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#	Question	Answer
1	What is the genetic material in the majority of organisms?	DNA (Deoxyribonucleic acid).
2	What are the two types of nucleic acids found in living systems?	DNA and RNA.
3	Which nucleic acid acts as genetic material in most organisms?	DNA.
4	In some viruses, which molecule acts as genetic material?	RNA.
5	What is the primary role of RNA in most organisms?	It functions mainly as a messenger.
6	Name additional roles of RNA besides acting as a messenger.	Adapter, structural, and catalytic roles.
7	What are nucleic acids polymers of?	Nucleotides.
8	What is DNA chemically described as?	A long polymer of deoxyribonucleotides.
9	DNA length is usually measured in terms of what?	Number of nucleotides or base pairs (bp).
10	How many base pairs are present in bacteriophage lambda?	48502 bp.
11	What are the three components of a nucleotide?	Nitrogenous base, pentose sugar, and phosphate group.
12	Which sugar is present in RNA?	Ribose.
13	Which sugar is present in DNA?	Deoxyribose.
14	Name the purine bases.	Adenine and Guanine.
15	Name the pyrimidine bases.	Cytosine, Uracil, and Thymine.
16	Which nitrogenous base is common to both DNA and RNA?	Cytosine.
17	Which base is present in DNA but absent in RNA?	Thymine.
18	Which base replaces thymine in RNA?	Uracil.
19	What linkage joins a nitrogenous base to pentose sugar?	N-glycosidic linkage.
20	What is formed when a nitrogenous base combines with sugar?	Nucleoside.
21	What is formed when phosphate attaches to a nucleoside?	Nucleotide.
22	What linkage joins two nucleotides in a polynucleotide chain?	3'–5' phosphodiester linkage.
23	What forms the backbone of a polynucleotide chain?	Sugar and phosphate.
24	What projects from the backbone of a polynucleotide chain?	Nitrogenous bases.
25	Which end of a polynucleotide chain has a free phosphate group?	5' end.
26	Which end of a polynucleotide chain has a free OH group?	3' end.
27	What is present at the 5' end of a polynucleotide chain?	A free phosphate moiety attached to the 5' carbon of sugar.
28	What is present at the 3' end of a polynucleotide chain?	A free OH group attached to the 3' carbon of sugar.
29	What forms the backbone of a polynucleotide chain?	Sugar and phosphate.
30	In RNA, which additional group is present at the 2' position of ribose sugar?	An additional –OH group.
31	Which nitrogenous base is present in RNA in place of thymine?	Uracil.
32	What is another chemical name for thymine?	5-methyl uracil.
33	Who first identified DNA as an acidic substance in the nucleus?	Friedrich Meischer.
34	In which year was DNA first identified by Friedrich Meischer?	1869.
35	What name did Friedrich Meischer give to DNA?	Nuclein.
36	Who proposed the Double Helix model of DNA?	James Watson and Francis Crick.
37	In which year was the Double Helix model proposed?	1953.
38	On whose X-ray diffraction data was the DNA model based?	Maurice Wilkins and Rosalind Franklin.
39	Which scientist observed that the ratio of Adenine to Thymine and Guanine to Cytosine is constant in double-stranded DNA?	Erwin Chargaff.
40	What property do the two DNA strands show because of base pairing?	Complementarity.
41	Why can the sequence of one DNA strand predict the sequence of the other strand?	Because the two strands are complementary.
42	What acts as a template during DNA replication?	Each parental DNA strand.
43	What are the daughter DNA molecules formed after replication?	DNA molecules identical to the parental DNA.
44	How many polynucleotide chains are present in DNA?	Two.
45	What constitutes the backbone of DNA?	Sugar-phosphate backbone.
46	In which direction do the two DNA strands run?	Anti-parallel direction.
47	What does anti-parallel polarity mean in DNA?	One strand runs 5'→3' while the other runs 3'→5'.
48	Which bases are connected by two hydrogen bonds?	Adenine and Thymine.
49	Which bases are connected by three hydrogen bonds?	Guanine and Cytosine.
50	Why is the distance between the two DNA strands almost uniform?	Because a purine always pairs with a pyrimidine.
51	In which fashion are the two DNA strands coiled?	Right-handed fashion.
52	What is the pitch of the DNA helix?	3.4 nm.
53	Approximately how many base pairs are present in one turn of DNA helix?	10 base pairs.
54	What is the distance between two consecutive base pairs in DNA?	Approximately 0.34 nm.
55	What provides additional stability to the DNA double helix besides hydrogen bonds?	Stacking of one base pair over another.
56	Who proposed the Central Dogma of molecular biology?	Francis Crick.
57	What does the Central Dogma state?	Genetic information flows from DNA → RNA → Protein.
58	In some viruses, genetic information flows from which molecule to DNA?	RNA to DNA.
59	In some viruses, in which direction does genetic information flow?	From RNA to DNA.
60	What is the approximate length of DNA double helix in a typical mammalian cell?	Approximately 2.2 metres.
61	Why is DNA packaging necessary in cells?	Because DNA length is far greater than the size of the nucleus.
62	What is the length of *E. coli* DNA mentioned in the text?	1.36 mm.
63	In prokaryotes like *E. coli*, where is DNA located?	In a region called nucleoid.
64	Why is DNA held with proteins in the nucleoid?	Because DNA is negatively charged and proteins have positive charges.
65	How is DNA organised in the nucleoid?	In large loops held by proteins.
66	Which proteins are responsible for DNA organisation in eukaryotes?	Histones.
67	What type of proteins are histones?	Positively charged basic proteins.
68	Which amino acids are abundant in histones?	Lysine and arginine.
69	Why are histones positively charged?	Due to positively charged side chains of lysine and arginine.
70	What is a histone octamer?	A unit formed by eight histone molecules.
71	What structure is formed when DNA wraps around histone octamer?	Nucleosome.
72	Approximately how many base pairs are present in a nucleosome?	About 200 bp.
73	What is chromatin?	Thread-like stained bodies seen in the nucleus.
74	What are nucleosomes called when viewed under electron microscope?	Beads-on-string structure.
75	What happens to the beads-on-string structure during chromosome formation?	It gets packaged into chromatin fibres and further condensed into chromosomes.
