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#	Question	Answer
1	What are the two types of nucleic acids found in living systems?	DNA and RNA.
2	What are nucleic acids polymers of?	Nucleotides.
3	Which sugar is present in RNA?	Ribose.
4	Which base is present in DNA but absent in RNA?	Thymine.
5	What linkage joins two nucleotides in a polynucleotide chain?	3'–5' phosphodiester linkage.
6	What is present at the 5' end of a polynucleotide chain?	A free phosphate moiety attached to the 5' carbon of sugar.
7	What is another chemical name for thymine?	5-methyl uracil.
8	In which year was the Double Helix model proposed?	1953.
9	What acts as a template during DNA replication?	Each parental DNA strand.
10	What does anti-parallel polarity mean in DNA?	One strand runs 5'→3' while the other runs 3'→5'.
11	What is the pitch of the DNA helix?	3.4 nm.
12	What does the Central Dogma state?	Genetic information flows from DNA → RNA → Protein.
13	What is the length of *E. coli* DNA mentioned in the text?	1.36 mm.
14	What type of proteins are histones?	Positively charged basic proteins.
15	Approximately how many base pairs are present in a nucleosome?	About 200 bp.
16	What is euchromatin?	Loosely packed chromatin that stains lightly.
17	Which bacterium did Frederick Griffith use in his experiments?	*Streptococcus pneumoniae*.
18	Which strain of *Streptococcus pneumoniae* is virulent?	S strain.
19	What characteristic did transformed R strain bacteria acquire?	Ability to synthesise a smooth polysaccharide coat.
20	Which enzymes did not affect bacterial transformation?	Proteases and RNases.
21	Which organisms were used by Hershey and Chase in their experiment?	Bacteriophages and bacteria.
22	Why did Hershey and Chase use radioactive sulfur in another set of viruses?	Because proteins contain sulfur.
23	How were viral coats removed from bacteria in Hershey-Chase experiment?	By agitation in a blender.
24	What did Hershey and Chase conclude from their experiment?	DNA is the genetic material transferred from virus to bacteria.
25	What are the essential criteria for a molecule to act as genetic material?	Replication, stability, mutation capability, and expression in the form of Mendelian characters.
26	Why is RNA chemically less stable than DNA?	Due to the reactive 2'-OH group present in RNA nucleotides.
27	Which nucleic acid mutates at a faster rate?	RNA.
28	Around which molecule has the protein synthesising machinery evolved?	RNA.
29	Besides acting as genetic material, what additional role did RNA perform?	Catalyst.
30	What did Watson and Crick suggest about DNA strands during replication?	The two strands separate and act as templates for new strands.
31	What type of DNA appears after one generation in semiconservative replication?	Hybrid DNA.
32	Why is the enzyme called DNA-dependent DNA polymerase?	Because it uses DNA as a template to synthesise DNA.
33	Why must DNA replication be highly accurate?	Errors during replication cause mutations.
34	What is the small opening in DNA during replication called?	Replication fork.
35	Why can DNA replication not occur along the entire length of DNA at once?	Because separating the entire DNA strands requires very high energy.
36	Which enzyme joins discontinuously synthesised DNA fragments?	DNA ligase.
37	During which phase of the eukaryotic cell cycle does DNA replication occur?	S-phase.
38	Does transcription copy the entire DNA molecule?	No, only a segment of DNA is copied.
39	Which DNA strand acts as template during transcription?	The strand with polarity 3' → 5'.
40	In which direction is the promoter located relative to the structural gene?	Towards the 5' end (upstream).
41	What are regulatory sequences?	Additional DNA sequences present upstream or downstream to the promoter.
42	What are exons?	Coding or expressed sequences that appear in mature or processed RNA.
43	Name the three major types of RNA in bacteria.	mRNA, tRNA, and rRNA.
44	What does bacterial RNA polymerase transcribe?	All types of RNA.
45	Which phase of transcription is catalysed directly by RNA polymerase?	Elongation.
46	Which rRNAs are transcribed by RNA polymerase I?	28S, 18S, and 5.8S rRNA.
47	What is splicing?	Removal of introns and joining of exons.
48	What does the presence of introns suggest about genomes?	It reflects antiquity and dominance of the RNA world.
49	Which scientist developed the chemical method for synthesising RNA molecules with defined sequences?	Har Gobind Khorana.
50	How many codons code for amino acids?	61 codons.
51	What is meant by universal genetic code?	The same codon specifies the same amino acid in most organisms.
52	What is a point mutation?	Change in a single base pair in DNA.
53	What happens if three or multiples of three bases are inserted or deleted?	One or more amino acids are added or removed without changing the reading frame.
