Category: Life Sciences Objective Questions

250+ TOP MCQs on Gene Interaction and Answers

Life Sciences Multiple Choice Questions on “Gene Interaction”.

1. The Phenomenon of two or more than two genes affecting the expression of each other is called ___________
A. Crossing over
B. Pairing
C. Gene interaction
D. Linkage
Answer: C
Clarification: Mendel described every character is influenced by the particular expression of the gene, but when the characters are controlled by the combination of more than one gene, called gene interaction.

2. Which of the following ratio shows complementary gene interaction?
A. 9:7
B. 15:1
C. 1:2:1
D. 9:3:3:1
Answer: A
Clarification: Complementary gene interaction is first discovered by William Bateson and Reginald Punette in 1906. 9:7 ratio shows the 9 offspring have both dominant genes, while 7 is having either one dominant or both recessive.

3. Which of the following does not show Mendel’s law of inheritance?
A. Masking gene interaction
B. Epistasis
C. Supplementary gene interaction
D. Codominance
Answer: D
Clarification: Codominance is the phenomenon where both the alleles of the gene pair in a heterozygote are expressed and resulting in offspring which is neither dominant nor recessive. Example: AB blood group.

4. Crossing of two white flowers gives a colored flower, this shows complementary gene interaction.
A. True
B. False
Answer: A
Clarification: Two true varieties of white flowered plant crossed and result in purple color progeny which shows that there must be some enzyme secreted by both the dominant alleles which contributed in the color of the flowers.

5. What is epistasis?
A. Type of linkage
B. Masking or modifying gene effect
C. Upper portion of a chromosome
D. Group of genes
Answer: B
Clarification: It is a non-allelic suppression which involves two pairs of alleles. It can suppress both dominant or recessive alleles.

6. Which of the following is NOT the type of epistasis?
A. Dominant
B. Recessive
C. Collabrative
D. Supplementary
Answer: C
Clarification: Epistasis can be of many types based on the ability of an allele in masking and modification of gene effects. It can be of dominant, recessive, complementary or supplementary.

7. Choose the correct ratio, which shows the masking gene interaction?
A. 12:3:1
B. 9:3:4
C. 1:2:1
D. 9:7
Answer: A
Clarification: Masking gene interaction is also recognized as dominant epistasis. Here, dominant allele of one gene can mask the effect of either allele of the second gene.

8. Name the phenomenon where two genes have the same expression of the character?
A. Pleiotropy
B. Phenocopy
C. Penetrance
D. Expressivity
Answer: A
Clarification: Pleiotropy is the condition where either a single gene has multiple functions in the body or two genes have the same expression of the single character.

9. What is psudoallele?
A. Allele with similar function
B. Allele with similar structure
C. Alleles with similar function and structure
D. Alleles with similar function and different structure
Answer: D
Clarification: When two types of allele have similar functions but different structures, it is called pseudoallele. These genes located in close proximity.

10. Name the effect which shows the change in expression of alleles of the gene due to a specific environmental condition.
A. Pleiotropy
B. Linkage
C. Phenocopy
D. Penetrance
Answer: C
Clarification: It is a type of phenotypic variation where a single trait of an organism is usually changed due to environmental effects. This is not a hereditary effect when environmental conditions removed it goes back to normal.

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250+ TOP MCQs on Protein Folding and Answers

Life Sciences Multiple Choice Questions on “Protein Folding”.

1. Protein folding is a process in which a polypeptide folds in to ___________
A. 2-D structure
B. Globular form
C. 3-D structure
D. Linear form
Answer: C
Clarification: Protein folding is a process in which a polypeptide is folded into a 3-dimensional conformation which is necessary for proper protein function. Failure to fold can produce inactive protein. A protein molecule folds during or after its biosynthesis.

2. Chaperones are the molecular protein which assists in proper protein folding or prevents them from aggregating.
A. True
B. False
Answer: A
Clarification: Molecular chaperones are proteins which binds to incompletely folded protein to assist their proper folding. These proteins also assist the formation of oligomeric structures and for transport of proteins by membranes.