76	Which proteins are required for higher level chromatin packaging?	Non-histone chromosomal (NHC) proteins.
77	What is euchromatin?	Loosely packed chromatin that stains lightly.
78	What is heterochromatin?	Densely packed chromatin that stains dark.
79	Which chromatin is transcriptionally active?	Euchromatin.
80	Which chromatin is transcriptionally inactive?	Heterochromatin.
81	What was the major unanswered question before 1926 regarding inheritance?	Which molecule acts as the genetic material.
82	Which bacterium did Frederick Griffith use in his experiments?	*Streptococcus pneumoniae*.
83	Which disease is caused by *Streptococcus pneumoniae*?	Pneumonia.
84	What are the two colony types produced by *Streptococcus pneumoniae*?	Smooth (S) colonies and Rough (R) colonies.
85	Why do S strain bacteria appear smooth?	Because they possess a mucous polysaccharide coat.
86	Why do R strain bacteria appear rough?	Because they lack the polysaccharide coat.
87	Which strain of *Streptococcus pneumoniae* is virulent?	S strain.
88	What happens when mice are infected with S strain bacteria?	They die from pneumonia infection.
89	What happens when mice are infected with R strain bacteria?	They do not develop pneumonia.
90	What happened when heat-killed S strain bacteria were injected into mice?	The mice survived.
91	What happened when live R strain and heat-killed S strain were injected together into mice?	The mice died.
92	What characteristic did transformed R strain bacteria acquire?	Ability to synthesise a smooth polysaccharide coat.
93	Did Griffith identify the biochemical nature of the genetic material?	No.
94	Which scientists worked to determine the biochemical nature of the transforming principle?	Oswald Avery, Colin MacLeod, and Maclyn McCarty.
95	What did Avery, MacLeod, and McCarty purify from heat-killed S cells?	Proteins, DNA, RNA, and other biochemicals.
96	Which molecule transformed live R cells into S cells?	DNA.
97	Which enzymes did not affect bacterial transformation?	Proteases and RNases.
98	What does protease digest?	Proteins.
99	What does RNase digest?	RNA.
100	What conclusion was drawn when DNase inhibited transformation?	DNA is the hereditary material.
101	Which scientists provided unequivocal proof that DNA is the genetic material?	Alfred Hershey and Martha Chase.
102	Which organisms were used by Hershey and Chase in their experiment?	Bacteriophages and bacteria.
103	What are bacteriophages?	Viruses that infect bacteria.
104	What happens when a bacteriophage infects a bacterium?	Its genetic material enters the bacterial cell.
105	What does the bacterial cell do with viral genetic material?	Treats it as its own and manufactures more virus particles.
106	Why did Hershey and Chase use radioactive phosphorus in one set of viruses?	Because DNA contains phosphorus.
107	Why did Hershey and Chase use radioactive sulfur in another set of viruses?	Because proteins contain sulfur.
108	Which component became radioactive when viruses were grown with radioactive phosphorus?	DNA.
109	Which component became radioactive when viruses were grown with radioactive sulfur?	Protein.
110	Why is DNA not labelled by radioactive sulfur?	Because DNA does not contain sulfur.
111	Why are proteins not labelled by radioactive phosphorus in Hershey-Chase experiment?	Because proteins do not contain phosphorus.
112	How were viral coats removed from bacteria in Hershey-Chase experiment?	By agitation in a blender.
113	How were virus particles separated from bacteria after blending?	By centrifugation.
114	What was observed in bacteria infected with viruses having radioactive DNA?	The bacteria became radioactive.
115	What did radioactive bacteria indicate in Hershey-Chase experiment?	DNA entered the bacterial cells.
116	What was observed in bacteria infected with viruses having radioactive proteins?	The bacteria were not radioactive.
117	What did Hershey and Chase conclude from their experiment?	DNA is the genetic material transferred from virus to bacteria.
118	Which experiment finally resolved the debate between protein and DNA as genetic material?	Hershey-Chase experiment.
119	Name two viruses in which RNA acts as genetic material.	Tobacco Mosaic Virus and QB bacteriophage.
120	Which nucleic acid is the predominant genetic material in organisms?	DNA.
121	Which nucleic acid mainly performs dynamic functions like messenger and adapter roles?	RNA.
122	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.
123	What is replication in terms of genetic material?	Ability to generate its replica.
124	Why can both DNA and RNA direct their duplication?	Due to base pairing and complementarity.
125	Why do proteins fail to act as genetic material?	They cannot direct their own duplication.
126	Why should genetic material be chemically and structurally stable?	So it does not change during life cycle, age, or physiological changes.