54	What is present in the anticodon loop of tRNA?	Bases complementary to the codon.
55	What is the secondary structure of tRNA commonly compared to?	Clover-leaf structure.
56	What are insertion or deletion mutations causing reading frame changes called?	Frameshift mutations.
57	Which part of tRNA binds amino acids?	Amino acid acceptor end.
58	What is amino acid activation before translation called?	Charging of tRNA or aminoacylation of tRNA.
59	What initiates translation on ribosomes?	Binding of the small ribosomal subunit to mRNA.
60	Which codon acts as the start codon in translation?	AUG.
61	During elongation, how do aminoacyl tRNAs bind to mRNA?	By complementary base pairing between codon and anticodon.
62	What is regulation of gene expression?	Control of formation of a polypeptide at different levels.
63	Which level regulates protein synthesis directly?	Translational level.
64	What regulates gene expression in simple terms?	Metabolic, physiological, or environmental conditions.
65	What are regulatory proteins that decrease transcription called?	Repressors.
66	Which scientists elucidated the lac operon?	Francois Jacob and Jacques Monod.
67	How many structural genes are present in lac operon?	Three.
68	What is the function of permease?	Increases permeability of the cell to β-galactosides.
69	What happens to lactose in the presence of permease?	It is transported into the bacterial cell.
70	What happens when the repressor binds to the operator?	It prevents RNA polymerase from transcribing the operon.
71	Can glucose act as an inducer for lac operon?	No.
72	What determines the genetic information of an organism?	Sequence of bases in DNA.
73	What was the estimated sequencing cost per base pair at the beginning of HGP?	US $3 per bp.
74	What was one major goal of HGP regarding genes?	Identification of approximately 20,000–25,000 genes.
75	What does ELSI stand for in Human Genome Project?	Ethical, Legal, and Social Issues.
76	Name some non-human organisms whose genomes were sequenced.	Bacteria, yeast, *Caenorhabditis elegans*, *Drosophila*, rice, and *Arabidopsis*.
77	Into what sizes is genomic DNA converted for sequencing?	Random fragments of relatively smaller sizes.
78	Which scientist also developed methods for amino acid sequencing in proteins?	Frederick Sanger.
79	Which human chromosome was sequenced last?	Chromosome 1.
80	What are microsatellites?	Repetitive DNA sequences used in genetic mapping.
81	Approximately how many genes are estimated in the human genome?	About 30,000 genes.
82	What are repetitive sequences?	DNA sequences repeated many times.
83	Approximately how many genes are present on the Y chromosome?	231 genes.
84	What percentage of DNA base sequence is identical among humans?	99.9%.
85	How are repetitive DNA sequences separated from bulk genomic DNA?	By density gradient centrifugation.
86	Do repetitive DNA sequences code for proteins?	No.
87	What is DNA polymorphism?	Variation at the genetic level due to mutations.
88	Why do mutations accumulate more in non-coding DNA?	Because they usually do not affect reproductive ability.
89	Which technique was initially used in DNA fingerprinting?	Southern blot hybridisation.
90	To which membranes are DNA fragments transferred during blotting?	Nitrocellulose or nylon membranes.
91	Why does VNTR vary among individuals?	Because copy number of repeats differs among chromosomes and individuals.
92	Which technique increased the sensitivity of DNA fingerprinting?	Polymerase Chain Reaction (PCR).
93	Which nucleic acid is chemically and structurally more stable?	DNA.
94	Why are the two DNA strands complementary?	Due to specific base pairing.
95	What interrupts coding sequences in eukaryotic genes?	Introns.
96	What role does tRNA play in translation?	Adapter molecule between codons and amino acids.
97	Why must transcription and translation be tightly regulated?	Because they are energetically expensive processes.
98	What regulates the lac operon?	Amount of lactose in the medium.
99	Group the following as nitrogenous bases and nucleosides: Adenine, Cytidine, Thymine, Guanosine, Uracil, Cytosine.	* Nitrogenous bases: Adenine, Thymine, Uracil, Cytosine, * Nucleosides: Cytidine, Guanosine
100	Which property of DNA double helix suggested semiconservative replication?	Complementary base pairing between strands.
101	How did Hershey and Chase distinguish DNA from protein?	Using radioactive phosphorus for DNA and radioactive sulfur for proteins.
102	What is the template strand in transcription?	DNA strand with polarity 3'→5' used for RNA synthesis.
103	What is transcription?	Copying of genetic information from DNA into RNA.