15 Genetic Engineering

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                        Chapter 15. Genetic Engineering

        All fundamental life processes are regulated by genes. A variety of very sensitive techniques can
be applied for isolation and characterization of genes and for quantitation of gene products. Manipulation
of DNA to change its structure is called “biotechnology” or “genetic engineering”. Allaby (1995) defined
the genetic engineering as the modification of the genetic information of living organisms by direct
manipulation of their DNA. It is a key element in cloning and can also be used to study the function of
certain fragment of DNA. The DNA molecule is broken at desired places to isolate a specific DNA
segment and then insert it in another DNA molecule at a desired position. The product so formed is
known as recombinant DNA. With the technique of genetic engineering, we can isolate and clone single
copy of a gene or a DNA segment in an indefinite number of copies, all identical. This becomes possible
because bacteria, phages and plasmids reproduce in their usual manner even after insertion of foreign
DNA, so that the inserted DNA also replicates faithfully with the parent DNA. This technique is called
gene cloning. More recently, polymerase chain reaction (PCR) involving a thermostable DNA
polymerase enzyme (e.g. Taq DNA polymerase, isolated from algae, Thermus aquaticus) has also been
used to obtain millions of copies of DNA segments of our choice.

RECOMBINANT DNA TECHNOLOGY

         Recombinant DNA technology means combining two different organisms to generate a
recombinant DNA. This involves manipulation of the two DNAs involved and as such the technique is
called as genetic engineering. This technology is used in the cloning of specific genes, which may be
either isolated from the genome or synthesized in form of cDNA from mRNA. The cloning of DNA is
possible due to the presence of another DNA molecule, which is capable of replication. This other DNA
molecule is called as vector which could be a plasmid or bacteriophage.

Restriction Enzymes. The primary requirement in Recombinant DNA technology is the frequent use of
restriction enzymes, which are
endonucleases, cutting the DNA
double helix at specific sites into
fragments containing “gene of
interest”. They have the capacity
to recognize specific base
sequences on DNA and then to
cut each strand at a specific place.
They restrict the infection of virus
on bacteria by destroying the viral
DNA that had entered in the
bacterial cell, without affecting
the bacterial DNA, thus they are
named as restriction enzymes.
Each bacterium has its own
restriction enzyme and each
enzyme recognizes only one type
of unique sequence. This allow
dividing a long DNA molecule
into fragments that can be
separated from each other by size     Fig. 15.1. Formation of recombinant DNA by using restriction
using gel electrophoresis. Thus,                         enzyme and DNA ligase.
these enzymes proved a good tool
for cutting DNA at specific sites, as we can employ them for cleaving the DNA at specific sites at our
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will. Restriction enzymes are named after the bacterium from which they are isolated. e.g., EcoRI is
isolated from Escherichia coli, and BamHI is isolated from Bacillus amyloliquefaciens.


Plasmids.         Plasmids      are
autonomous elements, whose
genome exist in the cell as extra-
chromosomal units. They are self-
replicating circular duplex DNA
molecules in the bacterium and
replicates independently from the
bacterial DNA. In recombinant
DNA technology, circular plasmid
DNA can be cleaved at one site
with the help of restriction
enzyme to give a linear DNA
molecule. A foreign DNA
segment can now be inserted by
joining the ends of broken circular
DNA to the two ends of foreign
DNA, thus again creating a
circular DNA molecule, and now
the product is known as
recombinant DNA. The plasmid
DNA carrying the foreign DNA
fragment is then put back into a
suitable bacterium and then the
bacterium is allowed to grow in
large quantities. The plasmid
DNA will also replicate alongwith
the bacterial DNA producing
multiple copies. It can be isolated
at the end and the inserted DNA           Fig. 15.2. Use of plasmid to obtain multiple copies of
or “gene of interest” can be                                 recombinant DNA.
obtained in multiple copies by the
of restriction enzymes. Thus large number of foreign genes can be produced by this technology.

Phages. Viruses, particularly bacteriophages provide another source of cloning vectors. Usually a phage
is a linear DNA molecule, a single break will generate two fragments, which are joined together with the
foreign DNA to generate a recombinant DNA. Multiple copies of recombinant DNA can be made and the
foreign DNA can be isolated in large quantities. The only limitation of using phage as a vector is that, the
size of the foreign DNA must not be too long because it has to be accumulated in the phage head. Using
these techniques, we can isolate and clone single copy of a gene or a DNA segment into an indefinite
number of copies, all identical. This phenomenon is called as gene cloning.