3. Which of them contains all the information required to fold the polypeptide chain in its 3-D structure?
A. DNA sequences
B. RNA
C. Histone protein
D. Amino acid sequences
Answer: D
Clarification: The native conformation of a protein is determined by its amino acid sequences. This hypothesis was proved by an experiment, in which denaturation followed by renaturation folds the chain in its native structure.

4. Which sentence is INCORRECT regarding molten globule state of protein?
A. Hydrophobic interaction among non-polar residues
B. The collapsed state
C. It is less compact
D. The denatured state
Answer: D
Clarification: Molten globule is a state in which interior side chains remain mobile, less compact and there is no proper packing. This state is completely different from the native and denatured state.

5. Which of the following name is given to molecular chaperones?
A. Allosteric protein
B. Heat shock protein
C. Denaturation protein
D. Ribonuclease
Answer: B
Clarification: The ability of chaperones to synthesis in large amount after a brief exposure to elevated temperature(42°C. makes them heat shock protein(Hsp). Basically, the eukaryotic cell has two major families of chaperones called Hsp60 and Hsp70.

6. Which of these heat shock proteins prevent protein misfolding and maintain polypeptide chain in the unfolded state.
A. Hsp60
B. Hsp28
C. Hsp70
D. Hsp32
Answer: C
Clarification: Hsp70 is induced by stress and these are the primary proteins which prevent polypeptide chain from misfolding and maintained it in an unfolded state. It also helps in translocation of the protein from the cytosol into ER or mitochondria.

7. Among all the heat shock proteins which one is known as chaperonins?
A. Hsp70
B. Hsp32
C. Hsp60
D. Hsp30
Answer: C
Clarification: Hsp60 family of chaperones forms a large barrel-shaped structure that acts later when protein is being fully synthesized. Chaperonins bind incorrectly folded, partly folded or unfolded protein but not in their native state.

8. Which one of the following reagent is also known a Sanger’s reagent?
A. 1-fluoro-2,4-dinitrobenzene (FDNB)
B. Phenylisothiocyanate
C. Cyanogen bromide
D. β-mercaptoethanol
Answer: A
Clarification: FDNB reacts with a free amino group of N-terminal amino acid in alkaline solution to form yellow dinitrophenol. This reaction was first used by Sanger to determine the primary structure of the polypeptide hormone.

9. Proteolytic enzyme trypsin cleaves protein at which of these specific sites?
A. Carboxyl side of Alanine, Glycine
B. Carboxyl side of Lysin or Arginine
C. Carboxyl side of aromatic amino acid
D. The amino side of aromatic amino acid
Answer: B
Clarification: The specificity of these enzymes determined by the side chain of amino acid on either side of a peptide bond. This cleavage is necessary to sequence protein which is made up of more than 50 amino acid residues.

10. Mark the correct statement which depicts the correct statement of protein assay?
A. To determine the amount of protein
B. To characterize the function of the protein
C. To determine the structure of the protein
D. To determine the sequence of the protein
Answer: A
Clarification: Protein assay is a technique to determine the amount of protein in an unknown solution. It is done by measuring the absorbance at 280nm. Aromatic side chain containing amino acids like tyrosine, tryptophan, and phenylalanine exhibit strong UV light absorbance.

11. In a living organism, strong interactions between molecules are formed by a certain type of bond. Name that?
A. Hydrogen bonding
B. Covalent bond
C. Electrostatic interactions
D. Van der Waals forces
Answer: B
Clarification: Covalent bond is considered as a strong bond between molecules whereas rest options are of the non-covalent bond which is regarded as weak interactions. In a covalent bond, electrons are shared by both the atoms which makes it stronger.

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250+ TOP MCQs on Lipid Metabolism and Answers Quiz Exam

This set of Life Sciences Multiple Choice Questions on “Lipid Metabolism”.

1. Name the most active organs in the animal body which have the ability to synthesize triacylglycerol?
A. Spleen
B. Kidney
C. Liver and intestines
D. Adipose tissues

Answer: C
Clarification: In general, all plants and animals have the ability to synthesize triacylglycerol (TAG). In animals, liver and intestines are two most active sites for TAG synthesis. Adipose tissues are the storage site for fat.

2. Triacylglycerol stored in the body as cytoplasmic lipid droplets.
A. True
B. False

Answer: A
Clarification: Triacylglycerol is stored as the cytoplasmic lipid droplets like fat globules, oil bodies, lipid particles, adiposomes etc. These triacylglycerols are enclosed by a monolayer of phospholipids and hydrophobic proteins.

