Download Note: all of these sentences are true.

No of page 3
Q1: Write ‘true’ or ‘false’
Exercise No. 2
(Difficult 1)
Note: all of these sentences are true.
1. The structure of DNA is of consist of Nucleotides.
2. Nucleotides consist of nitrogenous base , a five-carbon sugar (ribose (in RNA) or
deoxyribose (in DNA)), and phosphate group.
3. The sugar found in DNA is deoxyribose.
4. The sugar found in DNA is ribose.
5. In DNA the 5'-end with free phosphate and a 3'-end with free hydroxyl.
6. The sequence of nucleotides is read 5'→3„.
7. Nucleases or exonucleases can be degraded DNA or RNA by hydrolyzed Phosphodiester
linkages between nucleotides.
8. Minor and major grooves provide access for: the binding of regulatory proteins and as
Certain anticancer drugs.
9. actinomycin D, exert their cytotoxic effect by a. intercalating into the narrow groove of the
DNA double helixand and b. interferes with the movement of RNA polymerase along the
DNA.
10.The amount of adenine=20 % in the DNA, therefore the amounts of T =20%, G =30% and
C =30%.
11.One half of the helical structure is lost is defined as the melting temperature (T m).
12.The loss of helical structure in DNA, called denaturation.
13.DNA that contains high concentrations of G and C denatures at high temperature. Why?
14.DNA polymerase uses a DNA as a templet for DNA replication.
15.RNA polymerase uses a DNA as a templet for synthesis RNA.
16.An origin of replication is a site that Allowing DNA replication to commence and (rich in
A=T). Why?
17.A eukaryotic chromosome has many origins of replication
18.A prokaryotic DNA has a single origin of replication.
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19.Replication of dsDNA is bidirectional.
20.DNA replication occurs in the S phase of the cell cycle.
21.Dna A protein initiates unwinding of DNA.
22.DNA helicases: require energy (ATP) for unwinding or separate the DNA.
23.Single-stranded DNA-binding (SSB) proteins has two functions,1. Keep the two strands of
DNA separated 2. Protect the DNA from nucleases that degrade ssDNA.
24.Type I DNA topoisomerases, cut one strand of the DNA duplex and relax negative
supercoiled DNA only.
25.Type II DNA topoisomerases, cut both strands of a DNA duplex, can relax either
negatively or positively supercoild DNA molecules.
26.DNA gyrase is a type II topoisomerase found in bacteria and plants that able to introduce
negative supercoils into circular DNA using ATP.
27.primase: A specific RNA polymerase (DnaG), is responsible for synthesis of RNA primer.
28.Primer is a short, single-stranded segment of DNA or RNA.
29.Synthesis direction of DNA nd RNA is form its own 5ˋ end to its 3ˋ end (5'→3„).
30.DNA polymerase III possess synthesis of DNA in 5'→3' direction using templet (ssDNA)
and a “proofreading” activity (3'→5' exonucleaseactivity) (remove DNA).
31.DNA polymerase III possess (5‟→3' Exonuclease and polymerase activities).
32.The leading strand is synthesized continuously, and the lagging strand discontinuously.
33.An okazaki fragment in lagging strand is made up of RNA primer and short fragment
DNA.
34.DNA polymerase I possess 1. synthesis of DNA in 5'→3' direction using templet (ssDNA)
and 2. (5'→3' exonuclease activity) and 3. (3'→5' Exonuclease activity) (Remove RNA).
35.DNA ligase required ATP for Joined (ligated) the fragment DNA.
36.DNA polymerase α contains primase (synthesis RNA primer) and DNA synthesis.
37.Telomeres are repetitive non coding DNA sequences plus protein at the end of linear
chromosomes. That is preventing attack by nucleases.
38.In eukaryote, a telomere is a region of RNA primers attach further on the DNA strand and
DNA polymerase comes along and continues to make a new DNA.
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39.Telomerase is unique because it contains an RNA molecule and protein that acts as a revers
transcriptase.
40. The function of Telomerase at the telomere it adds new DNA to the longer strand of the
telomere overhang.
41.Telomeres are shortened slightly after every round of replication or cell dividing.
42.Nucleoside analogs can be used to block DNA chain growth and they are useful in
anticancer and antiviral chemotherapy.