Gene Library. By using the technique of gene cloning, genomic DNA is extracted, broken into
fragments of reasonable size by restriction endonucleases and the fragments are then inserted into a
cloning vector (such as plasmids or bacteriophages) to generate a population of cloned DNA fragments. A
set of fragments cloned in this manner is called gene library or gene bank. Gene libraries are of two
types- (i) Genomic library, which represents both introns and exons and is prepared from the total DNA
of a cell or tissue in the form of random and unidentified clones. The cloned DNAs are produced by
isolation of DNA fragments to be cloned and inserting them into a suitable vector to obtain multiple
copies of clones. The next step is the selection of the desired clones and use of these clones for the
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construction of genomic library. (ii) cDNA library, which represents only exons. First, the cDNA is
prepared from mRNA using reverse transcriptase and this cDNA is then inserted into a vector to obtain
multiple copies. Since, mRNA do not consists of exons only, therefore cDNA library have exons only.
From gene library, a particular gene of interest can be isolated at any time, grown in large quantities and
used wherever required.

Molecular Probes. These are small segments of nucleic acids, either radioactive labeled or non-
radioactive labeled, with a sequence complementary to at least one part of the desired DNA. These probes
are prepared for commercial purposes and are believed to be the most sophisticated and sensitive means
to identify genes or specific DNA sequences. The most commonly used DNA probe is made up of tandem
repeats of GATA. DNA/RNA probes have been commercially used for diagnosis of infectious diseases,
identification of food contamination, isolation of genes, variety of microbiological tests and in forensic
tests, e.g.: DNA fingerprinting.

TECHNIQUES USED IN BIOTECHNLOGY

         For better understanding of molecular genetics and utilize our knowledge to the best level,
various instruments were developed to be used in biotechnology. One of them is electrophoresis, which
involves separation of molecules according to their shapes, net charges and molecular weights in an
electric field, usually on solid or semi-solid support media. Polyacrylamide gels are used for DNA
sequencing; agarose gel is used to isolate DNA segments; acrylamide gels are used for analyzing the size
and charge of proteins.
         X-ray diffraction technique is used to analyze the three dimensional structure of DNA, RNA
and proteins. The analytical ultracentrifuge is mainly used for isolating organelles like nucleoli,
ribosomes, mitochondria and chloroplast. The method employs the use of sedimentation rate of a
substance during ultracentrifugation according to its density and shape.
         Another technique, the chromatography employs separation of molecules by difference in their
solubilities in organic solvents, molecular weight and specific binding properties for the support medium.
This method was used by Chargaff to determine the composition of bases in DNA. His findings helped
Watson and Crick in proposing the double helical model of DNA.
         Biotechnology involves manipulation of the normally existing DNA sequences. For this purpose
DNA molecules have to be separated, rejoined, synthesized or broken down. If DNA is treated with an
alkali (0.2 N NaOH) it gets separated into two single strands. This is called as denaturation. Double
stranded DNA can be made single stranded by boiling also; this method of denaturation is known as
melting. Since G and C base pairing involves three hydrogen bonds as compared to two hydrogen bonds
in A-T base pairing, the higher the G-C content the higher the melting temperature.
         In case of melting, the DNA is boiled and then cooled quickly, so the strands remain single.
However, if they are cooled slowly, the complementary strands will pair and reform double stranded
DNA again. This process is called as renaturation or annealing of DNA.

TYPES OF BLOTTING

Southern Blotting. This technique was developed by E.M.Southern (1975). In this technique a DNA
molecule is cut into discrete fragments by a restriction enzyme. Electrophoresis is then performed through
agarose gel for separating the various fragments according to size. The DNA is then made single stranded
by alkali treatment (NaOH). This gel is now placed below nitrocellulose filter, so that DNA from the gel
comes out onto the filter. The filter containing the DNA is dried and exposed to P32 labelled mRNA. The
radioactive mRNA will hybridize only with its complementary DNA fragment. The procedure, thus allow
specific identification of DNA sequence which are specific to RNA molecules.

Northern Blotting. This technique was developed by Alwine (1979). In this technique, RNA is used
instead of DNA and amino-benzyloxymethyl paper is used in place of nitrocellulose filter, however
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                            Fig. 15.3. Steps involved in Southern blotting.

nitrocellulose filter can also be used. This technique is just opposite to southern blotting. Here RNA is
fixed and exposed to radioactive DNA for identification.

Western Blotting. This technique was developed by Towbin (1979) to find out the newly specific
proteins encoded by a transformed cell. The extracted proteins are subjected to Polyacrylamide gel
electrophoresis (PAGE) and are then transferred onto nitrocellulose filter. Nitrocellulose is then used for
probing with a specific radioactive labelled antibody (normally with I125) and the signal can be detected
by autoradiography.