3. Which of the following pathway is not used for triacylglycerol synthesis?
A. Glycerol 3-phosphate pathway
B. Glyoxylate pathway
C. Monoacylglycerol pathway
D. Kennedy pathway

Answer: B
Clarification: Except glyoxylate pathway, all three pathways have been used for the synthesis of triacylglycerol. Kennedy pathway and glycerol 3-phosphate pathway are same which predominates in the liver and adipose tissue while the monoacylglycerol pathway used in intestines.

4. Which of the following enzyme is not used in the synthesis of triacylglycerol?
A. Glycerol-3-phosphate acyltransferase
B. Acylglycerophophate acyltransferase
C. Phosphatidic acid phosphohydrolase
D. Glycogen phosphorylase

Answer: D
Clarification: Triacylglycerol biosynthetic pathway involves the formation of triacylglycerol by glycerol-3-phosphate. It involves four steps catalyzed by all the above enzymes except glycogen phosphorylase. The fourth enzyme is Diacylglycerol acyltransferase which converts diacylglycerol to triacylglycerol.

5. What is lipolysis?
A. Hydrolysis of triacylglycerol
B. Formation of lipids
C. Breakdown of ketone bodies
D. Formation of ketone bodies

Answer: A
Clarification: Hydrolysis of triacylglycerol by lipase is called lipolysis. Triacylglycerol stored in adipose tissues of animals in an insoluble form where they constantly synthesized and broken down again.

6. Which of the following hormone is not used in the hydrolysis of triacylglycerol into the fatty acids in adipose tissues?
A. Epinephrine
B. Norepinephrine
C. Glucagon
D. Insulin

Answer: D
Clarification: Triacylglycerols are converted to free fatty acids and glycerol under the influence of certain hormones. Hormones which control hydrolysis of the TAG are epinephrine, norepinephrine, and glucagon.

7. Mark the INCORRECT statement about the bile salt.
A. These are detergent substances
B. Stored in the gallbladder
C. It is hydrophobic in nature
D. It is made up of cholic acid

Answer: C
Clarification: The surface of bile salt molecule is both hydrophobic and hydrophilic in nature. Bile salts are made up of bile acids, synthesized in the liver and stored in the gallbladder. It facilitates the digestion of lipids.

8. Triacylglycerol packed with the apolipoprotein and cholesterol in lipoprotein aggregate is called_________
A. Chylomicrons
B. VLDL
C. HDL
D. LDL

Answer: A
Clarification: Triacylglycerol packed with cholesterol and apolipoprotein and forms chylomicron which moves through lymphatic system where lipoprotein lipase breaks it in fatty acids and glycerol. Finally, fatty acids absorbed as a fuel or stored.

9. What is the outcome of the accumulation of acetyl-CoA in the mitochondria of the liver?
A. It is used as an energy source
B. It has broken down in to free fatty acids
C. It gets converted to oxaloacetate
D. It forms ketone bodies

Answer: D
Clarification: Most of the acetyl-CoA has been used by citric acid cycle but during starvation acetyl-CoA accumulated in the mitochondria of liver and forms ketone bodies. Formation of ketone bodies by acetyl-CoA is known as ketogenesis.

10. Name the energy source of the brain during starvation?
A. Fat
B. Ketone bodies
C. Protein
D. Lipids

Answer: B
Clarification: In the absence of glucose or during prolonged starvation, the brain gets energy from ketone bodies by converting it to acetyl-CoA. This mechanism is absent in liver so, it cannot utilize ketone bodies as an energy source.

11. What is the biosynthetic source of all steroid hormones?
A. Cholesterol
B. Ketone bodies
C. Carbohydrate
D. Protein

Answer: A
Clarification: Pregnenolone is the precursor of all steroid hormones which is synthesized by cholesterol and catalyzed by desmolase enzyme. It involves the shortening of hydrocarbon chain of cholesterol and hydroxylation of steroid nucleus.

