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B.I Molecular Biology
Multiple choice questions
1. The nucleic acids are acidic in nature due to the presence of
a) Nitrogenous bases
b) Pentose sugarsc) Phosphate groups
d) Hydrogen bonds
Obj/
Act. Verb!Ditr. Level
U
Establishes
relationship
Average
2. A monocyclic nitrogenous base present in DNA is
a) Adenine
b) Guaninec) Cytosine
d) Uracil
U
Correlates
Average
3 . The chemical bond formed between pentose sugar and phosphate U
group in DNA molecule is Establishes
a) Glycosidic bond relationship
b) Hydrogen bond
c) Phosphodiester bond
d) Ester bond
4. The components ofUridylic acid are
a) uracil + riboseb) uracil + ribose + phosphatec) uracil + phosphated) uracil+ any acid
U
Batablishes
relationship
Difficult
5. DNA is not present in
a) Episome
b) Chondriosome
c) Nucleoid .
d) Dictyosome
K .Recognises
Difficult
6. The short lived highly unstable RNA is
a) m-RNA
b) t-RNAc) r-RNA
d) mitochondrial RNA
K
Recalls
Easy
7 . A bacterium having radioactive DNA strands is allowed to A
replicate in non-radioactive culture medium for two generations. Analyses. Difficult
The percentage of ra~ioactive bacteria in second generation is
1 3 1
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The percentage of radioactive bacteria in second generation is
a) 25%
b) 50%c) 75%
d) 100%
8. The codon recognition ann oft-RNA is
a) amino acid a r mb) DHUarm
c) T'PCarm
d) Anticodon arm
U
Establishes
relationship
Average
9. "The enzyme required for the synthesis ofr-RNA in Eukaryotes is
a) RNA primase
b) RNApolyIc) RNA poly II
d) RNA poly III
u .Establishes
relationship
Average
10. The most acceptable gene hypothesis is
a) one gene-one character
b) one gene-one enzyme
c) one gene-one protein
d) one cistron - one polypeptide
K
Recalls
Difficult
"II. The ds DNA having 21% Thymine will have
a) 21% Cytosine
b) 29% Guanine
c) 79% Adenined) 29% Adenine
A
Analyses
Difficult
12. The enzyme involved in the formation of Okazaki fragments inprokaryotes is
a) DNA poly I
b) DNA poly II
c) DNA poly III
d) RNA poly II
KRecalls
Difficult
13. Which of the following is the correct representation of U
semiconservative replication of DNA ? ~, Discriminatesa) . "Difficult
5'
3'
b) 3'
, 5' \
5 ':: ,;r"
, : _ . . . . ; f
3 '
138
.I'
5 '"
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c)
U
Establishes
relationship
Difficult
d)
14. DNA (I») mRNA (/I») protein.
In the above flow chart, (i) and (ii) denote
a) translation and transcription
b) transcription and translation
c) replication and transcription
d) transcription and replication
15. An amino acid which can be coded by three codons exhibits
a) 3-fold degeneracy
b) codon degeneracy
c) commaless codon
d) 2-fold degeneracy
K
Recalls
Difficult
~
16. The enzyme coded by Lac - tgene in E. coli isa)
rl-galactosidase
b) rl - galactoside permease
c) rl- galactoside transacetylase
d) Thiogalactoside transacetylase
U
Correlates
Easy
17. Which of the following shows similar nucleotide sequence on m- U
RNA with the exception of Uridylic acid ? AnalysesDifficult
a) Antisense strand of DNA
b) Sense strand of DNA
c) Anticodons oft-RNA
d) Template of DNA
18. What is the number of amino acids present in a nascent Upolypeptide translated from the m-RNA having 1011 nucleotides Establishes
in the open reading frame? relationshipDifficult
a) 1010
b) 1009
c) 337
d) 336
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19. Wobble hypothesis supports
a) universality of genetic code
b) degeneracy of genetic code •c) unambiguity of genetic code
d) colinearity of codon
Very short answer questions . .