EUGENICS, EUTHENICS, EUPHENICS

        The term eugenics was coined by Francis Galton (1885). It deals with the application of the laws
of genetics for the improvement of human race. It aims for the betterment of already existing individuals
by selecting better individuals and rejecting defective individuals, so that the germplasm of better
individuals would be preserved and inherited in the future generation, thereby improving the human race.
Eugenics can be applied in two ways- (i) by encouraging marriage between desired individuals having
better germplasm to assure its continuity, called as positive eugenics. (ii) by discouraging marriage
between defective individuals that may have various sex linked diseases, called as negative eugenics.
        Another method involves betterment of human race by improving their environmental conditions,
such as better nutrition, education and medical facilities, called as euthenics.
        Human race can also be improved by the treatment of inherited genetic diseases, especially
inborn errors of metabolism in which the missing or defective enzyme has been identified. This method is
called as euphenics. Although it has proved to be very useful, yet it has few limitations- (i) only a small
fraction of inherited diseases can be cured because geneticists could not identify the errors of many
genetic diseases. (ii) the genetically treated individual will have to encounter the forces of natural
selection.
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APPLICATIONS OF BIOTECHNOLOGY

In Medicine. Drugs can be manufactured for the treatment of diseases by using biotechnology. Such
drugs can be manufactured in bacterial cell in large quantities, if the corresponding genes for human can
be cloned in phages or bacteria. It also makes the production of the drug very cheap. Two such drugs are
insulin for the treatment of diabetes, and interferons for the treatment against tumor viruses. Synthetic
human growth hormone has been also made and being sold under commercial name prototropin (USA)
and somatonorm (Britain), under license from Genetech Inc., USA. Vaccines are also being made using
biotechnology which are 100% efficient with no risk of contamination. At present there are vaccines for
Rabies virus, Hepatitis B virus, Vibrio cholerae, Plasmodium falciparum, etc. Biotechnology also offers a
rational approach for understanding the molecular basis of many diseases like sickle cell anaemia,
thalassemia, cystic fibrosis, etc.

In Industries. Through recombinant DNA technology, variety of genes can be cloned in vectors
(plasmids or phages), which then can be utilized for the synthesis of gene products. These genes can be
used for the synthesis of variety of other chemical compounds including antibiotics, enzymes and other
organic compounds. Enzymes produced by this technology reduces the cost of fermentation in many
industries and pharmacy, thereby reducing the cost of the product. Various organic compounds can also
be synthesized with reduced cost. e.g., glucose, ethyl alcohol, butanol, acetic acid, acetone, etc.

In Agriculture. Biotechnology can also be utilized for the improvement of crops. Genes can be
manipulated through recombinant DNA technology and cloning, to make the plants resistant to various
diseases and for improving their production. This would increase the nutritive value of plant and animal
food. Manipulation of genes to make the plant fix nitrogen directly from the atmosphere, rather than from
fertilizers would reduce the cost of the plant product.