127	Why is RNA chemically less stable than DNA?	Due to the reactive 2'-OH group present in RNA nucleotides.
128	Why is RNA considered more reactive?	Because RNA can act as a catalyst.
129	Which nucleic acid is chemically less reactive and more stable?	DNA.
130	Why is DNA considered a better genetic material than RNA?	DNA is chemically less reactive and structurally more stable.
131	Which nitrogenous base provides additional stability to DNA?	Thymine.
132	Which nucleic acid mutates at a faster rate?	RNA.
133	Why do RNA viruses evolve faster?	Because RNA is unstable and mutates rapidly.
134	Which molecule can directly code for protein synthesis?	RNA.
135	Why is RNA efficient in expressing characters?	It directly codes for protein synthesis.
136	Why is DNA dependent on RNA?	DNA requires RNA for protein synthesis.
137	Around which molecule has the protein synthesising machinery evolved?	RNA.
138	Which molecule is preferred for storage of genetic information?	DNA.
139	Which molecule is better for transmission of genetic information?	RNA.
140	Which molecule is considered the first genetic material?	RNA.
141	Which essential life processes evolved around RNA?	Metabolism, translation, and splicing.
142	Besides acting as genetic material, what additional role did RNA perform?	Catalyst.
143	Why did DNA evolve from RNA?	DNA is more stable due to chemical modifications.
144	How does double-stranded nature of DNA increase stability?	Complementary strands resist changes through repair mechanisms.
145	Who proposed the semiconservative model of DNA replication?	Watson and Crick.
146	What is semiconservative DNA replication?	Each daughter DNA contains one parental and one newly synthesised strand.
147	What did Watson and Crick suggest about DNA strands during replication?	The two strands separate and act as templates for new strands.
148	Who experimentally proved semiconservative DNA replication?	Matthew Meselson and Franklin Stahl.
149	Which organism was used by Meselson and Stahl in their experiment?	*Escherichia coli*.
150	Which technique was used to distinguish heavy DNA from normal DNA?	Centrifugation in cesium chloride (CsCl) density gradient.
151	How long does *E. coli* take to divide?	20 minutes.
152	What type of DNA appears after one generation in semiconservative replication?	Hybrid DNA.
153	Which plant was used by Taylor and colleagues to prove semiconservative replication in chromosomes?	*Vicia faba* (faba bean).
154	Which radioactive compound was used by Taylor and colleagues?	Radioactive thymidine.
155	What did Taylor and colleagues prove?	DNA in chromosomes replicates semiconservatively.
156	Which enzyme is the main enzyme involved in DNA replication?	DNA-dependent DNA polymerase.
157	Why is the enzyme called DNA-dependent DNA polymerase?	Because it uses DNA as a template to synthesise DNA.
158	What does DNA polymerase catalyse?	Polymerisation of deoxynucleotides.
159	Why are DNA polymerases considered highly efficient enzymes?	They polymerise a large number of nucleotides in a short time.
160	How long does *E. coli* take to complete DNA replication?	About 18 minutes.
161	What is the approximate rate of DNA polymerisation in *E. coli*?	Approximately 2000 bp per second.
162	Why must DNA replication be highly accurate?	Errors during replication cause mutations.
163	Why is DNA replication energetically expensive?	Large numbers of nucleotides are polymerised using energy-rich substrates.
164	Which molecules act as substrates and energy sources during replication?	Deoxyribonucleoside triphosphates.
165	Which phosphates in deoxyribonucleoside triphosphates are high-energy phosphates?	The two terminal phosphates.
166	Besides DNA polymerase, what else is required for DNA replication?	Additional enzymes for high accuracy.
167	What is the small opening in DNA during replication called?	Replication fork.
168	In which direction does DNA polymerase synthesise DNA?	5' → 3' direction.
169	On which template strand is DNA replication continuous?	On the 3' → 5' template strand.
170	On which template strand is DNA replication discontinuous?	On the 5' → 3' template strand.
171	Which enzyme joins discontinuously synthesised DNA fragments?	DNA ligase.
172	Why can DNA replication not occur along the entire length of DNA at once?	Because separating the entire DNA strands requires very high energy.
173	What is the site where DNA replication occurs called?	Replication fork.
174	In which direction does DNA polymerase catalyse polymerisation?	5' → 3' direction.
175	Which strand undergoes continuous replication?	The strand with template polarity 3' → 5'.
176	Which strand undergoes discontinuous replication?	The strand with template polarity 5' → 3'.
177	Which enzyme joins discontinuously synthesised DNA fragments?	DNA ligase.
178	Can DNA polymerase initiate DNA replication on its own?	No.
179	Does DNA replication begin randomly in DNA?	No.
180	What is the specific region where DNA replication starts called?	Origin of replication.
181	Why are vectors required in recombinant DNA procedures?	Because they provide the origin of replication.
182	During which phase of the eukaryotic cell cycle does DNA replication occur?	S-phase.
183	What results if cell division fails after DNA replication?	Polyploidy.
184	What is transcription?	The process of copying genetic information from DNA into RNA.
185	Which principle governs transcription?	Complementarity.
186	During transcription, adenine pairs with which base in RNA?	Uracil.
187	Does transcription copy the entire DNA molecule?	No, only a segment of DNA is copied.
188	How many DNA strands are transcribed into RNA?	Only one strand.
189	Why are both DNA strands not transcribed simultaneously?	Because they would produce different RNAs and complementary double-stranded RNA.
