This document contains a 40 question exam on molecular biology and genetics. The exam covers topics such as DNA structure and replication, gene expression and regulation, genetic engineering techniques including PCR, DNA sequencing, and genomics. It consists of two sections - the first contains 35 multiple choice questions and the second contains 4 short answer questions related to PCR and DNA sequencing techniques.

1. The Academy of Medical Sciences &
Technology
Faculty of Medical Laboratory Sciences
Batch (1 )M.Sc. Programme
Final semester (1) supplementary Examinations
Molecular Biology
Date: Tuesday 20.2.2007 Time allowed: 3 hours.
9:00 – 12:00 noon
SECTION ONE: One best answer
Encircle the letter that describes the best answer.
1. 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
2. Denaturing of double stranded DNA involves
a. Breakage into short double stranded DNA
b. Separation into two single strands
c. Removal of a phosphate group
d. Breakage of phosphodiester bonds
e. Removal of the non coding regions
3. The combination of DNA and histones is known as:
a. chromatin
b. chromatid
c. chromosome
d. chromatosome
e. chloroplast
4. DNA replication is described as semi-conservative because:
a. half of the DNA is replicated in each cell cycle.
b. each new DNA molecule contains half of the original molecule.
c. half of the DNA molecule is destroyed during replication.
d. DNA replication occurs on the right side of the cell in about half of all cell
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2. divisions.
e. There is no good reason to call it that. That is just its name.
5. 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
6. What is the function of the enzyme DNA polymerase?
a. To build a strand of DNA using DNA as a template.
b. To build a strand of DNA using a polypeptide as a template
c. To build a strand of mRNA using DNA as a template
d. To build a polypeptide using mRNA as a template.
e. To build a strand of DNA using mRNA as a template
7. Which of the following could be a probable recognition site for a restriction
enzyme:
a. 5`- CTGCAG-3`
b. 5`- CTAGAC –3`
c. 5` - GCCTGC-3`
d. 5`-CCACGG-3`
e. 5`- CAGCAG-3`
8. Which of the following statements is false regarding agarose electrophoresis?
a. DNA migrates towards the negative electrodes
b. large molecules migrate more slowly than small molecules
c. ethidium bromide is used to visualize the DNA
d. bromophenol blue is indicative of the distance migrated by DNA
e. ultra violet light is needed
9.Which of the following tools of recombinant DNA technology is INCORRECTLY
paired with its use?
a. restriction endonucleases production of DNA fragments for gene cloning
b. DNA ligase - enzyme that cuts DNA, creating sticky ends.
c. DNA polymerase - copies DNA sequences in the polymerase chain reaction
d. reverse transcriptase - production of cDNA from mRNA
e. electrophoresis – analysis of PCR products
10. The most common form of gene expression regulation in both bacteria and
eukaryotes is
a. translational control
b. transcriptional control
c. post-transcriptional control
d. post-translational control
e. control of passage from the nucleus
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3. 11. Which of the following is not part of the lac operon?
a. activator protein
b. operator
c. promoter
d. structural genes
e. repressor
12. Proteins that block the passage of RNA polymerase are called:
a. operons
b. activators
c. repressors
d. enhancers
e. promoters
13. Spontaneous mutations:
a. are caused by chemicals such as acridines and nitrous acid
b. are caused by physical agents such as ultraviolet light or x-rays
c. are the result of errors in the base pairing of nucleotides during replication
d. occur at a rate higher than the rate of induced mutations
e. all a, b, c and are correct.
14. In haemoglobin S the mutation in the beta chain results from:
a. insertion of a nucleotide
b. replacement of alanine by serine at codon # 6
c. deletion of a nucleotide
d. replacement of glutamate by valine at codon # 6.
e. either a or c
15. The following is a transversion;
a. Substitution of A to C
b. Substitution of A to G
c. Substitution of C to T
d. a and b are correct
e. None of the above is correct
16. Gene library" is a term used to describe:
a .a computerized listing of known DNA sequences
b. bacteria with plasmids containing DNA fragments representing the majority of
the genetic information from a plant or animal.
c. a collection of books about recombinant DNA technology.
d. a compilation of the amino acid sequences of protein coding genes
e. non of the above
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4. 17. Recognition sites of restriction enzymes:
a. are on double stranded DNA
b. can be 4-8 bp long
c. provide blunt and sticky ends
d. are usually palindrome sequences
e. all of the above (a-d) is correct.