                                  COMPETITION DESK # 15

1. Which of the following is related to genetic
   engineering?                                         5. Known sequence of DNA that is used to find
   (a) Plasmid        (b) Heterosis                        complementary DNA strand is
   (c) Plastid        (d) Mutation                         (a) vector        (b) DNA probe
                                                           (c) Plasmid       (d) recombinant DNA
2. The name of Tenim and Baltimore is
   associated with                                      6. RNA retroviruses have a special enzyme
   (a) Photorespiration                                    that
   (b) Reverse transcriptase                               (a) disintegrates host DNA
   (c) RNA synthesis                                       (b) polymerizes host DNA
   (d) All of these                                        (c) transcribes viral RNA to cDNA
                                                           (d) translates host DNA
3. The restriction endonuclease is used for
   cutting                                              7. Each restriction enzyme cleaves a molecule
   (a) mRNA           (b) ssDNA                            at
   (c) RNA fragment (d) dsDNA                              (a) methyl groups
                                                           (b) the ends of genes
4. Plasmids are                                            (c) the time of DNA replication
   (a) New type microorganisms                             (d) a particular nucleotide sequence
   (b) A type of nucleoid
   (c) Linear chromosomes                               8. In recombinant DNA technology a plasmid
   (d) Extra chromosomal circular genetic                  vector must be cleaved by
   material
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    (a) the same enzyme that cleaves the donor       16. Which one of the following is incorrect
    gene                                                 regarding plasmids
    (b) modified DNA ligase                              (a) these are extra-chromosomal materials
    (c) a heated alkaline solution                       found in bacterial cells.
    (d) four separate enzymes                            (b) mostly they can be transmitted from cell
                                                         to cell by infection without bringing about
9. One of the following is not a step involved           the death of the host cells.
   in recombinant DNA technology                         (c) they can be integrated into the host
   (a) cuts made in a DNA molecule with the              chromosomes.
   help of restriction enzymes                           (d) they are integral but inert part of the
   (b) joining of DNA fragments with the                 genetic element.
   vector
   (c) cloning of hybrid DNA into the host           17. The phage ghost represents the
   (d) karyotyping of the host DNA                       (a) virion protein coat
                                                         (b) virion nucleic acid
10. Which of the following is a desirable                (c) lysogenic viral particle
    characteristic for a cloning vector?                 (d) lytic viral particle
    (a) a replication site
    (b) restriction endonuclease sites               18. Assertion (A): The bacterial genome is
    (c) drug resistant genes                             highly folded.
    (d) all of these                                     Reason (R): Bacterial genome lacks histone
                                                         proteins.
11. Consider the following statements about              (a) both A and R are correct and R is a
    retrovirus (i) it has an enzyme located in its       correct explanation of A.
    coat (ii) in it, the newly formed DNA                (b) both A and R are correct but R is not a
    becomes a part of the host cell chromosome           correct explanation of A.
    (iii) it has double stranded DNA (iv) some           (c) A is true and R is false.
    of them are oncogenic. Of these, the correct         (d) both A and R are false.
    statements are
    (a) ii, iii and iv     (b) i, iii and iv         19. Assertion (A): Plasmids are extra-
    (c) i, ii and iv       (d) i, ii and iii             chromosomal DNA.
                                                         Reason (R): Plasmids are found in all
12. Plasmids that can integrate in the bacterial         eukaryotic cells.
    DNA are called                                       (a) both A and R are correct and R is a
    (a) chromosomes (b) oxysomes                         correct explanation of A.
    (c) mesosomes      (d) episomes                      (b) both A and R are correct but R is not a
                                                         correct explanation of A.
13. Bacteriophage is large used by geneticists           (c) A is true and R is false.
    because these                                        (d) both A and R are false.
    (a) contain DNA (b) kill bacteria
    (c) are small      (d)perform transduction       20. DNA-RNA hybrids are made by using the
                                                         enzyme
14. Viral vaccines contain                               (a) reverse transcriptase
    (a) live viruses                                     (b) DNA polymerase
    (b) live attenuated viruses                          (c) RNA polymerase
    (c) extracts of pathogenic viruses                   (d) DNA hybridase
    (d) all of these
                                                     21. Biological scissors are common name of
15. Largest animal virus is                              (a) enzymes
    (a) pox virus                                        (b) restriction endonucleases
    (b) penicillium virus                                (c) restriction exonucleases
    (c) wound tumor virus                                (d) restriction DNAse
    (d) coliphage
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22. When the number of genes increases in
    response to a signal, it is called as          31. Labelling of nucleic acid is
    (a) gene dosage                                    (a) DNA probing (b) DNA fingerprinting
    (b) gene pool                                      (c) nick translation (d) none of these
    (c) gene amplification
    (d) gene frequency                             32. Nitrogen fixing genes are called
                                                       (a) cos genes       (b) plasmid genes
23. First transgenic mouse grew twice the              (c) leg genes       (d) nif genes
    normal size after drinking water containing
    (a) copper           (b) iron                  33. Type I restriction enzyme
    (c) zinc             (d) radium                    (a) recognizes and cleaves DNA at specific
                                                       sequence.
24. When a segment of DNA is broken and then           (b) does not recognizes and cleaves the
    inserted into another DNA, it is called            DNA at specific sequence.
    (a) splicing         (b) cloning                   (c) recognizes specific sequence but cleaves
    (c) typing           (d) fingerprinting            DNA at non-specific sequence.
                                                       (d) recognizes and cleaves DNA at non-
25. The ability to change the sequence of amino        specific sequence.
    acids by altering the sequence of its cDNA
    is known as                                    34. Type II restriction enzyme
    (a) genetic engineering                            (a) recognizes and cleaves DNA at specific
    (b) protein engineering                            sequence.
    (c) polymerase chain reaction                      (b) does not recognizes and cleaves the
    (d) ligase chain reaction                          DNA at specific sequence.
                                                       (c) recognizes specific sequence but cleaves
26. In recombinant DNA technology, the                 DNA at non-specific sequence.
    foreign DNA is inserted into another DNA           (d) recognizes and cleaves DNA at non-
    molecule known as                                  specific sequence.
    (a) DNA vector     (b) RNA vector
    (c) protein vector (d) cloning vector          35. In DNA mapping, the sequence tagged sites
                                                       are also known as
27. In cloning of Dolly sheep, the fusion was          (a) gene probes
    done between                                       (b) molecular markers
    (a) enucleated egg cell and udder cell             (c) DNA sequencers
    (b) egg cell and enucleated udder cell             (d) DNA analysers
    (c) egg cell and somatic udder cell
    (d) sperm cell and somatic cell                36. The principal enzyme used in genetic
                                                       engineering is
28. The universal DNA probe is made up of              (a) restriction endonuclease
    repeated tandem repeats of                         (b) restriction exonuclease
    (a) TATA           (b) GATA                        (c) ligase
    (c) CACA           (d) ATGA                        (d) all of the above