190	What would happen if both RNA molecules formed during transcription were complementary?	They would form double-stranded RNA and prevent translation.
191	What are the three regions of a transcription unit?	Promoter, structural gene, and terminator.
192	Which DNA strand acts as template during transcription?	The strand with polarity 3' → 5'.
193	What is another name for the transcribed DNA strand?	Template strand.
194	Which strand has the same sequence as RNA except thymine in place of uracil?	Coding strand.
195	Which strand is displaced during transcription?	Coding strand.
196	Why is the coding strand called so?	Because its sequence resembles the RNA sequence.
197	In which direction is the promoter located relative to the structural gene?	Towards the 5' end (upstream).
198	What is the function of the promoter?	It provides the binding site for RNA polymerase.
199	What determines the template and coding strands in transcription?	The promoter.
200	What is the function of the terminator?	It defines the end of transcription.
201	What are regulatory sequences?	Additional DNA sequences present upstream or downstream to the promoter.
202	What is a gene defined as?	The functional unit of inheritance.
203	What is a cistron?	A segment of DNA coding for a polypeptide.
204	What type of structural genes are mostly found in eukaryotes?	Monocistronic genes.
205	What type of structural genes are mostly found in prokaryotes?	Polycistronic genes.
206	What are exons?	Coding or expressed sequences that appear in mature or processed RNA.
207	What are introns?	Intervening non-coding sequences that do not appear in mature RNA.
208	Why is the definition of a gene complicated in eukaryotes?	Due to split-gene arrangement with exons and introns.
209	Besides structural genes, what else affects inheritance of characters?	Promoter and regulatory sequences.
210	What are regulatory genes?	Regulatory sequences loosely defined as genes though they do not code for RNA or protein.
211	Name the three major types of RNA in bacteria.	mRNA, tRNA, and rRNA.
212	What is the function of mRNA?	It provides the template for protein synthesis.
213	What is the function of tRNA?	It brings amino acids and reads the genetic code.
214	What is the role of rRNA?	Structural and catalytic role during translation.
215	How many DNA-dependent RNA polymerases are present in bacteria?	One.
216	What does bacterial RNA polymerase transcribe?	All types of RNA.
217	To which site does RNA polymerase bind to initiate transcription?	Promoter.
218	Which substrates are used during transcription?	Nucleoside triphosphates.
219	Which principle governs RNA synthesis during transcription?	Complementarity.
220	What happens when RNA polymerase reaches the terminator region?	Nascent RNA and RNA polymerase fall off, ending transcription.
221	Which phase of transcription is catalysed directly by RNA polymerase?	Elongation.
222	Why can transcription and translation occur simultaneously in bacteria?	Because there is no separation between nucleus and cytoplasm and mRNA requires no processing.
223	What is meant by coupled transcription and translation?	Translation begins before transcription is fully completed.
224	How many RNA polymerases are present in eukaryotic nuclei?	At least three.
225	Which RNA polymerase transcribes rRNA in eukaryotes?	RNA polymerase I.
226	Which rRNAs are transcribed by RNA polymerase I?	28S, 18S, and 5.8S rRNA.
227	Which RNA polymerase transcribes tRNA and 5S rRNA?	RNA polymerase III.
228	Which RNA polymerase synthesises hnRNA?	RNA polymerase II.
229	What is hnRNA?	Heterogeneous nuclear RNA, the precursor of mRNA.
230	Why are primary transcripts in eukaryotes non-functional?	Because they contain both exons and introns.
231	What is splicing?	Removal of introns and joining of exons.
232	What is added to the 5' end during capping?	Methyl guanosine triphosphate.
233	What is added to the 3' end during tailing?	Adenylate residues (200–300).
234	What is the fully processed hnRNA called?	mRNA.
235	Where is processed mRNA transported after processing?	Out of the nucleus for translation.
236	What does the presence of introns suggest about genomes?	It reflects antiquity and dominance of the RNA world.
237	What is the process of translation?	Transfer of genetic information from nucleotides to amino acid sequence in proteins.
238	Who proposed that the genetic code should be made up of three nucleotides?	George Gamow.
239	Why did George Gamow propose a triplet genetic code?	Because four bases had to code for twenty amino acids.
240	How many codons are possible with a triplet code?	64 codons.
241	Which scientist developed the chemical method for synthesising RNA molecules with defined sequences?	Har Gobind Khorana.
242	Which scientist developed the cell-free system for protein synthesis?	Marshall Nirenberg.
243	Which enzyme developed by Severo Ochoa helped in RNA polymerisation?	Polynucleotide phosphorylase.
244	What type of RNA synthesis does polynucleotide phosphorylase perform?	Template-independent RNA synthesis.
245	What is the nature of the genetic code?	Triplet.
246	How many codons code for amino acids?	61 codons.
247	How many codons act as stop codons?	3 codons.
248	What are codons that do not code for amino acids called?	Stop codons.
249	What is meant by degeneracy of genetic code?	Some amino acids are coded by more than one codon.
250	How is the genetic code read in mRNA?	In a contiguous manner without punctuation.
251	What is meant by universal genetic code?	The same codon specifies the same amino acid in most organisms.
252	Which amino acid is coded by UUU?	Phenylalanine (Phe).
253	Which codon acts as the initiator codon?	AUG.
254	Which amino acid is coded by AUG?	Methionine (Met).
255	Name the three stop codons.	UAA, UAG, and UGA.
256	What is a point mutation?	Change in a single base pair in DNA.
257	Which disease is caused by a point mutation in beta-globin gene?	Sickle cell anaemia.
258	In sickle cell anaemia, which amino acid replaces glutamate?	Valine.
259	What is a frameshift mutation?	Mutation caused by insertion or deletion of one or two bases altering the reading frame.