12. The cholesterol serves as the precursor for the following biosynthetic pathways, EXCEPT
a) Bile acid synthesis
b) Steroid hormone synthesis
c) Aldosterone synthesis
d) Thyroid hormone synthesis

13. Which of the following lipids act as lungs surfactants?
a) Phosphatidylcholine
b) Phosphatidylethanolamine
c) Ceramide
d) Phosphatidylinositol

14. Identify the simple lipid from the following?
a) Lecithin
b) Fatty acid
c) Triacylglycerol
d) Steroids

15. All of the following are complex lipids, Except?
a) Phosphatidic acid
b) Cerebroside
c) Cardiolipin
d) Cholesterol

16. Which of the following is an essential fatty acid?
a) Linolenic acid
b) Arachidonic acid
c) Oleic acid
d) Palmitic acid

17. Bile acid is derived from:
a) Cholesterol
b) Amino acids
c) Fatty acids
d) Bilirubin

18. Which of the following lipid is mostly present in mitochondrial membranes?
a) Lecithin
b) Cephalin
c) Cardiolipin
d) Ceramide

19. Insulin enhances the uptake of triacylglycerols in adipose tissues. Which of the following enzyme is activated that facilitates the uptake?
a) Hormone-sensitive lipase
b) Lipoprotein lipase
c) LCAT
d) Apo C-II

20. Familial hypercholesterolemia is a genetic disorder of cholesterol metabolism. The defect lies in the…………………………………………………………………
a) Transport of cholesterol from extrahepatic tissue to the liver
b) Impairment of cholesterol degradative pathway
c) Impairment of uptake of cholesterol by tissues
d) Impairment of HDL metabolism due to deficiency of Apo-A

21. Which of the following inhibits acetyl CoA carboxylase- a rate-limiting enzyme of fatty metabolism?
a) Citrate
b) ATP
c) Malonyl CoA
d) Acyl CoA

22. Acetyl CoA serves as the precursor for the synthesis of cholesterol, and the biosynthesis of cholesterol is tightly regulated.
Which of the following step is a regulatory step of cholesterol biosynthesis?
a) Formation 3-hydroxy-3-methylglutaryl COA
b) Formation of Mevalonate
c) Formation of Isoprenoid Unit
d) Formation of Lansterol

23. The enzyme that regulates the biosynthesis of cholesterol also serves as the druggable target for the reduction of hypercholesterolemia (increase blood cholesterol). Identify the regulatory enzyme from the following options:
a) HMG-CoA synthase
b) HMG- CoA reductase
c) Lansterol oxidase
d) Cholesterol synthase

24. Which of the following hormone increases the synthesis of cholesterol by regulating the enzyme HMG CoA reductase?
a) Insulin
b) Glucagon
c) Glucocorticoids
d) All of the above

25. Sterol Regulatory Binding Protein binds to DNA at the sterol regulatory element to increase the expression of HMG CoA reductase, and synthesis of cholesterol.
What happens when there is the presence of a high cellular concentration of cholesterol?
a) Increases the proteolytic cleavage, release, and shuttling of SREBP into the nucleus
b) Decreases the proteolytic cleavage and release of SREBP from ER
c) Activates SREBP by inducing the conformational change
d) Inhibit SREBP by competitively binding to DNA binding site of SREBP

26. Hormones such as insulin & glucagon regulate HMG CoA reductase by a phosphorylation and dephosphorylation process.
Phosphorylation of HMG CoA reductase results in decreased enzyme activity.
Identify the correct statement from the following:
a) Insulin inhibits kinase that phosphorylates HMG CoA reductase
c) Insulin activates kinase that phosphorylates HMG CoA reductase
c) Insulin activates the phosphatase that removes a phosphate group from HMG CoA reductase
d) Insulin inhibits kinase that phosphorylates HMG CoA reductase

27. Hypercholesterolemia refers to a condition with high cholesterol with a serum cholesterol level of………………………………………
a) >160 mg/dL
b) >200 mg/dL
c) >240 mg/dL
d) >280 mg/dL

28. Which of the following enzyme is responsible for the conversion of cholesterol to cholesterol ester inside the cells?
a) Lecithin Cholesterol Acyl Transferase
b) Acyl CoA Cholesterol Acyl Transferase
c) Cholesterol Esterase
d) None of the Above