20. Name the scientist who discovered nucleic acids.
21. Name the scientist who coined the term nucleic acid.
22. Name the nitrogenous base present in DNA but not in RNA.
23. Name the pentose sugar present in DNA.
24. Name the pentose sugar present in RNA.
25. Name the pyrimidine base present in both the DNA and RNA.
26. What is a Nucleoside?
27. What is a Nucleotide?
28. Name the monomeric unit of a nucleic acid IDNA I RNA ?
(anyone of the three to be mentioned in a question)
29. Name the components of uridylic acid.
30. Name the components of deoxycytidine.
U
Establishes
relationshipAverage
K
Recalls
Easy
K
Recalls
E a s y
K
Recalls
Average
K
Recalls
E a s y
K
Recalls
Easy
KRecalls
Average
K
Defines
E a s y
K
Defines
E a s y
K
Recalls
E a s y
U
Identifies
Average
U
Identifies
E a s y
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31. Name the chemical bond formed between nitrogenous base and U
Identifies
E a s ypentose sugar in a nucleotide.
32. Name the chemical bond formed. between pentose sugar and U
phosphate group in a nucleotide. IdentifiesAverage
33. Name the chemical bonds formed between the complementary UIdentifies
Averagenitrogenous bases in DNA.
34. How many nuclelotide pairs are present in one complete turn of K
DNA helix? RecallsE a s y
35. What is the percentage of adenine in a ds DNA, having 30% of S
cytosine? SolvesDifficult
36. Mention the functions of Unwindase / Gyrase / RNA primase/ DNA K
polymerase I / DNA Polymerase II / DNA Polymerase III / SSBP / Recalls
Windase / Topoisomerase / DNA ligase. E a s y
(Function of each enzyme is a separate question).
37. What is a lagging strand of DNA ? K
Defines
Difficult
38. What is a leading strand of DNA ? K
DefinesDifficult
39. What is ORI site? K
Defines
Average
40. What are Okazaki fragments? K
Defines
Average
41. What is RNA primer? K
Defines
Average
42. Name the short lived! unstable / least occurring type of RNA.
(Each alternative must be a separate question).
K
Recalls
E a s y
43. Name the soluble RNA / Adapter RNA / smallest RNA / RNA that K
carries amino acids. Recalls
(Each alternative must be a separate question). E a s y
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44. Name the most abundant RNA I largest RNA.
,(Each alternative must be a separate question).
K
Recalls
E a s y
45. Name the scientist who proposed the clover leaf (trifoliate) model of K
t-RNA. RecallsE a s y
46. Which is the amino acid binding site of t-RNA ? U
Identifies
Average
47. Which is the ribosome recognition site of t - RNA ? U
Identifies
Average
48. Which is the decoding (loop) site oft-RNA? U
Identifies
Average
49. Name the scientist who discovered m-I~NA. K
Recalls
E a s y
50. Mention the function oft-RNA. U
Explains
Average
51. Mention one function of m-RNA. U
Explains
Average
52. Mention one function of r-RNA. U
Explains
Average
53. Which part of the t-RNA is recognized by aa-t-RNA synthetase U
enzyme? ExplainsAverage
54. What is monocistronic m-RNA ? K
Defines
Average
55. What is polycistronic m-RNA ? K
Defines
Average
56. What is Hn-RNA I heterogeneous nuclear RNA ? K
Recalls
Average
57. Name the scientist who proposed the fine structure of gene. K
Recalls
E a s y
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58. What are split genes? K
Defines
Average
59. What are unsplit genes? K
Defines
Average
60. Define Cistron / Muton / Recon / Replicon / Operon / Lac - Operon! K
Codon / Anticodon. Defines
(Each alternate term must be a separate question).Easy
61. Define initiator codon. K
Defines
Average
62. Name the most common initiator codon. K
RecallsEasy
63. Name the amino acid coded by initiator codon. K
Recalls
Easy
6 4 . Name the enzyme that activates amino acid during protein synthesis. K
Recalls
Average
65. Name the enzyme that helps in the formation of peptide bonds K
between amino acids during protein synthesis. RecallsAverage
66. Define transcription. K
Defines
Easy
67. Define Translation. K
Defines
Easy
68. Name the enzyme coded by Lac z / Lac y / Lac a genes of lac- K
operon. Recalls
(Each alternative must be a separate question).Average
69. Which gene of operon produces the repressor protein? K
Recalls
Easy
70. Name the inducer of Lac-operon in E.coli. K
Recalls
Easy
71. Name the scientists who proposed operon concept. K
Recalls
Easy
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72. Which enzyme catalyses the synthesis of DNA using a RNA K
template? Recalls
Easy
73. Name the codon with double function. K
Recalls
Average
Give reasons for the following (Questions 74 - 92)
74. DNA is acidic in nature / nucleotides are acidic in nature. U
Establishes
relationship
Average
75. DNA replication is semi conservative I semi discontinuous! bi- U
directional. ExplainsDifficult
(Each alternative must be a separate question.)