260	What happens when one or two bases are inserted or deleted?	The reading frame changes from that point onward.
261	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.
262	Who proposed the existence of an adapter molecule during translation?	Francis Crick.
263	Why was an adapter molecule considered necessary?	Because amino acids cannot directly read codons.
264	Which molecule acts as the adapter molecule?	tRNA.
265	What was tRNA originally called?	sRNA (soluble RNA).
266	What is present in the anticodon loop of tRNA?	Bases complementary to the codon.
267	What is the function of the amino acid acceptor end of tRNA?	It binds specific amino acids.
268	Are tRNAs specific for amino acids?	Yes, each tRNA is specific for an amino acid.
269	Which special tRNA is required for initiation of translation?	Initiator tRNA.
270	Are there tRNAs for stop codons?	No.
271	What is the secondary structure of tRNA commonly compared to?	Clover-leaf structure.
272	What is the actual three-dimensional shape of tRNA?	Inverted L-shape.
273	What is translation?	Polymerisation of amino acids to form a polypeptide.
274	What is the effect of inserting one base in a genetic code sequence?	It changes the reading frame from the point of insertion.
275	What is the effect of deleting one base from a genetic code sequence?	It alters the reading frame from the point of deletion.
276	What are insertion or deletion mutations causing reading frame changes called?	Frameshift mutations.
277	What happens when three bases are inserted together in a sequence?	One codon is added and the reading frame remains unchanged.
278	What happens when three bases are deleted together?	One codon is removed without altering the reading frame.
279	What is the role of tRNA in protein synthesis?	It acts as an adapter molecule between codons and amino acids.
280	Which part of tRNA reads the genetic code?	Anticodon loop.
281	Which part of tRNA binds amino acids?	Amino acid acceptor end.
282	What is translation?	The process of polymerisation of amino acids to form a polypeptide.
283	What determines the order of amino acids in a polypeptide?	Sequence of bases in mRNA.
284	Which bond joins amino acids during protein synthesis?	Peptide bond.
285	What is required for peptide bond formation?	Energy.
286	What is amino acid activation before translation called?	Charging of tRNA or aminoacylation of tRNA.
287	Which molecule provides energy during amino acid activation?	ATP.
288	What is the cellular factory for protein synthesis?	Ribosome.
289	What are ribosomes made of?	Structural RNAs and about 80 proteins.
290	In inactive state, ribosomes exist as what?	Large and small subunits.
291	What initiates translation on ribosomes?	Binding of the small ribosomal subunit to mRNA.
292	How many sites for amino acid binding are present in the large ribosomal subunit?	Two sites.
293	Which ribosomal component acts as a catalyst for peptide bond formation in bacteria?	23S rRNA.
294	What is a ribozyme?	RNA molecule with catalytic activity.
295	What is a translational unit in mRNA?	Sequence between start codon and stop codon coding for a polypeptide.
296	Which codon acts as the start codon in translation?	AUG.
297	What are untranslated regions (UTRs)?	Sequences in mRNA that are not translated.
298	Where are UTRs located in mRNA?	At both 5' end and 3' end.
299	Why are untranslated regions important?	They are required for efficient translation.
300	Which tRNA recognises the start codon AUG?	Initiator tRNA.
301	During elongation, how do aminoacyl tRNAs bind to mRNA?	By complementary base pairing between codon and anticodon.
302	How does the ribosome move during translation?	From codon to codon along the mRNA.
303	How are amino acids added during translation?	Sequentially according to codons in mRNA.
304	What terminates translation?	Binding of release factor to stop codon.
305	What happens after translation termination?	Complete polypeptide is released from the ribosome.
306	What is regulation of gene expression?	Control of formation of a polypeptide at different levels.
307	At which levels can gene expression be regulated in eukaryotes?	Transcriptional, processing, transport, and translational levels.
308	Which level involves regulation of primary transcript formation?	Transcriptional level.
309	Which level of gene expression regulation involves splicing?	Processing level.
310	Which level of gene expression regulation involves movement of mRNA from nucleus to cytoplasm?	Transport level.
311	Which level regulates protein synthesis directly?	Translational level.
312	Why are genes expressed in a cell?	To perform particular functions.
313	Which enzyme hydrolyses lactose in *E. coli*?	Beta-galactosidase.
314	Into which monosaccharides does beta-galactosidase hydrolyse lactose?	Glucose and galactose.
315	Why is beta-galactosidase not synthesised in absence of lactose?	Because the enzyme is unnecessary without lactose as energy source.
316	What regulates gene expression in simple terms?	Metabolic, physiological, or environmental conditions.
317	Development and differentiation of embryos result from what?	Coordinated regulation of several sets of genes.
318	What is the predominant site for regulation of gene expression in prokaryotes?	Control of transcriptional initiation.
319	What regulates RNA polymerase activity at a promoter?	Accessory proteins.
320	What are regulatory proteins that increase transcription called?	Activators.
321	What are regulatory proteins that decrease transcription called?	Repressors.
322	Which DNA sequences regulate accessibility of promoter regions in prokaryotes?	Operators.
323	Where is the operator region usually located?	Adjacent to promoter elements.
324	Which protein binds to the operator region?	Repressor protein.
325	What is an operon?	Arrangement where polycistronic structural genes are regulated by common promoter and regulatory genes.