29. Which of the following glycolytic intermediates serves as the precursor for the backbone for the synthesis of Triglycerides, Phosphatidylcholine, Phosphatidylethanolamine?
a) Glyceraldehyde-3-phosphate
b) Pyruvate
c) 1-3 Bisphosphoglycerate
d) 3-Phosphoglycerate

30. Ceramide is synthesized in the endoplasmic reticulum from the amino acid serine.
Ceramide is an important signaling molecule (second messenger) that regulates the pathways including which of the following process?
a) apoptosis
b) cell senescence
c) cell differentiation
d) All of the above

31. Identify the phospholipid that possesses a surfactant activity and is synthesized shortly before parturition in full-term infants, and its deficiency in the lungs can cause respiratory distress syndrome.
a) Dipalmitoylphosphatidyletholamine
b) Ceramide
c) Dipalmitoylphosphatidylcholine
d) All of the above

32. A child is was brought to the hospital with the clinical presentation of mental retardation, blindness, and muscular weakness. The biochemical examination showed the accumulation of GM2 gangliosides in the tissues.
What is the possible cause of the disease?
a) Tay Sachs Disease caused by Hexosaminidase A deficiency
b) Fabry Disease caused by Alpha-Galactosidase deficiency
c) Krabbe Disease caused by Beta-Galactosidase deficiency
d) Gaucher Disease caused by Beta-Glucosidase deficiency

250+ TOP MCQs on Bacterial Taxonomy and Answers

Life Sciences Multiple Choice Questions on “Bacterial Taxonomy”.

1. Mark the common feature between eukaryotes and prokaryotes.
A. Shape of DNA
B. Number of chromosomes
C. A prokaryotic cell is similar to a eukaryotic organelle
D. Cell wall
Answer: C
Clarification: In general, prokaryotes differs from the eukaryotic organism in every sense except its organelles i.e. mitochondria and chloroplast. It has to be believed that these organelles have been derived from bacteria as they share many common features (endosymbiotic theory).

2. Which of the following gene deduced the evolutionary relationship between the taxonomic groups?
A. 16S rRNA
B. 23S rRNA
C. 5S rRNA
D. 18S rRNA
Answer: A
Clarification: 16S ribosomal RNA acts as a signature sequence and is present in all the cells. These are approximately 1500bp in length. The organism of one taxonomic group has different conserved sequences than the other group.

3. Name the scientist who proposed the phylogenetic tree for living things.
A. Carlo Urbani
B. Louis Pasteur
C. Robert Koch
D. Carl Woese
Answer: D
Clarification: Carl Woese proposed the reorganization of five kingdoms into three kingdoms, based on the ribosomal RNA signature sequences. He placed protista, fungi, plants, and animals into a single group called eukaryotes.

4. The largest bacteria which can be visible by unaided eye is_______
A. Thiomargarita namibiensis
B. Lactobacillus
C. Mycoplasma
D. Pseudomonas
Answer: A
Clarification: Thiomargarita namibiensis and epulopiscium fishelsoni are the largest bacteria of 600 micrometers in length and 75 micrometers in diameter and are easily visible to eyes.

5. Which of the following is NOT the basic shape of the bacteria?
A. Rod shape
B. Square shape
C. Comma shape
D. Spiral shape
Answer: B
Clarification: There are four basic shapes of bacteria: rod shape is bacillus bacteria, comma shaped is vibrio bacteria, spiral shape is spirilla, and sphere shape of coccus.

6. What is sarcinae?
A. Cocci group of bacteria
B. Chainlike group of bacteria
C. Cubelike group of bacteria
D. Grapelike cluster of bacteria
Answer: C
Clarification: The division of bacteria into multiple groups form different structures like the chainlike division is called streptococci; the grapelike cluster is called staphylococci. Similarly, a group of eight bacteria into the cubelike structure is called sarcinae.

7. Which of the following bacteria is pleomorphic?
A. Mycobacteria
B. Streptococcus
C. Pseudomonas
D. Corynebacterium
Answer: D
Clarification: Pleomorphic bacteria lack a single characteristic shape. Most of the bacteria are of monomorphic while corynebacterium is pleomorphic and has many shapes.