76. How is DNA replication initiated? U
Establishes
relationship
Difficult
77. Chargoff's base rule is not applicable for RNA. A
Analyses
Difficult
78. G - C Pairing is stronger than A - T Pairing. U
Establishes
relationshipDifficult
79. The nucleotide ratio in RNA is not usually constant (or) highly APredicts
Difficultvariable.
80. The processed m-RNA in eukaryotes is shorter than its gene or in A
Eukaryotes the length of processed m-RNA does not match the PredictsDifficult
length of its gene.
81. Prokaryotic gene is an unsplit gene. U
Correlates
Difficult
82. Eukaryotic gene is a split gene. U
Correlates
Difficult
83. UAA is a terminator codon (non-sense codon) U
Establishes
relationship
Difficult
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84. AUG is the initiator codon. U
Gives reasons
Difficult
85. 61 codons code for only 20 amino acids. U
Gives reasons
Difficult
86. Lac-operon switches off in the absence of inducer
E.coli.
(lactose) in UGives reasons
Difficult
87. When the extract of heat killed S-cells of Pneumococcus treated U
with DNA is introduced into the culture of live R-cells, there is no Analyses
transformation.Difficult
88. Codons are universal. A
Gives reasonsDifficult
89. Codons are redundantl sensible. A
Gives reasons
Difficult
90. All polypeptides start with methionine as first amino acid, but all A
proteins do not have methionine. Analyses
Difficult
91. Methionine is always the first amino acid brought to the site of A
protein synthesis. Analyses
Difficult
92. Redundancy concept of genetic code does not apply to all amino A
acids. Analyses
Difficult
Short answer questions
93. Draw a neat and labeled diagram ofm-RNA. S ,
Drawing
Average
94. Mention any four structural differences between DNA and RNA. U
Compares
Average
95. Name the nitrogenous bases ofDNAIRNA.
(Each alternative must be a separate question)
K
Recalls
Average
96. Name the pyrimidines present in DNAIRNA. K
Recalls
Average
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97. Mention the types of nucleotides in DNA.
98. Mention the types of nucleotides in RNA.
99. List two differences between a nucleoside and nucleotide.
100 Draw a neat and labeled diagram of the DNA molecule.
101. Draw a neat and labeled diagram oft-RNA molecule.
102. Mention two functions each for DNA and RNA.
103. List four functions of DNA.
104. Mention two differences between prokaryotic and eukaryotic genes.
105. List four functions of RNA.
106. Mention 4 characteristic features of genetic code.
107. What are terminator codons? Mention two of them.
108. What are non-sense codons? Name any two.
109. Mention two structural and two control genes of lac operon.
110. Name the three types of RNA in a eukaryotic cell.
K
Recalls
Average
K
Recalls
Average
U
Compares
Average
S
Drawing
Average
S
Drawing
Average
U
Compares
Average
K
Lists
Average
U
Compares
Easy
K
Lists
Average
K
Mentions
Average
K
Recalls
Average
K
RecallsAverage
KRecalls
Average
K
Recalls
Easy
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Ill. Explain the two steps in the activation of amino acid during protein U
synthesis. ExplainsAverage
112. During translation, if the codon is AUG then
i) what is the anti-codon present on the complementary t-
RNA?
ii) Name the amino acid carried by this t-RNA.
U
Identifies
Average
113. How many amino acids are present in a nascent polypeptide S
decoded from the m-RNA with the reading frame having 1002 Solves
nucleotidesl 334 codons? Average
Long answer questions
114. Describe the double helical model of DNA with a neat labeled
diagram.
