hemicellulose and pectin in the cell wall of plant and glycosaminoglycans in the extracellular matrix of animals.

8. Which of the following hypothesis explain vesicle fusion?
A. Lipid raft hypothesis
B. SNARE hypothesis
C. Cell adhesion hypothesis
D. Cell kill hypothesis
Answer: B
Clarification: Snare hypothesis explains the vesicle fusion with target mediated by the interaction of specific proteins called SNAREs (Snape receptors). V-SNARE is present on vesicle while t-SNARE is present on the target.

9. Name the GTPase which control the recognition of interactions between v-SNARE and t-SNARE?
A. Rac protein
B. Ras protein
C. Rab protein
D. Rho protein
Answer: C
Clarification: Rab protein attached with the surface of the vesicle; when vesicle encounter with target membrane, the binding of v-SNARE and t-SNARE causes vesicle to bound the membrane and allow the Rab protein to hydrolyze its bound GTP.

10. Which of the following ATPase dissociate SNARE apart?
A. V-ATPase
B. F-ATPase
C. P-ATPase
D. NSF
Answer: D
Clarification: Once the vesicle fusion to target membrane is done, the complex dissociates with the help of NSF (NEM sensitive factor), which is a soluble ATPase that hydrolyses ATP and separate SNAREs.

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Life Sciences Multiple Choice Questions on “Immunoglobulins”.

1. Synthesis of antibodies takes place by which of the following cells?
A. Bone marrow cells
B. T-cells
C. B-cells
D. Lymph
Answer: C
Clarification: Antibodies are also called immunoglobulin, the antigen- binding glycoproteins, which are exclusively synthesized by B-cells and in billions of forms with different amino acid sequences and different antigen binding sites.

2. The basic structure of antibodies are______
A. Y-shaped
B. X-shaped
C. Linear
D. Hyperbolic
Answer: A
Clarification: The simple antibody structure has two identical antigen-binding sites forming a Y-shaped molecule. These antigen-binding sites are present on the tip of each arm of the Y.

3. Name the heavy chain of immunoglobulin G.
A. μ
B. ε
C. α
D. γ
Answer: D
Clarification: Immunoglobulin has five isotopes with different heavy chains, i.e. IgM has a μ heavy chain, IgE has ε, IgA has α, and IgG has a γ heavy chain.

4. What is the name of the hypervariable region of immunoglobin, which is responsible for its diversity?
A. CDR
B. Hinge region
C. Epitope
D. Agretope
Answer: A
Clarification: CDR is complementarity determining regions which impart the diversity in the variable region of both heavy and light chains. These are three small hypervariable regions and remaining part is called framework region.

5. Who discovered the structure of immunoglobulin by treating it with beta-mercaptoethanol?
A. Nisonoff
B. Edelman
C. Porter
D. Whittekar
Answer: B
Clarification: Edelman discovered that when immunoglobulin treated with beta-mercaptoethanol, it will fall apart into four chains, i.e. two identical light chain and two large heavy chains. This result was considered to propose a structure of immunoglobulin.

6. Which of the following amino acid is found in the hinge region?
A. Alanine
B. Aspargine
C. Proline and cysteine
D. Phenylalanine
Answer: C
Clarification: Hinge region is found in IgG, IgA, and IgD to provide flexibility in its structure. These regions are rich in proline and cysteine and basically found between two Fab arms of the Y-shaped antibody.

7. Which immunoglobulin can pass through placenta?
A. IgD
B. IgE
C. IgM
D. IgG
Answer: D
Clarification: IgG is the only antibody which can pass through the placenta, except IgG2 all other subtypes of IgG can cross the placenta and transfer immunity from mother to fetus.

8. Name the class of immunoglobulin which has a pentameric structure?
A. IgE
B. IgG
C. IgA
D. IgM
Answer: D
Clarification: IgM is the first antibody to produce during the primary response to antigen and it is also the first antibody which is made by the developing B-cells. It is composed of five units and formed pentameric structure with a J-chain.

9. Which of these immunoglobulins is present in external secretion?
A. IgG
B. IgM
C. IgA
D. IgE
Answer: C
Clarification: IgA is the predominant immunoglobulin which is present in the external secretion such as saliva, breast feed, tears, and mucus. It constitutes 10-15% of total immunoglobin in serum.

10. Name the class of immunoglobulin which takes part in hypersensitivity reaction?
A. IgG
B. IgE
C. IgA
D. IgM
Answer: B
Clarification: IgE mediates hypersensitivity reaction which is responsible for the symptoms of hay fever, asthma, and anaphylactic shock. It includes degranulation of basophils and mast cells.

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Life Sciences Multiple Choice Questions on “Recombination”.

1. Rearrangement of DNA that involves the breakage and reunion of DNA is called___________
A. Replication
B. Recombination
C. Translation
D. Transcription
Answer: B
Clarification: Recombination is the process of rearrangement of DNA of breakage and reunion and it can change the genomic configuration.

2. Recombination is responsible for crossing-over during meiosis of eukaryotic cells.
A. True
B. False
Answer: A
Clarification: Recombination was first recognized as the process which is responsible for crossing over in the meiosis. It is a large scale rearrangement of DNA molecules.

3. Which of the following is NOT true about homologous recombination?
A. Exchange of homologous segments
B. Exchange takes place between two homologous DNA molecules
C. It is also termed as general recombination
D. It involves a direct exchange of sequences of DNA
Answer: D
Clarification: Homologous recombination involves a reciprocal exchange of sequences of DNA.

4. Which of the following is site specific recombination?
A. Modification
B. Transposition
C. Holiday junction
D. Retrotransposons
Answer:b
Clarification: Transposition is the process of recombination, which allows one DNA sequence to inserted in another without taking care of sequence homology.

5. Who proposed holiday model for homologous recombination?
A. Gobind Khurana
B. Louis Pasteur
C. Robin Holiday
D. Niels Bohr
Answer: C
Clarification: Robin Holiday in 1964, proposed an appealing scheme for recombination called holiday model or hetroduplex model.

6. Which of the following is NOT a recombination system?
A. RecBCD
B. RecE
C. RecF
D. DnaF
Answer: D
Clarification: Homologous recombination was first described in bacterial systems. The three different recombination systems are RecF, RecE, and RecBCD.

7. Name the phenomenon of allele replacement during recombination and DNA repair?
A. Replication
B. Mutation
C. Transversion
D. Gene conversion
Answer: D
Clarification: Gene conversion is the phenomenon of changing allele forms during recombination and DNA repair.

8. Name the protein, which is involved in homologous recombination in E.coli?
A. Topoisomerase
B. Gyrase
C. Helicase
D. RecBCD enzyme
Answer: D
Clarification: The three different recombination systems are RecF, RecE, and RecBCD. RecBCD is known as Exonuclease V and it has both helicase and nuclease activity.

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