29. In which of the following, DNA fingerprints    37. Plasmid DNA is
    will be the same                                   (a) ds circular    (b) ss circular
    (a) siblings         (b) offspring                 (c) ds linear      (d) ss linear
    (c) identical twins (d) fraternal twins
                                                   38. Who was the first scientist to synthesize
30. Proteins are separated in polyacrylamide gel       DNA in vitro
    by                                                 (a) A. Garrod    (b) A. Kornberg
    (a) Southern blotting                              (c) J.D. Watson  (d) H.G. Khorana
    (b) Northern blotting
    (c) Western blotting                           39. cDNA is
    (d) Eastern blotting                               (a) copy DNA       (b)complementry DNA
                                                                                                    8

    (c) coupled DNA      (d) compound DNA               regarding antibiotics ?
                                                        (a) the term was given by Waksman in 1942
40. PCR stands for                                      (b) they are produced by micro-organisms
    (a) Polymerase Cyclic Reaction                      (c) some persons have allergy from them
    (b) Polymerase Chain Reaction                       (d) they are capable of curing any disease
    (c) Polyethyl Cytosine Reaction
    (d) Polymerisation Chain Reaction               48. Restriction enzyme was discovered by
                                                        (a) Waksman
41. Which of the following enzyme is used in            (b) Alexander Flemming
    PCR ?                                               (c) Berg
    (a) Gyrase        (b) Taq polymerase                (d) Werner, Smith, Nathans
    (c) Transcriptase (d) Hexokinase
                                                    49. Biosensors are
42. Which of the following is widely used in            (a) enzymes used in the industries
    genetic engineering                                 (b) analytic devices used to monitor the
    (a) Nitrosomonas and Klebsiella                     product of biological process
    (b) Escherichia and Agrobacterium                   (c) used to detect abnormal toxins in the
    (c) Nitrobacter and Azotobacter                     body
    (d) Rhizobium and Diplococcus                       (d) both b and c

43. The enzyme used in polymerase chain             50. DNA fingerprinting involves
    reaction is                                         (a) terminators    (b) VNTR loci
    (a) restriction enzyme                              (c) RFLPs          (d) cDNA
    (b) reverse transcriptase
    (c) DNA ligase                                  51. Which of the following is specially used in
    (d) DNA polymerase                                  genetic engineering (AFMC 2004)
                                                        (a) ligase          (b) gyrase
44. Super bug denotes to                                (c) endonuclease (d) DNA polymerase
    (a) transgenic insect (b) virus
    (c) bacteria          (d) protozoa              52. Removal and insertion of gene is (AFMC
                                                        2002)
45. Assertion (A): Flavor Savr is the genetically       (a) Genetic engineering
    engineered variety of tomato.                       (b) Biotechnology
    Reason (R): Plasmids are related to genetic         (c) Cytogenetics
    engineering.                                        (d) Gene therapy
    (a) both A and R are correct and R is a
    correct explanation of A.                       53. Which of the following sequence is found in
    (b) both A and R are correct but R is not a         Rous-sarcoma virus? (AFMC 2000)
    correct explanation of A.                           (a) DNA→DNA→Proteins
    (c) A is true and R is false.                       (b) RNA→DNA→RNA→Protein
    (d) A is false and R is true.                       (c) RNA→RNA→Protein
                                                        (d) DNA→RNA→Protein
46. Assertion (A): Bacteria add methyl group to
    prevent degradation of their DNA.               54. Restriction endonuclease performs (AMU
    Reason (R): Restriction enzymes cut up              2002)
    DNA.                                                (a) DNA repair    (b) DNA replication
    (a) both A and R are correct and R is a             (c) DNA cleavage (d) All of these
    correct explanation of A.
    (b) both A and R are correct but R is not a     55. Clones are (AMU 2003)
    correct explanation of A.                           (a) Dolly sheep
    (c) A is true and R is false.                       (b) Monozygotic twins
    (d) A is false and R is true.                       (c) Bacterial colony from a single strain
                                                        (d) All of the above
47. Which of the following is the false statement
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56. Human Genome Project is being headed by             (b) RNA synthesis
    (AMU 2002)                                          (c) reverse transcription
    (a) Watson      (b) Crick                           (d) all of these
    (c) Bateson     (d) Morgan
                                                     66. Viroids differs from viruses in being (BHU
57. A total number of nitrogenous bases in               1994)
    human genome is estimated to be about                (a) naked RNA molecules only
    (AIIMS 2004)                                         (b) naked DNA molecules
    (a) 3.5 million (b) 35000                            (c) naked DNA packaged with viral genome
    (c) 35 million  (d) 3.1 billion                      (d) satellite RNA packaged with viral
                                                         genome
58. Which sensitive technique is used for the
    diagnosis of AIDS (AMU 2004)                     67. The proteins which can inhibit viral
    (a) ELISA          (b) Southern blot                 reproduction is (HRPMT 1995)
    (c) Northern blot (d) Immuno diffusion               (a) interferon     (b) antigen
                                                         (c) lesion         (d) all of these
59. The technique which involves addition or
    deletion of genes is (AFMC 2002)                 68. Genetic       counselors   can    identify
    (a) Gene therapy (b) Genetic engineering             heterozygous individuals by (BHU 2004)
    (c) Gene splicing (d) Artificial synthesis           (a) height of individuals.
                                                         (b) colour of individuals.
60. Mule is a product of (AFMC 2004)                     (c)screening procedures.
    (a) breeding experiments in laboratory               (d) all of these.
    (b) induced mutation
    (c) hybridization                                69. Which of the following animal is mostly
    (d) interspecific hybridization                      used in genetics experiment ? (CPMT 2003)
                                                         (a) Butterfly       (b) Dragonfly
61. Viral genome, incorporated and integrated            (c) Housefly        (d) Fruifly
    with bacterial genome is referred to as
    (AFMC 2005)                                      70. India’s wheat revolution in the 1960s was
    (a) RNA           (b) prophages                      possible primarily due to (CBSE 2004)
    (c) DNA           (d) both b and c                   (a) hybrid seeds
                                                         (b) increased chlorophyll content
62. Sexual reproduction in which DNA of                  (c) mutation resulting in plant height
    bacteria is transferred to another by the help       reduction
    of bacteriophage is (AIIMS 2000)                     (d) quantitative trait mutations
    (a) transformation (b) transduction
    (c) transcription     (d) configuration          71. The branch of science dealing with process
                                                         of improvement of human race by selective
63. Which one of the following pairs/names               breeding is called (AIIMS 1997)
    means one and the same thing? (AIIMS                 (a) euthenics      (b ) eugenics
    2003)                                                (c) euphenics      (d) obstetrics
    (a) Gene pool – Genome
    (b) Codon – Gene                                 72. Genetic engineering is related with (BHU
    (c) Cistron – Triplet                                2003)
    (d) DNA fingerprinting – DNA profiling               (a) eugenics       (b) euphenics
                                                         (c) euthenics      (d) all of these
64. Teminism is the same as (AIIMS 1995)
    (a) translation    (b) DNA synthesis             73. In transgenics, expression of transgene in
    (c) transcription  (d)reverse transcription          target tissue is determined by (CBSE 2004)
                                                         (a) enhancer          (b) transgene
65. The name of Tenim and Baltimore is                   (c) promoter          (d) reporter
    associated with (BHU 1994)
    (a) photorespiration                             74. DNA fingerprinting refers to (CBSE 2004)
                                                                                                   10