8. Gram staining is specialized staining.
A. True
B. False
Answer: B
Clarification: Bacterial staining is of three types: simple, differential, and specialized. Gram staining is a differential staining procedure used to differentiate bacterial species into gram positive and gram negative.

9. Name the acid present in the cell wall of bacteria which helps in retaining its color during the acid-fast test?
A. Mycolic acid
B. Teichoic acid
C. Malic acid
D. Tartaric acid
Answer: A
Clarification: Mycolic acid is present in the cell wall of acid-fast bacteria which helps in retaining its color during the acid-fast test while non acid-fast bacteria decolorized after reacting with acid-alcohol.

10. Which of the following organisms have thick peptidoglycan in their cell wall?
A. Gram-negative bacteria
B. Gram-positive bacteria
C. Yeast
D. Molds
Answer: B
Clarification: Peptidoglycan is a specific feature of bacteria; it is present in the cell wall of bacteria and composed of NAG and NAM acid. Gram-negative bacteria have a thin peptidoglycan layer while gram-positive bacteria have a thick peptidoglycan layer.

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250+ TOP MCQs on Genetic Linkage and Answers

Life Sciences Multiple Choice Questions on “Genetic Linkage”.

1. The tendency of two or more than two genes to stay together during inheritance is called ___________
A. Genetics
B. Gene interaction
C. Crossing over
D. Linkage
Answer: D
Clarification: Linkage is the tendency of two or more than two genes to stay together during the inheritance. It exists in two forms i.e. cis and trans.

2. Which of the following statement is NOT true regarding linkage group?
A. Group of physically linked genes
B. Represent a haploid number of chromosomes
C. Shown by linkage map
D. Linkage groups are not correlated with each other
Answer: D
Clarification: The linkage group refers to the group of genes physically linked together. The number of linkage group represents the haploid number of chromosomes in a species, i.e. the number of linkage group can be correlated as the number of homologous pairs.

3. The linkage maps are constructed by using recombination frequencies between genes.
A. True
B. False
Answer: A
Clarification: The linkage map is the representation of all the genes of a linkage group on a single line in the same order in which they are present on the chromosome.

4. What is the unit of linkage map?
A. Morgan
B. Centi-morgan
C. Centimeter
D. Angstrom
Answer: B
Clarification: The linkage maps are constructed by using recombination frequencies between genes which is determined by the test cross. The distance is measured from centi-morgan (cM), it represents the unit of the map.

5. What is the maximum percentage of recombination frequency between two genes?
A. 75%
B. 100%
C. 50%
D. 25%
Answer: B
Clarification: Recombination frequency is the measure of genetic linkage; it should not exceed 50%. The maximum limit of recombination is 50%.

6. Name the phenomenon which can break the occurrence of linkage?
A. Crossing over
B. Linkage
C. Reconstruction
D. Breakage
Answer: A
Clarification: Linkage can be broken by the process of homologous recombination (crossing over) which occurs at the pachytene stage of prophase I.

7. Failure in which of the following phenomenon would result in linkage?
A. Law of dominance
B. Law of segregation
C. Law of independent assortment
D. Law of separation
Answer: C
Clarification: Alignment of chromosomes in metaphase one will give two gametes, but a failure of independent assortment would result in the linkage of genes on the chromosomes.

8. Name the organism whose first genetic map was made?
A. Rat
B. Arabidopsis
C. Fly
D. Drosophila
Answer: D
Clarification: T.H. Morgan first studied linkage in Drosophila malanogester in which genes on a chromosome are linked (systemic gene).

9. Two genes are 70cM apart, calculate the recombination frequency?
A. 50%
B. 100%
C. 25%
D. 23%
Answer: A
Clarification: Recombination frequency is the measure of genetic linkage. Recombination frequency should not exceed 50%. The maximum limit of recombination is 50%.

10. Name the sites of DNA, which have a high probability of crossing over?
A. Cold spots
B. Hot spots
C. Covalent bond
D. Hydrophobic bond
Answer: B
Clarification: There are certain sites on DNA, which have a high probability of crossing over called hot spots and those sites which have a low probability of crossing over are called cold spots.

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250+ TOP MCQs on Nucleic Acids and Answers

Life Sciences Multiple Choice Questions on “Nucleic Acids”.