U,SSkill,
explains
Difficult
115. Explain the semiconservative replication of DNA molecule with the U,S
help of labeled diagram. Skill,explains
Difficult
116. Describe the clover leaf model of t-RNA molecule with a neat U, S
labeled diagram. Draws,explains
Difficult
117. Explain the experiment of O.T. Avery that proved DNA as the U
genetic material. ExplainsDifficult
118. List five differences between DNA and RNA. U
Compares
Average
119 Explain five characteristic features of the genetic code. U
Explains
Average
120 Explain the process of Transcription with the help of labeled
diagram.
U,S
Draws,explains
Average
121. Explain amino acid activation and chain initiation steps of protein U
synthesis. ExplainsDifficult
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122. Mention the genes of Lac-operon and their functions. U
Explains
Average
123. Explain the structure ofm-RNA with a neat labeled diagram. U,S
Draws,
explains
Difficult
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ANSWERS
Multiple choice answers (one mark each)
1. c
2. c
3. d
4. b
5. d
6. a
7. b
8. d
9. b
10. d
11. b
12. c
1 3 . c
14. b
15. a
16. a
17. b
18. d
19. b
Very short answers (one.mark each)
20. Friedrich Meischer
21. Altmann
22. Thymine
23. Deoxyribose
24. Ribose
25. Cytosine
26. It is a combination of nitrogenous base and pentose sugar.
27. It is a combination of nitrogenous base, pentose sugar and phosphate.
28. Nucleic acid - Nucleotide
DNA - Deoxyribose nucleotide
RNA - Ribose nucleotide
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29. Uracil, ribose sugar and phosphate.
30. Cytosine and deoxyribose sugar.
31. N - ~ - Glycosidic bond IN ~ glycosylic bond
32. Ester bond I phospho ester bond.
33. Hydrogen bonds.
34. Ten pairs
35. 20% of adenine
36. Unwindase - unwinding the two strands of DNA molecule during proteinsynthesis.
Gyrase - relieves the tension of supercoiled regions of DNA.
RNA primase - produces RNA primers to initiate (replication)- polynucleotide
formation complementary to the template strands of DNA.
DNA polymerase I - replaces RNA primers by polydeoxy ribonucleotide
fragments.
DNA polymerase II - it helps in proofreading and DNA repairing.
DNA polymerase III - catalyses the polymerization of deoxy ribonucleotides in
5' - 3' direction.
SSBP (Single Strand Binding Protein) - these are helix destabilizing proteins
that keeps two strands of DNA in separated condition during replication.
Windase - it helps in winding of the polynucleotide strands of DNA.
Topoisomerase - breaks and reseal the DNA strands.
DNA ligase - joins the fragments of DNA or Okazaki fragments.
37. It is the strand of DNA formed discontinuously against the sense strand during
replication.
38. It is the daughter strand of DNA formed continuously towards the replication
fork during replication.
39. The point at which the uncoiling of DNA begins during replication is calledOR! site. .
40. Short single stranded discontinuous DNA fragments formed away from the
replication fork during replication.
41. It is a short fragment of RNA formed by RNA primase at the beginning of DNA
replication.
42. m-RNA Imessenger RNA
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43. t-RNA / Transfer RNA.
44. r-RNA / ribosomal RNA.
45. Robert W. Holley.
46. CCA 3'OH end / 3' OH end oft-RNAICCA end.
47. T \fIC loop / T -loop
48. Anticodon / NODOC loop
49. Volkin
50. It transfers amino acid to the site of protein synthesis! Transfer of aa to the siteof protein synthesis.
51. It carries the genetic message from DNA (genes) in the form of codons for the
synthesis of a polypeptide or protein.
52. It is a structural component of ribosomes that helps in translation process of
protein synthesis.
53. Dihydroxy Uridine Loop / DHU loop
54. The m-RNA transcribed by a single cistron / The m-RNA that carries codes for
a single polypeptide.
55. The m-RNA transcribed from many cistrons / The m-RNA that carries codes
for many polypeptides.
56. The RNA transcribed by eukaryotic gene having coding exons and non-coding
introns.
57. Seymour Benzere
58. The genes having coding exons and non-coding introns.
59. The genes having only coding sequences (exons) are called Unsplit genes.
60. Cistron : It is the functional unit of gene that codes for a single polypeptide.
Muton : It is a unit of cistron that undergoes mutation.
Recon: It is a unit of cistron that undergoes recombination.