    (a) molecular analysis of profiles of DNA        81. Which of the following is related to genetic
    samples.                                             engineering ? (CBSE 1999)
    (b) analysis of DNA sample using                     (a) mutation       (b) plasmid
    imprinting device.                                   (c) plastid        (d) heterosis
    (c) techniques used for molecular analysis of
    different specimens of DNA.                      82. The term humulin is used for (CBSE 1999)
    (d) techniques used for identification of            (a) powerful antibiotic
    finger prints of individuals.                        (b) human insulin
                                                         (c) isoenzyme
75. Restriction endonucleases (CBSE 2004)                (d) hydrolytic enzyme
    (a) are present in mammalian cells for
    degradation of DNA when the cell dies.           83. High milk yielding varieties of cows are
    (b) are used in genetic engineering for              obtained by (CBSE 1999)
    ligating two DNA molecules.                          (a) super ovulation
    (c) are used for in vitro DNA synthesis.             (b) artificial insemination
    (d) are synthesized by bacteria as part of           (c) use of surrogate mother
    their defence mechanism.                             (d) all of these

76. Manipulation of DNA in genetic                   84. Which of the following is not a genetic
    engineering became possible due to the               vector ? (AFMC 2003)
    discovery of (CBSE 2002)                             (a) plasmid       (b) phage
    (a) restriction endonucleses                         (c) cosmid        (d) virusoid
    (b) restriction exonucleses
    (c) reverse transcriptase                        85. Which of the following cell is totipotent ?
    (d) DNA ligase                                       (AFMC 2000)
                                                         (a) meristem      (b) sieve tube
77. Introduction of food plants developed by             (c) cork          (d) xylem vessels
    genetic engineering is not desirable because
    (CBSE 2002)                                      86. Cloning is meant for (AFMC 1995)
    (a) economy of developing countries may              (a) production of hGH gene in E.coli.
    suffer                                               (b) to preserve the genotype of the organism.
    (b) these products are less tasty as compared        (c) to replace the original gene.
    to the already existing products.                    (d) all of these.
    (c) this method is costly.
    (d) there is danger of introduction of viruses   87. The Ti plasmid is often used for making
    and toxins with introduced crops.                    transgenic plants. The plasmid is found in
                                                         (CBSE 2004)
78. A bacterium which has found extensive use            (a) Azotobacter
    in genetic engineering work in plants is             (b) Rhizobium of the roots of leguminous
    (CBSE 2000)                                          plants.
    (a) Bacillus coagulans                               (c) Agrobacterium
    (b) Clostridium septicum                             (d) yeast as a 2μm plasmid
    (c) Xanthomonas citri
    (d) Agrobacterium tumefaciens                    88. An example of gene therapy is        (AFMC
                                                         2004)
79. Producing a giant mouse in the laboratory            (a) production of injectable hepatitis B
    was possible through (CBSE 2000)                     vaccine.
    (a) gene mutation (b) gene manipulation              (b) production of vaccines in food crops like
    (c) gene synthesis (d) gene duplication              potatoes which can be eaten.
                                                         (c) introduction of gene for adenosine
80. The first transgenic crop was (CBSE 1999)            deaminase in persons suffereing from SCID.
    (a) cotton           (b) pea                         (d) production of test tube babies by
    (c) tobacco          (d) flax                        artificial insemination and implantation of
                                                         fertilized eggs.
                                                                                                  11