326	Which scientists elucidated the lac operon?	Francois Jacob and Jacques Monod.
327	Name some examples of operons mentioned in the text.	lac operon, trp operon, ara operon, his operon, val operon.
328	How many regulatory genes are present in the lac operon?	One.
329	What is the regulatory gene of lac operon called?	i gene.
330	What does the i gene code for?	Repressor of the lac operon.
331	How many structural genes are present in lac operon?	Three.
332	Name the structural genes of lac operon.	z, y, and a genes.
333	What does the z gene code for?	Beta-galactosidase.
334	What is the function of beta-galactosidase?	Hydrolysis of lactose into glucose and galactose.
335	What does the y gene code for?	Permease.
336	What is the function of permease?	Increases permeability of the cell to β-galactosides.
337	What does the a gene code for?	Transacetylase.
338	Why are all three lac operon genes required together?	They are needed for lactose metabolism.
339	What acts as the substrate for beta-galactosidase?	Lactose.
340	Why is lactose called an inducer?	Because it switches the lac operon on and off.
341	What happens to lactose in the presence of permease?	It is transported into the bacterial cell.
342	Why must a low level of lac operon expression always be present?	Otherwise lactose cannot enter the cells.
343	From which gene is the lac operon repressor synthesised?	i gene.
344	How is the lac operon repressor synthesised?	Constitutively (all the time).
345	Where does the repressor protein bind in lac operon?	Operator region.
346	What happens when the repressor binds to the operator?	It prevents RNA polymerase from transcribing the operon.
347	What happens to the repressor in the presence of lactose or allolactose?	It becomes inactivated.
348	What allows transcription of lac operon to proceed?	Inactivation of the repressor by inducer.
349	Which enzyme gains access to the promoter after repressor inactivation?	RNA polymerase.
350	Regulation of lac operon can also be viewed as regulation of what?	Enzyme synthesis by its substrate.
351	Can glucose act as an inducer for lac operon?	No.
352	Can galactose act as an inducer for lac operon?	No.
353	What type of regulation is shown by the lac operon through repressor action?	Negative regulation.
354	Besides negative regulation, what other regulation controls lac operon?	Positive regulation.
355	What does HGP stand for?	Human Genome Project.
356	What determines the genetic information of an organism?	Sequence of bases in DNA.
357	Why should DNA sequences differ between two individuals?	Because individuals differ genetically.
358	Which technological developments made Human Genome Project possible?	Genetic engineering, DNA cloning, and DNA sequencing techniques.
359	In which year was the Human Genome Project launched?	1990.
360	Why is Human Genome Project called a mega project?	Due to enormous genome size, cost, and data involved.
361	What was the estimated sequencing cost per base pair at the beginning of HGP?	US $3 per bp.
362	What was the estimated total cost of HGP initially?	Approximately 9 billion US dollars.
363	Approximately how many books would be needed to store human genome sequence in typed form?	3300 books.
364	Why were high-speed computational devices needed in HGP?	For data storage, retrieval, and analysis.
365	Which new field of biology developed rapidly with HGP?	Bioinformatics.
366	What was one major goal of HGP regarding genes?	Identification of approximately 20,000–25,000 genes.
367	What was one major sequencing goal of HGP?	Determination of 3 billion chemical base pairs in human DNA.
368	What was one database-related goal of HGP?	Storage of information in databases.
369	What was one technological goal of HGP?	Improvement of tools for data analysis.
370	Which sectors were expected to benefit from technologies developed during HGP?	Industries and other sectors.
371	What does ELSI stand for in Human Genome Project?	Ethical, Legal, and Social Issues.
372	Which organizations coordinated the Human Genome Project?	U.S. Department of Energy and National Institute of Health.
373	Which organisation from the UK became a major partner in HGP?	Wellcome Trust.
374	In which year was Human Genome Project completed?	2003.
375	Knowledge of DNA variations among individuals may help in what?	Diagnosis, treatment, and prevention of disorders.
376	Name some non-human organisms whose genomes were sequenced.	Bacteria, yeast, *Caenorhabditis elegans*, *Drosophila*, rice, and *Arabidopsis*.
377	What were the two major approaches used in Human Genome Project methodologies?	Expressed Sequence Tags (ESTs) and Sequence Annotation.
378	What are Expressed Sequence Tags (ESTs)?	Approach focusing on identifying genes expressed as RNA.
379	What is Sequence Annotation?	Sequencing the whole genome and later assigning functions to sequences.
380	Why is genomic DNA fragmented before sequencing?	Because very long DNA molecules cannot be sequenced directly.
381	Into what sizes is genomic DNA converted for sequencing?	Random fragments of relatively smaller sizes.
382	Why are DNA fragments cloned during sequencing?	To amplify each DNA fragment for easier sequencing.
383	Which hosts were commonly used for cloning DNA fragments in HGP?	Bacteria and yeast.
384	What does BAC stand for?	Bacterial Artificial Chromosome.
385	What does YAC stand for?	Yeast Artificial Chromosome.
386	Which scientist also developed methods for amino acid sequencing in proteins?	Frederick Sanger.
387	How were DNA sequences arranged after sequencing?	Based on overlapping regions.
388	Why were overlapping DNA fragments necessary in sequencing?	To align sequences correctly.
389	Why was computer assistance necessary in HGP?	Human alignment of sequences was impossible.
390	What were specialised computer programs used for in HGP?	Sequence alignment and analysis.
391	Which human chromosome was sequenced last?	Chromosome 1.
392	In which year was sequencing of chromosome 1 completed?	May 2006.
393	How many human chromosomes were sequenced in HGP?	24 chromosomes.
394	What are the 24 human chromosomes composed of?	22 autosomes and X and Y chromosomes.
395	Which information helped generate genetic and physical maps of the genome?	Polymorphism of restriction endonuclease sites and microsatellites.