43.There are five classes of histone proteins. Two each of histones H2A, H2B, H3, H4 and
H1.
44.Nucleosome is composed of a little less than two turns of DNA wrapped around a set of
eight proteins called histones, which are known as a histone octamer. Each histone
octamer is composed of two copies each of the histone proteins (H2A, H2B, H3, and H4)2
45.Methyl-directed mismatch repair in E. Coli, the Mut proteins, S and L, recognize the
mismatch and identify the parental (methylated) strand, and Mut H cleaves the daughter
strand.
46.In bacteria, ultraviolet light can cause thymine dimers that are recognized and removed by
(UV-specific endonuclease) uvrABC.
47.In human, ultraviolet light can cause thymine dimers that are recognized and removed by
XP proteins.
48.Defects in the XP proteins cause xeroderma pigmentosum.
49.Types of RNA are mRNA, tRNA and rRNA.
50.RNA polymerase 1. Does not require a primer and 2. Does not appear to have proofreading
activity.
51.Termination: The elongation of the single-stranded RNA or mRNA depende on the protein
known as the ρ (rho) factor.
52.The termination site for transcription is recognized by ρ (rho) factor.
53.Rifampin inhibits the initiation of transcription by binding to the β subunit of prokaryotic
RNA polymerase.
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54. Actinomycin D, 1. It binds to the DNA template and interferes with the movement of
RNA polymerase along the DNA and 2. Intercalating into the narrow groove of the Ds
DNA.
55. In eukaryotic, Pre-mRNA or hn RNA undergoes modifications, 1. Addition poly-A tail at
3ˋ and 7-methylguanosine cap at 5ˋ at pre-mRNA 2. Splicing of pre-mRNA to remove noncoding introns and join exons.
56.The start codon (AUG) always codes for methionine in eukaryotes and a modified
Metionine (formyl-methionyl-tRNA; fMet) in prokaryotes.
57.Termination (“stop” or “nonsense”) codons are UAG, UGA, and UAA, do not code for
amino acids.
58.Silent mutation: The codon changed for the same amino acid, Missense mutation: The
codon changed for a different amino acid, Nonsense mutation: The codon changed to
become a termination codon.
59.Frame-shift mutations: if one or two nucleotides are either deleted from or added to the
coding region of a message sequence.
60.The function of Nonsense codons are termination of translation.
61.Amino acid is attached to tRNA at 3ˋ end.
62.tRNA has a covalently attached amino acid, it is said to be charged tRNA or aminoacyl
tRNA.
63.Aminoacyl-tRNA synthetases required ATP for attachment of amino acids to their
corresponding tRNAs.
64.Aminoacyl-tRNA synthetases have a “proofreading” or “editing” activity that can remove
amino acids from the tRNA molecule.
65.Ribosomes are consisting of 1. Large complexes of protein and 2. rRNA and They consist
of two subunits (one large and one small).
66.The prokaryotic (large subunit 50S) and (small subunit 30S) ribosomal subunits together
form a 70S ribosome.
67.The A site of rRNA is binds an incoming (tRNA charged with amino acid aminoacyltRNA.
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68.The P-site of rRNA is occupied by peptidyl-tRNA.
69.The E site of rRNA is occupied by the empty tRNA as it is about to exit the ribosome.
70.Wobble hypothesis explain how the tRNAs can recognize more than one codon for a
specific amino acid.
71.“Wobble” hypothesis Nontraditional base-pairing between the 5'-nucleotide (first
nucleotide) of the anticodon with the 3'-nucleotide (last nucleotide) of the codon (at
nucleotide number 3 of the codon).
72.The Shine-Dalgarno (SD) sequence is a ribosomal binding site in prokaryotic messenger
RNA helps to initiate protein synthesis by aligning the ribosome with the start codon.
73.In eukaryotes, the 40S ribosomal subunit binds close to the cap structure at the 5-end (7methylguanosine cap) of the mRNA and moves down the mRNA until it encounters the
initiator AUG. This “scanning” process requires ATP.
74.. Trimming Portions of the protein chain must be removed by specialized endoproteases,
resulting in the release of an active molecule.
75.POSTTRANSLATIONAL MODIFICATION OF POLYPEPTIDE CHAINS included
Phosphorylation
Glycosylation
Hydroxylation,
carboxylation,
biotinylated,
and
farnesylated protein.