Replicon : It is a unit of DNA that undergoes replication.
Operon : It is a co-ordinated assembly of regulatory and structural genes meant
to perform a specific metabolic activity.
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Lac-operon: It is an operon concerned with lactose metabolism found in E.coli
bacterium.
Codon : A unit of three nucleotides on m-RNA that codes for a specific amino
acid during protein synthesis.
Anticodon: A unit of three nucleotides on t-RNA that decodes the codon of m-
RNA.
61. The codon on m-RNA where the formation of polypeptides is initiated.
62. AUG.
63. Methionine! f-methionine
64. Amino acyl t-RNA synthetases.
65. Peptidyl transferase
66. The process of formation of m-RNAlRNAs from the antisense strand of DNA
with the help of RNA polymerase.
67. The process of decoding of codons on m-RNA into a sequence of amino acids
forming a polypeptide chain.
68. a) Lac x - J 3 galactosidaseb) Lac y - J 3 galactoside permease (m - protein)c) Lac a - J 3 galactoside transacetylase (thiogalactoside transacetylase)
69. Regulator gene
70. Lactose
71. Francis Jacob and Jacques Monad.
72. Reverse transcriptase (RNA dependent DNA polymerase)
73. AUG.
74. Due to the presence of phosphate group.
75. Semi conservative: The parental strands are conserved in daughter DNA
molecules OR the daughter DNA molecules have one parental and one new
strand.
Semi discontinuous: Because the leading strand is produced continuously and
lagging strand is produced discontinuously.
Bi-directional: Because the leading strand is produced towards the replication
fork and lagging strand is produced away from the replication fork.
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The two strands of DNA molecule are antiparallel and the enzymes are direction
specific.
76. RNA primer initiates the formation of polynucleotide in 5' ~ 3' direction by
providing pre-existing 3' - OH end.
77. Because it is single stranded.
78. Because 3H bonds bind G and C but only 2H bonds bind A and T.
79. Due to the absence of complimentary base pairing it is single stranded.
80. Because the eukaryotic gene is a split gene and the transcribed and processed m-
RNA has intron portions.
81. Because it contains continuous coding sequences or exons.
82. Because it contains coding exons and non-coding introns.
83. Because it terminates protein synthesis as it does not code for any amino acid.
84. Because it initiates the process of polypeptide synthesis / protein synthesis.
85. Due to the property of genetic code called degeneracy, most amino acids are
coded for by more than one codon. Hence the number of codons exceed the
number of amino acids.
86. The repressor binds to operator and prevents transcription.
87. Because heat hydrolyses DNA.
88. A codon codes for the same amino acid in all organisms.
89. Redundant - A single amino acid can be coded by 2 or 3 codons.
Sensible - A codon codes for a specific amino acid.
90. Although methionine is the first amino acid translated, it is removed
subsequently during polypeptide maturation in many proteins.
91. The initiator codes - AUG codes for methionine.
92. Some amino acids like tryptophan and methionine have one codon each.
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Short answers
93. Diagram with any 4 labels.
m-RNA, codon, 3' end, 5' end, nucleotide
( Y 2 X 4 = 2 marks)
94. DNA
• Double stranded molecule.
• It contains adenine guanine
cytosine and thymine.
• Pentose sugar is deoxyribose.
• It contains large number of
nucleotides.
• Chains are antiparallel.( Y 2 x 4 = 2 marks)
RNA• Single stranded molecule.
• It contains adenine, guanine, cytosine
and uracil.
• Pentose sugar is ribose.
• It contains fewer nucleotides.
• Being a single chain does not exhibit
antiparallel nature.
95. DNA - Adenine I Guanine I Cytosine and Thymine
RNA - Adenine IGuanine ICytosine and Uracil
( Y 2 + Y 2 + Y 2 + Y 2 = 2 marks.)
96. DNA - Cytosine (C) and Thymine (T)
RNA - Cytosine (C) and Uracil (U)
Pyrimidines of DNA -1mark, RNA -1mark = 2 marks)97. a) Deoxy adenosine monophosphate I dAMP/ d-Adenylic acid
b) Deoxy Guanosine monophosphatel dGMP I d-Guanylic acidc) Deoxy Cytidine monophosphate/ dCMPI d-Cytidylic acid
d) Deoxy thymidine monophosphate/ dTMP / d-Thymidylic acid.