18.VNTRs:
a. are good markers in forensic medicine
b. stands for variable numbers of tri repeats.
c. are commonly used for screening of infectious agents.
d. are key tools in gene cloning
e. all a-d are correct
19. Viruses naturally containing the enzyme reverse transcriptase are called:
a. riboviruses
b. immunoviruses
c. bacteriophages
d. rotaviruses
e. retroviruses
20. In the dideoxy sequencing method the use of dideoxy adenosine triphosphate
stops nucleotide polymerization
a. opposite A´s in the template strand
b. opposite T´s in the template strand
c. opposite G´s in the template strand
d. opposite C´s in the template strand
e. opposite any base selected randomly in the template strand
21. The information carried by a DNA molecule is in
a. its amino acid sequence
b. the sugars and phosphates forming its backbone
c. the order of the nucleotides in the molecule
d. the total number of nucleotides it contains.
e. the RNA units that make up the molecule
22. RFLP stands for
a. restriction fragment length position
b. restriction fragment length polyploidy
c. restriction fragment length phenotype
d. restriction fragment length polymorphism
e. restitution figment loose polymorphism
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5. 23. The polymerase chain reaction (PCR)
a. uses flanking primers
b. uses restriction enzymes
c. uses varying temperatures
d. all of the above
e. a and c
24. For a genetic disease, point mutations are usually first found by:
a. DNA hybridization
b. DNA sequencing
c. DNA cloning
d. Southern Blot
e. PCR
25. Cutting genomic DNA with a single restriction enzyme will result in DNA
fragments that:
a. are all of the same length
b. all end with the same base sequence pattern
c. all migrate the same distance on a gel
d. all have the same molecular weight
e. all contain the same genes
26. A northern blot is used to separate and study
a. genomic DNA
b. cDNA
c. RNA
d. short polypeptides
e. proteins
27. 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.
28. RNA may be converted to its complementary DNA by the enzyme:
a. RNA polymerase.
b. DNA polymerase.
c. Reverse transcriptase.
d. Topoisomerase
e. all of the above enzymes.
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6. 29. The following techniques are used to immobilize the corresponding
biomolecules:
a. Southern blotting for DNA
b. Northern blotting for proteins
c. Southern blotting for DNA and RNA
d. Dot-blot for RNA
e. Western blotting for DNA
30. A DNA copy of an mRNA molecule is called:
a single-stranded DNA
b. double-stranded DNA
c. rDNA
d. cDNA
e. Inverted DNA
31. In DNA hybridization the oligonucleotide complementary to target sequence is
called:
a. vector
b. antibody
c. plasmid
d. probe
e. primer
32. The following is correct about DNA sequencing
a. Sanger’s method involves base specific cleavage
b. The chemical method uses ddNTPs
c. Sanger`s method is performed only on single stranded DNA
d. DNA sequence is read on an agarose gel
e. The Maxam-Gilbert method is currently the method of choice
33. The following are involved in radioactive end-labeling of DNA probes:
a. alkaline phospahates
b. terminal transferase
c. P32
d. Reverse transcriptase
e. D is the only wrong answer.
34. The genetic makeup of an organism is its:
a. Phenotype
b. Prototype
c. Phenocopy
d. Genotype
e. Haplotype
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7. 35. The final complete sequence of human genome was finished in the year:
a. 1990
b. 1993
c. 1995
d. 2003
e. 2005
36. With the completion of the human genome project, the next frontier is
a. Nucleonics
b. Proteomics
c. Cytomics
d. Agronomics
e. all of the above
37. To identify an individual by DNA analysis of their blood, investigators look for
a. primers
b. DNA fingerprint
c. Probes
d. Nucleosomes
e. Transgenic fragments
38. Bacterial DNA is not cleaved by their own restriction enzymes because bacteria
add _______________ to their own DNA
a. nucleotides
b. peptides
c. methyl groups
d. resistant plasmids
e. phosphate groups
39. In genetic engineering, DNA ligase is used as:
a. a probe
b. a sealing enzyme
c. a restriction enzyme
d. a mutagen
e. non of the above
40. 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 introns
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
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8. SECTION TWO
Answer all questions in the answer book provided.
Question 1: A question on PCR
Suppose you want to use PCR (polymerase chain reaction) to amplify the following
sequence:
5’-ACG GGC ACG GAT CCC CCG GCA TAA GGC TTT ATA ATA TGC GAT
AGGCGC TGG TCA GAT CCT GGA TAT GGC GGA CAT TAT AAT AAA CAA
CCCGCG CCG GCC CGG-3’
A.There are three steps in each cycle of PCR, list them sequentially (in the order in which
they are performed) explaining what happened in each step.
B. Write the sequence of the two 18-residues primers that could be used to amplify the
sequence (label 5’ and 3’ ends of each primer clearly).
C. What components do you need to set up your PCR reaction in addition to the template
DNA and primers?
D. If the PCR amplification was 100% efficient how many copies of DNA would you get
after 30 cycles?
Question 2: A question on DNA sequencing
A. List 3 of the specific chemicals used in the chemical degradation method (Maxam-
Gilbert), indicating their role in the process.
B. What are dideoxyribonucleotides? Why are they necessary in the Sanger method of
DNA sequencing?
2. The figure below shows an autoradiogram of a dideoxynucleotide sequencing gel.
Write down the sequence of the sample DNA.
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9. +
Question 3: A question on gene cloning:
A. What are plasmids? List three of the properties that make them excellent cloning
vectors.
B. Briefly outline the general procedure of gene cloning.
C. Define the term ``DNA library``. What is the difference between genomic DNA
library and cDNA library? What are the advantages of obtaining cDNA library?
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10. Good Luck!
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