                                                    94. Recombinant DNA technology is related
89. What is the first step in Southern blot             with (BHU 1999)
    technique ? (AIIMS 2004)                            (a) Stanley Cohen and Harbert Oyer
    (a) Denaturation of DNA on the gel for              (b) Bateson and Punnette
    hybridization with specific probes.                 (c) Huxley and Harvey
    (b) production of a group of genetically            (d) Schleiden and Schwann
    identical cells.
    (c) Digestion of DNA by restriction enzyme.     95. Which of the following cut DNA at specific
    (d) Danturation of DNA from a nucleated             sites? (CBSE 1997)
    cell such as the one from the scene of crime.       (a) Ligase         (b) EcoRI
                                                        (c) Exonuclease    (d) Alkaline phosphate
90. Assertion (A): Mast cells in the human body
    release excessive amounts of inflammatory       96. Plasmid is used as a carrier because
    chemicals which cause allergic reactions.           (Manipal 1999)
    Reason (R): Allergens in the environment on         (a) it has both ends with replicating points.
    reaching human body stimulate mast cells in         (b) it has no free ends.
    certain individual. (AIIMS 2003)                    (c) it is circular DNA with capacity of
    (a) both A and R are correct and R is a             binding with eukaryotic DNA.
    correct explanation of A.                           (d) All of the above.
    (b) both A and R are correct but R is not a
    correct explanation of A.                       97. The function of Polymerase Chain Reaction
    (c) A is true and R is false.                       is (CPMT 2003)
    (d) both A and R are false.                         (a) translation
                                                        (b) transduction
91. Restriction enzymes (AIIMS 2003)                    (c) DNA amplification
    (a) are endonucleases which cleaves DNA at          (d) none of these
    specific sites.
    (b) make DNA complementary to an                98. Genetically engineered bacteria is used in
    existing DNA or RNA.                                the production of (CPMT 2000)
    (c) cut or join fragments.                          (a) thyroxin       (b) human insulin
    (d) are required in vectorless direct gene          (c) epinephrine    (d) cortisol
    transfer.
                                                    99. Abnormal gene is replaced by normal gene
92. Assertion (A): Clones are produced by               through (DPMT 2004)
    sexual reproduction and same sexual                 (a) medicines     (b) gene therapy
    process.                                            (c) cloning       (d) radiation
    Reason (R): These are prepared by group of
    cells descended from many cells or by           100. Gene therapy involves (DPMT 2001)
    inbreeding of a heterozygous line. (AIIMS           (a) introduction of normal genes in a cell.
    2002)                                               (b) eliminating defective and useless genes.
    (a) both A and R are correct and R is a             (c) treating of defective genes with
    correct explanation of A.                           radiations.
    (b) both A and R are correct but R is not a         (d) replacement of defective genes by
    correct explanation of A.                           normal genes.
    (c) A is true and R is false.
    (d) both A and R are false.                     101. The nuclease enzyme, which begins its
                                                        attack from free end of a polynucleotide, is
93. Introduction of foreign gene for improving          (PPMT 2001)
    genotype is called (AIIMS 2002)                     (a) exonuclease     (b) kinase
    (a) tissue culture                                  (c) polymerase      (d) endonuclease
    (b) vernalization
    (c) genetic engineering                         102. Transgenic animals are those which have
    (d) eugenics                                        (DPMT 1997)
                                                        (a) foreign RNA in all its cells.
                                                                                                     12