( Y 2 + Y 2 + Y 2 + Y 2 = 2 marks.)
98. RNA nucleotides are
i) Adenosine monophosphate IAMP IAdenylic acid
ii) Guanosine monophosphate / GMP / Guanylic acid
iii) Cytidine monophosphate I CMP I Cytidylic acid
iv) Uridine monophosphate / UMP / Uridylic acid
(~+ Y 2 + ~+ ~=2marks.)
99. Nucleoside• It is made up of
nitrogenous base and
pentose sugar.
• It is slightly alkaline.
(1 + 1 = 2 marks.)
Nucleotide• It is made up of nitrogenous base,
pentose sugar and phosphate.
• It is acidic in nature.
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100. Diagram with any 4 labels.
Helix 1, helix 2, nitrogenous base, deoxyribose sugar, phosphate, phospho-di-
ester bond, 3' end, 5' end.
(Diagram - 1mark, labels (any four) - 1= 2 marks)
101. Diagram with any 4 labels.
CCA, 3' end, 5'end, DHU arm, 1'PC arm, anticodon arm, anticodon, central
petal, lateral petals (arms), small arm, amino acid arm.
(diagram - 1, labels (any four - I =2 marks)
102. DNA
• It is a hereditary material.
• It is self replicating.
• Itdirects protein synthesis.
• Itcan produce RNA.
( Y l x 2 x 2 =4 marks)
RNA
• It is hereditary material in a few viruses.
• It is synthesized against a DNA
template.
• It assists in protein synthesis.• RNA usually does not produce DNA.
103. • It is the genetic material.
• It is the master molecule of metabolic activities as it contains codes for
all the proteins.
• It shows autocatalytic function.
• It can undergo mutations.
• It synthesizes different types of RNA by transcription.
( Y l x 4 =2 marks)
104. Prokaryotic gene
• Transcribes polycistronic
m-RNA.
• Unsplit gene.
• Onlyexons
( Y l x 2 x 2 =2 marks)
Eukaryotic gene
~ Transcribes monocistronic m-RNA.
• Split gene.
• Introns and exons
105. • Genetic RNA carries hereditary characters.
• m-RNA carries the message from DNA (gene) in the form of tripletcodons.
• t-RNA carries specific amino acids to the site of ribosome.
• r-RNA helps in binding of m-RNA and t-RNA to the ribosomal surface.
(Y l x 4 = 2 marks)
106. Any four of the following:
• Genetic code consists of triplet codons.
• Genetic code is unambiguous.
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• Genetic code is universal.
• Genetic code is degenerate.
• AUG is the initiating codon.
• It is commaless.
• 61 out of 64 codons code for amino acids.
• 3 codons are terminator codons - UAA, UAG and UGA.
( ~ x 4= 2 marks)
107. The codons that terminate the polypeptide chain synthesis (translation) arecalled terminator codons.
UAA, UAG and UGA (Ochre, Amber, Opal)
(Definition - 1, two examples = Y2+ Y2= 2 marks)
108. The codons that do not code for any amino acids are called non-sense codons.Also called chain terminator codons.
Ochre IAmber I opal or UAA' I UAGI UGA.
(Definition -1mark, examples - ~ + ~ - 1 = 2 marks)
109. • Structural genes - Lac - Z, Lac - Y, Lac - A (any 2)
• Control genes - Regulator (R), Promoter (P) and Operator (0) (any two)
(structural genes - Y 2 + Y2;control genes Y2+ Y 2 =2 marks)
110. • Genetic RNA
• m-RNA
• t-RNA
• r-RNA(All 3 =2 marks; Y2mark less for each type that is not mentioned.
111. Amino acid +ATPA min oacy/
synthetase ) aminoacyl adenylate + PP
The amino acyladenylate combines with specific t-RNA molecule to form
aminoacyl t-RNA.
Aminoacyl adenylate + t-RNA ---» aminoacyl t-RNA + AMP
(each step 1mark x 2 =2 marks)
112. i) UAC
ii) Methionine(1 + 1=2 marks)
113. 333 amino acids.