76.Protein Folding can be spontaneous that required “molecular chaperons,” and adenosine
triphosphate hydrolysis.
77.Ubiquitin are responsible for destruction of misfolded or defective proteins.
78.Ubiquitinated proteins are degraded by a cytosolic complex known as the proteasome.
79.PCR is a method for amplifying a selected DNA sequence.
80.A. Steps of a polymerase chain reaction (PCR): 1. Primer costruction: Taq DNA
polymerase needs a primer to provide a 3-OH group for DNA synthesis. 2. Denature the
DNA: The DNA is heated to separate the double-stranded target DNA into single strands.
3. Annealing of primers to ssDNA: The separated strands are cooled and allowed to anneal
to the two primers (one for each strand). 4. Chain extension (extend the primer with taq
DNA polymerase): Taq DNA polymerase adds nucleotides to the 3'-hydroxyl end of the
primer.
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81. Thirty cycles of PCR can amplify DNA 230 fold.
82.The properties of Taq DNA polymerase is It is not denatured at the melting temperature of
DNA (95˚C).
83.The Applications of PCR are 1. Comparison of a normal cloned gene with a mutant form
of the gene. 2. Detection of low-abundance nucleic acid sequences 3. Forensic analysis of
DNA samples 4. Prenatal diagnosis and carrier detection of cystic fibrosis.
Q2: Write ‘true’ or ‘false’ and correct the error. (Difficult 2)
1. Nonsense codons have no function. (False), termination of translation.
2. There are more one codon for some amino acids. (True)
3. One codon encodes only one amino acid.
(True)
4. One tRNA can be charged only with one specific amino acid. (True)
5. The anticodon in the tRNA recognises the amino acid.
(False) bind with the codon in
the mRNA.
6. The inhibitors of prokaryotic translation can be used as antibiotic such as
streptomycin, tetracyclines, puromycin, chloramphenicol, and erythromycin. (True)
7. Diphtheria toxin inhibits EF2 and inhibits translation in eukaryotes by preventing
translocation. (True)
8. Streptomycin inhibits of translation in eukaryotes. (False) in prokaryotes
9. In eukaryotes, non-coding sequences in a gene are known as exon. (False) known as
intron.
Q3: Fill in the blank
1. Anticodons are presented on tRNA.
2. Nonsense codons have no complementary anticodons.
3. Introns are removed during splicing.
4. Methionyl tRNA initiates translation in eukaryote.
5. formylmethionyl tRNA initiates translation in prokaryote.
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6. Imprecise recognition of the third base of a codon by anticodon is known as wobble
hypothesis.
7. Binding of formylmethionyl tRNA to 30S subunit of ribosomes is inhibited by
streptomycin.
8. Chloramphenicol inhibits the peptidyltranferase activity of 50S ribosomal subunit.
9. A mutation resulting from substitution of one base by another is known as a point
mutation.
10. Frame-shift mutations occur due to insertion or deletion of bases.
11. RNA contain uracil, adenine, guanine, and cytocine.
12. Tetracycline prevents synthesis of polypeptide or elongation by Preventing binding of
aminoacyl tRNA to the A site.
13. Puromycin causes inhibition of elongation and premature chain termination in both
prokaryotes and eukaryotes.
14. Tetracycline bind irreversibly to 50S subunit so inhibit translocation and inhibit binding
of amino acyl tRNAs to
15. Reverse transcriptase activity is present in the eukaryotic in the Telomerase.
16. Ultraviolet light can cause thymine dimers.
17. In bacteria, uvrABC protein Repair of damage caused by ultraviolet (UV) light.
18. In human, XP protein Repair of damage caused by ultraviolet (UV) light.
19. DNA Repair of the missmatch in E-Coli by Mut proteins.
20. Methyl-directed mismatch repair in E. coli, the Mut proteins, S and L, recognize the
mismatch and identify the parental (methylated) strand, and Mut H cleaves the daughter
strand.
21. Thirty cycles of PCR can amplify DNA 230 fold.
22. In DNA replication, the removal of the RNA primers by DNA polymerase I.
23. Elongation and polymerization of lagging strand proceeds via generation of okazzki
fragments.
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