1. The monomeric unit of nucleic acid are called ___________
A. Nucleotides
B. Nucleosides
C. Pyrimidines
D. Purines
Answer: A
Clarification: Nucleotides are the monomeric unit of nucleic acid; therefore, these are considered as polynucleotides. It is made up of three components i.e. nitrogenous base, sugar, and an ion of phosphoric acid. Nucleotides are phosphate easters of the nucleoside.

2. Who discovered nucleic acid?
A. Watson and Crick
B. Griffith
C. Friedrich Miescher
D. Walter Gilbert
Answer: C
Clarification: Friedrich Miescher first discovered nucleic acid from nuclei of pus cells from discarded bandages and called it nuclein. It was later revealed as a mixture of basic protein and phosphorus-containing acid, now called nucleic acid.

3. Name the pyrimidine base which is found in RNA but not in DNA?
A. Thymine
B. Uracil
C. Adenine
D. Guanine
Answer: B
Clarification: Uracil is considered like thymine, but it lacks methyl group at the C5 position. Uracil is a component of RNA whereas it is not found in DNA.

4. Name those purine bases which are commonly found in DNA and RNA?
A. Adenine and guanine
B. Cytosine and thymine
C. Adenine and thymine
D. Cytosine and guanine
Answer: A
Clarification: There are two types of nitrogenous bases in both RNA and DNA, purines and pyrimidines. Adenine and guanine are purines while cytosine and thymine come under pyrimidines.

5. Deoxyribose sugar is found in DNA.
A. True
B. False
Answer: A
Clarification: Ribose sugar is found in RNA, if the hydroxyl group(OH) at the 2nd position of ribose sugar is replaced by hydrogen (H) it will convert to deoxyribose which is DNA’s sugar.

6. Which of these statements are TRUE for a glycosidic bond?
A. The bond between sugar and the nitrogenous base
B. The bond between the two sugar residues
C. The bond between sugar and phosphate
D. The bond between base and phosphate
Answer: A
Clarification: The glycosidic bond formed between sugar and nitrogenous base during the formation of a nucleoside. This bond is held to be in β-configuration with respect to the ribose sugar leaving it’s base free to rotate around the bond.

7. What is the energy currency of the living cell?
A. GTP
B. NADH
C. FADH
D. ATP
Answer: D
Clarification: ATP is the energy currency of the cell as it acts as a donor of high energy phosphate. It also acts as a chemical link between catabolism and anabolism. In its active form ATP is complexed with Mg2+ or Mn2+.

8. The primary structure of DNA and RNA proceeds in which direction?
A. 3’ —–> 5҆’
B. 5’ —–> 3’
C. 4’ —–> 6’
D. 3’ —–> 6’
Answer: B
Clarification: The primary structure is described by the order in which bases occur in a polypeptide. The convention is to arrange them from left to right from 5’ end to 3’ end. 5’ end of the polypeptide is attached to phosphate while 3’ end is usually a free hydroxyl group.

9. Which bond is used to stabilize the double helix of DNA?
A. Hydrophobic bond
B. Hydrogen bond
C. Covalent bond
D. Ionic bond
Answer: B
Clarification: Polynucleotide runs on the backbone of the phosphate-sugar chain. The base pairing of these nucleotide gives secondary structure. The secondary structure of DNA is its double helix which held together by hydrogen bonding between the bases.

10. Which of these statements are INCORRECT according to chargaff’s rules?
A. The molar ratio of A to T or C to G = 1
B. The sum of purine = sum of pyrimidine
C. The % C+G ≠ % A+T
D. The composition of DNA remains the same in all the species
Answer: D
Clarification: Erwin Chargaff proposed two rules which played a significant role in the discovery of the double helix structure of DNA. According to its second rule, the composition of DNA varies from one species to other. Statement composition of DNA remains the same in all the species is incorrect.

11. A purified DNA sample of leaf contains 20.0 mole of guanine. Calculate the approximate percentage of purine residues?
A. 30%
B. 40%
C. 60%
D. 20%
Answer: A
Clarification: According to chargaff’s rules, C=G= 20%; A=T
(A+G) + (T+C. =100%
(A+20) + (T+20) =100%
(A+20) + (A+20) = 100%
2A= 100-40%
A = 30%.

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