156
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Long answers
114. Diagram and any 4 correct labels• Antiparallel
• complementary
• helically coiled
• 2 polydeoxyribonucleotide strands.
• Double stranded
• Left handed helix
• Backbone formed by deoxyribose sugar and phosphate
groups held together by phosphodiester bond.
• The complementary base pairing (A =T, C = = G) between the
helices is by hydrogen bonds.
• One complete turn measuring 34Aohaving a major groove
and a minor groove.(Diagram - 2, labels (at least 4) - I, explanation (6 points) = _ 2 = 5
marks)
115. Diagrams and any six points.
• ORI site• Unwinding by the enzyme unwindase I helicase• SSBP destabilizes the strands and stress is relieved in
supercoiled regions by gyrase.
• RNA primase - RNA primer.
• Leading strand formation towards replication fork - DNA
poly Ill.
• Formation of Okazaki fragments - away from replication
fork.
• Replacement of RNA primers - DNA poly I
• DNA fragments are joined by DNA ligase.
• Proofing of strands (DNA poly II and Topoisomerase)
• Winding of parental strands with lagging and leading strands
to produce 2 similar daughter molecules by the enzyme
windase.
(Diagrams - 2, labels (any four) - I, explanation (6 points) - 2 = 5
marks)
116. • Single stranded I discovery I trifoliate• 3'OH end having terminal nucleotides - CCA
• 5' end ends in G
• T loop (T",C loop)
• DHU loop
• Anticodon loop
• Variable short arm
(Diagram - 2, labels (any 4) - 1, 4 points x ~ _2 =5 marks)
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117. • Based on the Griffith's experiment OT Avery, Mccleond,
Mccarty, carried out experiments which proved that the
transforming principle is DNA.
Separate the Organic molecules from the extract of S-strain.
(1mark for each step x 5 = 5 marks)
118. DNA
• Mostly double stranded
• Nucleotides are AGCT
• Deoxyribose sugar
• It acts as the templatetranscription.
• B-DNA, A-DNA and Z-DNA types - coexist in a
DNA molecule.
RNA
• Single stranded except insome viruses.
• Nucleotides are AGCU.
for·. Ribose Sugar
• It is involved in the process
of protein synthesis.• Many types like m-RNA, r-RNA, t-RNA.
(DNA points ~ x 5 = 2 ~; RNA points ~ x 5 = 2 ~ = 5 marks)
119 Any five of the following:
• Genetic code consists of triplet codon.
• Genetic code is unambiguous.
• Genetic code is universal.
• Genetic code is degenerate.
• AUG is the initiating codon.
• It is commaless.
• 61 out of 64 codons code for amino acids.
• 3 codons are terminator codons - UAA, UAG and UGA.
(Each feature + explanation ( ~ + ~ = 1markx 5 =5 marks)
120 • Unwinding by unwindaselhelicase
• Sense strand
• Antisense strand
• Roles of RNA polymerases m-RNA
• Rewinding of separated strands.(Diagrams - 2, labels (any 4) - I, explanation - 2 =5 marks)
121. Amino acid activation: 2 steps - 1 mark each.amin o a c y l
Amino acid +ATP s y n t h e t a s e ) amino acyladenylate + pp
Aminoacyl adenylate + t-RNA s y : ; : ~ t . ! aminoacyl t-RNA + AMP
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Chain Initiation:
• Binding of smaller sub-unit of ribosome to 5' end of m-RNA.
• Binding of methionine - tRNA to the initiating codon of m-RNA with the help oflF, IF2, IF3and ATP.
• Attachment of larger sub-unit of ribosome.
Diagram must show smaller unit and larger units of ribosome, m-
RNA, aa, t-RNA with UAC anticodon binding to AUG codon on m-
RNA.
(Amino acid activation - 1 mark, diagram of initiation steps - 2,
explanation - 2 =5 marks)
122. • Mentioning of 5 genes (~ mark each.)
• Mentioning of5 functions (~mark each.) =2 Y 2 marksTotal =5 marks
123. Structure of m-RNA:
• 5'P leader and with cap.
• 3' OH end with poly A tail
• Leader sequence
• Initiator codon region - reading frame
• Variable coding region - reading frame
• Terminator codon region - reading frame
(Diagram - 2 marks, explanation (6 points x ~ - 3)=5 marks)
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