396	What are microsatellites?	Repetitive DNA sequences used in genetic mapping.
397	What is the total size of the human genome?	3164.7 million base pairs.
398	What is the average size of a human gene?	About 3000 bases.
399	Which is the largest known human gene mentioned in the text?	Dystrophin.
400	What is the size of the dystrophin gene?	2.4 million bases.
401	Approximately how many genes are estimated in the human genome?	About 30,000 genes.
402	What percentage of nucleotide bases are identical among humans?	99.9%.
403	For what percentage of discovered genes are functions still unknown?	Over 50%.
404	What percentage of the human genome codes for proteins?	Less than 2%.
405	What makes up a large portion of the human genome?	Repeated sequences.
406	What are repetitive sequences?	DNA sequences repeated many times.
407	What is the significance of repetitive DNA sequences?	They provide information about chromosome structure, dynamics, and evolution.
408	Which chromosome contains the highest number of genes?	Chromosome 1.
409	Approximately how many genes are present on chromosome 1?	2968 genes.
410	Which chromosome contains the fewest genes?	Y chromosome.
411	Approximately how many genes are present on the Y chromosome?	231 genes.
412	What are SNPs?	Single nucleotide polymorphisms.
413	Approximately how many SNP locations were identified in humans?	About 1.4 million locations.
414	What is the significance of SNP information?	Helps identify disease-associated sequences and trace human history.
415	What will understanding DNA sequences help explain in future research?	Biological systems and interconnected gene/protein networks.
416	What percentage of DNA base sequence is identical among humans?	99.9%.
417	Why is DNA sequencing for every individual impractical for comparison?	Because it is a difficult and expensive task.
418	What is DNA fingerprinting?	A quick method to compare DNA sequences of individuals.
419	On what principle does DNA fingerprinting work?	Differences in repetitive DNA sequences.
420	What are repetitive DNA sequences?	Small stretches of DNA repeated many times.
421	How are repetitive DNA sequences separated from bulk genomic DNA?	By density gradient centrifugation.
422	What does the bulk DNA form during density gradient centrifugation?	A major peak.
423	What are the smaller peaks obtained during density gradient centrifugation called?	Satellite DNA.
424	On what basis is satellite DNA classified?	Base composition, segment length, and number of repetitive units.
425	Name different categories of satellite DNA.	Microsatellites and minisatellites.
426	Do repetitive DNA sequences code for proteins?	No.
427	What property of repetitive DNA forms the basis of DNA fingerprinting?	High degree of polymorphism.
428	Why is DNA fingerprinting useful in forensic science?	DNA from different tissues of an individual shows the same polymorphism.
429	Which tissues can be used for DNA fingerprinting?	Blood, hair follicle, skin, bone, saliva, and sperm.
430	Why is DNA fingerprinting useful in paternity testing?	DNA polymorphisms are inherited from parents to children.
431	What is DNA polymorphism?	Variation at the genetic level due to mutations.
432	How do new mutations arise?	In somatic or germ cells.
433	Which mutations can spread in a population?	Germ cell mutations that do not impair reproduction.
434	When is a variation called DNA polymorphism?	When a variant occurs in a population with frequency greater than 0.01.
435	In which DNA regions are mutations more likely to accumulate without harmful effects?	Non-coding DNA sequences.
436	Why do mutations accumulate more in non-coding DNA?	Because they usually do not affect reproductive ability.
437	What role do DNA polymorphisms play in evolution?	They contribute to variability and speciation.
438	Who developed the DNA fingerprinting technique initially?	Alec Jeffreys.
439	Which type of satellite DNA was used as a probe by Alec Jeffreys?	Variable Number Tandem Repeats (VNTRs).
440	What does VNTR stand for?	Variable Number of Tandem Repeats.
441	Which technique was initially used in DNA fingerprinting?	Southern blot hybridisation.
442	Which probe was used in Southern blotting during DNA fingerprinting?	Radiolabelled VNTR probe.
443	What is the first step in DNA fingerprinting?	Isolation of DNA.
444	Which enzymes are used to digest DNA during fingerprinting?	Restriction endonucleases.
445	Which technique separates DNA fragments in DNA fingerprinting?	Electrophoresis.
446	To which membranes are DNA fragments transferred during blotting?	Nitrocellulose or nylon membranes.
447	Which process uses labelled VNTR probes in DNA fingerprinting?	Hybridisation.
448	Which technique detects hybridised DNA fragments?	Autoradiography.
449	To which class of satellite DNA does VNTR belong?	Minisatellite DNA.
450	Why do VNTRs show high polymorphism?	Because the copy number varies among chromosomes and individuals.
451	Why does VNTR vary among individuals?	Because copy number of repeats differs among chromosomes and individuals.
452	What is the size range of VNTRs?	0.1 to 20 kb.
453	What pattern is produced after hybridisation with VNTR probes?	Bands of differing sizes.
454	Why does each individual show a unique DNA fingerprint pattern?	Due to differences in VNTR copy numbers.
455	In which individuals is DNA fingerprint pattern identical?	Monozygotic (identical) twins.
456	Which technique increased the sensitivity of DNA fingerprinting?	Polymerase Chain Reaction (PCR).
457	Why is PCR useful in DNA fingerprinting?	Because DNA from a single cell is sufficient for analysis.
458	Besides forensic science, where else is DNA fingerprinting useful?	Population genetics and genetic diversity studies.
