The document is a practice exam for a Molecular Biology course. It contains 33 multiple choice questions testing knowledge of DNA and RNA structure, DNA replication, transcription, translation, and gene cloning techniques. It also includes 3 essay questions asking students to describe aspects of DNA structure, the process of DNA replication, features of common cloning vectors (plasmids, cosmids, YACs), and the principles and applications of PCR or Sanger sequencing. The exam is designed to evaluate students' understanding of fundamental concepts in molecular biology.

1. M. Sc Batch (2) Final semester (1) Supplementary Examinations
Molecular Biology
Date : Wednesday 12.3.2008 Time allowed: 3 hours.
8:30 – 11:00 a.m.
Name: _____________________________________________________Index No.:_____________
SECTION ONE: One best answer
Encircle the letter that describes the best answer.
1. The chemical bonds holding the DNA double helix together are:-
a. hydrogen bonds
b. hydrophobic bonds
c. S-S bonds
d. ionic bonds
e. all of these
2. Which element is not present in DNA?
a. oxygen
b. nitrogen
c. carbon
d. sulfur
e. phosphorus
3. . Each nucleotide in a DNAmolecule is composed of:-
a. a nitrogenous base and a phosphate group
b. a sugar called ribose, a nitrogenous base, and a phosphate group
c. a sugar called deoxyribose, a nitrogenous base, and a phosphate group
d. a sugar called deoxyribose and a phosphate group
e. deoxyribose and a nitrogen base.
4.. The combination of DNA and histones is known as:-
a. chromatin
b. chromatid
c. chromosome
d. chromatosome
e. chloroplast
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2. 5. The gene is:-
a. Polymer of nucleosides joined by phosphodiester bond
b. DNA segment carrying information about a protein
c. Only made of introns
d. Only made of exons in eukaryotes
e. The same as chromosome
6. Which of the following is not needed for DNA replication?
a. ribosomes
b. DNA
c. Nucleotides
d. Enzymes
e. All of the above are needed
7. What is the function of the 3' to 5' exonuclease activity of DNA polymerases?
a. removes wrongly - inserted bases during replication
b. removes pyrimidine dimers
c .removes the RNA primers of Okazaki fragments
d. initiates mRNA synthesis
e. processes precursor mRNA
8 Codons are composed of:-
a. triplet sequences of nucleotide bases in mRNA
d. triplet sequences of nucleotide bases in DNA
c. triplet sequences of amino acids in polypeptide chains
d. triplet sequences of deoxyribose sugars in DNA
e. none of the above
9. RNA polymerase uses --------- as a template to synthesize -----
a. RNA, protein
b. RNA, DNA
c. DNA, RNA
d. DNA, protein
e. DNA, DNA
10. Ribosomes are constructed in the ___.
a. endoplasmic reticulum;
b. nucleoid;
c. nucleolus;
d. nuclear pore
e. non of the above
11. The process of translation requires the presence of:-
a. mRNA, tRNA and ribosomes
b. mRNA, ribosomes and RNA polymerase
c. DNA, mRNA and RNA polymerase
d. chromatin, DNA and amino acids
e. free nucleotide bases, amino acids and ribosomes
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3. 12. The portion of DNA which directs RNA polymerase to transcription start site is:-
a. Insert
b. Intron
c. Vector
d. Exon
e. Promoter
13. Concerning the 20 standard amino acids:-
a. each amino acid has three codons
b. some amino acids have no codons
c. one codon can code for more than one amino acid
d. one amino acid can not be coded for by more than one codon
e. one codon codes only for one amino acid
14. which of the following DNA sequences is complementary to the sequence CTAGAAC.
a. CTAGAAC
b. AGCTCCA
c. GATCTTG
d. TCGAGGT
e. GUTCTTG
15. The flow of genetic information is in the following order:-
a. translation  replication  transcription
b .replication  transcription translation
c. transcription  replication  translation
d. replication  translation transcription
e. transcription  translation  replication
16. There is degeneracy in the genetic code. This means that:-
a. DNA is unstable.
b. codons frequently change.
c. multiple codons can code for a single amino acid.
d .multiple amino acids are coded for by a single codon.
e. all the above is correct.
17. RFLP analysis can be used to distinguish between alleles based on differences in:-
a. restriction enzyme recognition sites between the alleles
b. The amount of DNA amplified from the alleles during PCR
c. the ability of the alleles to be replicated in bacterial cells
d. the proteins expressed from the alleles
e. the ability of nucleic acid probes to hybridize to the alleles
18. The polymerase chain reaction is used to make many:-
a. RNA copies from a DNA template
b. RNA copies from a RNA template
c. DNA copies from a DNA template
d. DNA copies from a RNA template
e. none of the above
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4. 19. Southern hybridisation is a technique that is used for:-
a. detecting specific proteins in biological materials
b. detecting specific genes in samples of DNA
c. measuring the density of a macromolecule
d. measuring the length of metaphase chromosomes
e. All of the above
20. Taq polymerase:-
a. nails DNA fragments together
b. is isolated from retroviruses
c. is a thermostable enzyme
d. only functions at low temperatures
e. will only synthesise DNA from RNA.