    (b) foreign DNA in all its cells.               109. An analytical technique used foe solving
    (c) foreign DNA in some of its cells.               the paternity disputes based on DNA
    (d) both a and c.                                   polymorphism is called (KPMT 2003)
                                                        (a) DNA sequencing(b) DNA fingerprinting
103. Construction of recombinant DNA involves           (c) Cloning        (d) Cell culture
    (KCET 2002)
    (a) cleaving and rejoining DNA segments         110. A transgenic plant is one in which (AMU
    with endonuclease alone.                            2003)
    (b) cleaving DNA segments with                      (a) a gene from another plant is introduced.
    endonuclease and rejoining them with                (b) a gene from another organism bacteria is
    ligase.                                             introduced.
    (c) cleaving DNA segments with ligase and           (c) a gene from another organism virus is
    rejoining them with endonuclease.                   introduced.
    (d) cleaving and rejoining DNA segments             (d) all of the above.
    with ligase alone.
                                                    111. In gene therapy the DNA is inserted into a
104. Production of a human protein in bacteria          cell to compensate for (CMC 2003)
    by genetic engineering is possible because          (a) absence of plasmids
    (CBSE 2005)                                         (b) mutant allele
    (a) bacterial cell can carry out the RNA            (c) lack DNA
    splicing reactions.                                 (d) all of these
    (b) human chromosome can replicate in
    bacterial cell.                                 112. One of the following vaccine is not made
    (c) mechanism of gene regulation is                 from recombinant DNA technology
    identical in bacterial and human cell.              (Manipal 2003)
    (d) genetic code is universal.                      (a) FMD            (b) BCG
                                                        (c) hepatitis      (d) anthrax
105. cDNA probes are copied from the mRNA
    molecules with the help of (AIIMS 2005)         113. Rennet is used in (MPPMT 2002)
    (a) restriction enzymes                             (a) bread making (b) fermentation
    (b) reverse transcriptase                           (c) cheese making (d) antibiotics synthesis
    (c) DNA polymerase
    (d) adenosine aminase                           114. Modified antibiotics are manufactured by
                                                        the technique of (AIIMS 1998)
106. Maximum application of animal cell culture         (a) ultrafilteration (b) ultracentrifuge
    technology today is in the production of            (c) vernalization    (d) biotechnology
    (CBSE 2003)
    (a) insulin       (b) interferons               115. Vaccine is a (DPMT 1998)
    (c) vaccines      (d) edible proteins               (a) collection of antibiotics
                                                        (b) collection of life saving drugs
107. Which of the following discoveries resulted        (c) collection of lysins
    in a Noble Prize ? (CBSE 2003)                      (d) collection of killed diseased bacteria
    (a) X-rays induce sex-linked recessive lethal
    mutations.
    (b) Cytoplasmic inheritance.
    (c) Recombination of linked genes.
    (d) Genetic engineering.

108. Somatoclonal variations occur during
    (AMU 2003)
    (a) meiosis        (b) mitosis
    (c) tissue culture (d) all of these
                                                                                                        13



                                            ANSWERS # 15

        1. a   2. d   3. d   4. d   5. b   6. c   7. d   8. a   9. d   10.d
        11. c 12. d  13. d  14. b  15. a  16. b 17. a 18. b     19. c 20. a
       21. b   22. c 23. b  24. b  25. b  26. d 27. a 28. b     29. c  30. c
       31. b  32. d   33. c 34. a  35. b  36. a 37. a 38. b 39. b     40. b
       41. b  42. b  43. d   44. c 45. b  46. a 47. d 48. d 49. d     50. b
        51. c 52. a  53. b   54. c 55. d  56. b 57. d 58. a 59. b     60. d
       61. b  62. b  63. d  64. d   65. c 66. a 67. a   68. c  69. d   70. c
       71. b  72. b   73. c  74. c 75. d  76. a   77.d  78. d 79. b    80. c
       81. b  82. b  83. d  84. d  85. a  86. d   87. c 88. c   89. c 90. a
       91. a   92. d 93. c  94. a  95. b  96. c   97. c 98. b 99. b 100. d
       101. a 102. b 103. b 104. d 105. b 106. c 107. d 108. c 109. b 110. d
       111. b 112. b 113. c 114. d 115. d


                                         EXPLANATION # 15

1. (a): Plasmids are used to as vectors in the cloning of recombinant DNA.

3. (d): Restriction enzymes are used for cutting the DNA double helix at specific sites into fragments
containing “gene of interest”.

5. (b): DNA/RNA probes are prepared for commercial purposes and are believed to be the most
sophisticated and sensitive means to identify genes or specific DNA sequences.

20. (a): DNA-RNA hybrid is formed during the formation of cDNA from RNA (reverse transcription); the
enzyme involved is reverse transcriptase

31. (b): In DNA fingerprinting, the isolated DNA is subjected to Southern blotting where the
nitrocellulose filter is containing the DNA is dried and exposed to P32 labelled mRNA.

74. (c): DNA fingerprinting is based on the fact that the DNA of each individual is interrupted by a series
of identical DNA sequences called repetitive DNA or tandem repeats. The pattern, length and number of
these repeats are unique for each individual. In this technique identity of a person with the help of blood
stains, semen or hair root is possible with absolute certainty.

95. (b): EcoRI, isolated from Escherichia coli, is a type of restriction enzymes used for cutting DNA at
specific sites.

100. (d): Gene therapy is the treatment of disease by replacing, altering or supplementing a gene that is
absent or abnormal and whose absence or abnormality is responsible for the disease.

				
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