459	What is the major function of DNA?	Storage of genetic information.
460	What is the major role of RNA in cells?	Transfer and expression of genetic information.
461	Which nucleic acid is chemically and structurally more stable?	DNA.
462	Which molecule is believed to be the first genetic material?	RNA.
463	What is the hallmark of double-stranded DNA structure?	Hydrogen bonding between complementary bases.
464	Which bases pair through two hydrogen bonds?	Adenine and Thymine.
465	Which bases pair through three hydrogen bonds?	Guanine and Cytosine.
466	Why are the two DNA strands complementary?	Due to specific base pairing.
467	How does DNA replicate?	Semiconservatively.
468	What guides semiconservative DNA replication?	Complementary hydrogen bonding.
469	During transcription, what acts as the template for RNA synthesis?	One strand of DNA.
470	Why can bacterial mRNA be translated immediately after transcription?	Because it is already functional and requires no processing.
471	What interrupts coding sequences in eukaryotic genes?	Introns.
472	What are coding sequences in eukaryotic genes called?	Exons.
473	Which process removes introns from RNA?	Splicing.
474	How is the genetic code read during translation?	In triplets.
475	Which molecule reads the genetic code during translation?	tRNA.
476	What role does tRNA play in translation?	Adapter molecule between codons and amino acids.
477	What is the site of protein synthesis in cells?	Ribosome.
478	Which RNA acts as a catalyst during peptide bond formation?	rRNA.
479	What is a ribozyme?	Catalytic RNA molecule.
480	Why is translation considered to have evolved around RNA?	Because RNA performs catalytic and informational roles.
481	Why must transcription and translation be tightly regulated?	Because they are energetically expensive processes.
482	What is the primary step for regulation of gene expression in bacteria?	Regulation of transcription.
483	What are operons?	Groups of genes regulated together under a common promoter.
484	Which operon is the prototype operon in bacteria?	Lac operon.
485	Which metabolic process is controlled by lac operon?	Lactose metabolism.
486	What regulates the lac operon?	Amount of lactose in the medium.
487	What was the aim of Human Genome Project?	Sequencing every base in the human genome.
488	What is DNA fingerprinting based on?	DNA polymorphism.
489	What is polymorphism?	Variation in DNA sequences among individuals.
490	Name major applications of DNA fingerprinting.	Forensic science, genetic biodiversity studies, and evolutionary biology.
491	Group the following as nitrogenous bases and nucleosides: Adenine, Cytidine, Thymine, Guanosine, Uracil, Cytosine.	* Nitrogenous bases: Adenine, Thymine, Uracil, Cytosine, * Nucleosides: Cytidine, Guanosine
492	If double-stranded DNA contains 20% cytosine, what percentage of adenine will be present?	30%.
493	Which base pairs with cytosine in DNA?	Guanine.
494	What is the complementary strand for the DNA sequence 5'-ATGCATGCATGCATGCATGCATGCATGC-3'?	3'-TACGTACGTACGTACGTACGTACGTACG-5'.
495	If the coding strand sequence is 5'-ATGCATGCATGCATGCATGCATGCATGC-3', what will be the mRNA sequence?	5'-AUGCAUGCAUGCAUGCAUGCAUGCAUGC-3'.
496	Which property of DNA double helix suggested semiconservative replication?	Complementary base pairing between strands.
497	What is semiconservative DNA replication?	Each daughter DNA molecule contains one parental strand and one newly synthesised strand.
498	Which nucleic acid polymerase synthesises DNA using DNA as template?	DNA-dependent DNA polymerase.
499	Which nucleic acid polymerase synthesises RNA using DNA as template?	DNA-dependent RNA polymerase.
500	Which experiment proved DNA as genetic material?	Hershey-Chase experiment.
501	How did Hershey and Chase distinguish DNA from protein?	Using radioactive phosphorus for DNA and radioactive sulfur for proteins.
502	What is repetitive DNA?	DNA sequences repeated many times in the genome.
503	What is satellite DNA?	Repetitive DNA separated as small peaks during density gradient centrifugation.
504	What is the function of mRNA?	It acts as a template for protein synthesis.
505	What is the function of tRNA?	It transports amino acids and reads genetic code through anticodon.
506	What is the template strand in transcription?	DNA strand with polarity 3'→5' used for RNA synthesis.
507	What is the coding strand in transcription?	DNA strand with same sequence as RNA except thymine replaces uracil.
508	What is the function of a promoter?	It provides the binding site for RNA polymerase.
509	What is the function of tRNA?	Adapter molecule linking codons to amino acids.
510	What are exons?	Coding sequences that appear in mature RNA.
511	What is transcription?	Copying of genetic information from DNA into RNA.
512	What is polymorphism?	Variation in DNA sequence among individuals.
513	What is translation?	Polymerisation of amino acids to form proteins according to mRNA sequence.
514	What is bioinformatics?	Use of computational tools for storage, retrieval, and analysis of biological data.