21. Transfection is:-
a. The uptake of a plasmid into a bacterium
b. The joining of two different DNA molecules
c. The expression of a gene into a bacterium
d. The isolation of plasmid from a bacterium
e. Key step in RT-PCR.
22. Plasmids are:-
a. are linear DNA molecules
b. are circular DNA duplexes
c. are present in all bacteria
d. found in yeast
e. can not replicate independently
23. A copy DNA (cDNA) library:-
a. contains a copy of every gene in a genome
b. is made from denatured DNA
c. represents only the transcribed portion of the genome
d. can only be made if the sequence of a gene is already known
e. contains books of DNA sequences
24. If you want to clone the largest DNA fragments possible, which vector element would you
use?
a. plasmid
b. bacteriophage lambda
c. YAC
d. cosmid
e. BAC
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5. 25. An enzyme found in retroviruses (like HIV) that can be used to prepare DNA fragments
from mRNA is called:-
a. reverse transcriptase
b. RNA polymerase
c. DNA polymerase
d. integrase
e. RNAse
26. After combining DNA fragments in a cloning experiment, ___ is used to covalently join the
DNA segments:-
a. Restriction endonuclease
b. DNA Ligase
c. Reverse transcriptase
d. DNA polymerase
e. Helicase
27. What are the typical characteristics of a cloning vector?
a. Bacterial cells cannot survive without it when grown under certain conditions.
b. It contains restriction sites that allow the insertion of foreign DNA segments.
c. It can replicate in bacterial cells.
d. Only B and C are correct.
e. A, B, and C are correct.
28. Which of the following statements is true about developing cDNA?
a. mature mRNA directs the formation of the DNA.
b. mature mRNA does not contain exons
c. DNA taken from the nucleus is used to produce the cDNA
d. Both a and b are true.
e. none of the above are true
29. The following statements are true regarding Southern blotting EXCEPT:-
a. It involves transfer of DNA from a gel onto nylon membrane
b. It involves transfer of double stranded DNA from a gel to nylon membrane
c. It is helpful in detection of certain strains of infectious agents
d. It is used for detection of a mutation in a given gene
e. It uses capillary diffusion for fragment transfer
30. A northern blot is used to separate and study:-
a. genomic DNA
b. cDNA
c. RNA
d. short polypeptides
e. proteins
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6. 31. The following are involved in radioactive end-labeling of DNA probes:-
a. Random hexamers
b. terminal transferase
c. P32
d. Reverse transcriptase
e. B and c.
32. In the Sanger method of DNA sequencing, 2', 3'-dideoxyadenosine (ddATP):-
a. Is used to radioactively label the DNA.
b. Blocks further DNA synthesis when it is incorporated into the newly synthesized DNA strand in
place of dATP.
c. Blocks DNA synthesis at random positions along a DNA strand.
d. Has no effect on DNA synthesis when it is incorporated.
e. None of the above
33. By using the "reference sequence" developed in the human genome project, individual
differences are now being detected using:-
a. NPs
b. PSNs
c. SNPs
d. snaps
e. PNAs
34. DNA microarrays have made a huge impact on genomic studies because they:-
a. can be used to eliminate the function of any gene in the genome.
b. can be used to introduce entire genomes into bacterial cells.
c. allow the expression of many or even all of the genes in the genome to be compared at once.
d. allow physical maps of the genome to be assembled in a very short time.
e. enhance the efficiency of restriction enzymes.
35. The following is employed in DNA sequencing:-
a. plasmids
b. bacteriophage lambda
c. dideoxynucleotide triphosphate (ddNTP)
d. reverse transcriptase
e. DNA ligase
36. FISH is:-
a. Fluorescent immunosystem hybridization
b. Fluorescent in Situ hybridization
c. Useful in detection of chromosomal abnormalities
d. Requires DNA polymerase
e. Both b and c are correct
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7. Section Two
Answer all questions in the provided answer book
Question One
1. What are the major aspects of DNA structure described by Watson and crick in 1953?
2. List four structural differences between DNA and RNA.
3. What is the role of each of the major RNA types (mRNA, tRNA and rRNA) in protein synthesis?
Question two
Give a brief account about the process of DNA replication. In your answer describe the major steps of
the process and the exact role of each of the various enzymes and protein factors involved.
Question 3.
a. What are the features of each of the following cloning vectors?
(i) Plasmids. (ii) Cosmids. (iii) Yeast Artificial chromosomes.
b. Describe briefly the general procedure for gene cloning.
Question Four:
Give a brief account about the principle and application of one of the following techniques:
(i). Polymerase chain reaction
(ii). Sanger method for DNA sequencing
Good Luck!
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