Class 12 biology chapter 12 Biotechnology solutions
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Q. 1 Choose the correct option
1. The bacterium which causes a plant
disease called crown gall is …………….
b. Helicobacter pylori
c. Agrobacterium tumifaciens
d. Thermophilus aquaticus
e. Bacillus thuringienesis
2. The enzyme nuclease hydrolyses
…………… of polynucleotide chain of
DNA.
a. hydrogen bonds
b. phosphodiester bonds
c. glycosidic bonds
d. peptide bonds
3. In vitro amplification of DNA or RNA
segment is known as ……………
a. chromatography
b. southern blotting
c. polymerase chain reaction
d. gel electrophoresis
4. Which of the following is the correct
recognition sequence of restriction
enzyme hind III.
a. 5’ —A-A-G-C-T-T—3’
3’ —T-T-C-G-A-A— 5’
b. 5’ —G-A-A-T-T-C—3’
3’ —C-T-T-A-A-G— 5’
c. 5’ —C-G-A-T-T-C—3’
3’ —G-C-T-A-A-G— 5’
d. 5’ —G-G-C-C—3’
3’ —C-C-G-G— 5’
5. Recombinant protein ……………… is used to dissolve blood clots present in the body.
a. insulin
b. tissue plasminogen activator
c. relaxin
d. erythropoietin
6. Recognition sequence of restriction
enzymes are generally ……………
nucleotide long.
a. 2 to 4
b. 4 to 8
c. 8 to 10
d. 14 to 18
Q. 2 Very short answer type questions.
1. Name the vector which is used in
protuction of human insulin through
recombinent DNA technology.
Answer : In recombinant DNA technology, plasmids are often used as vectors, DNA molecules that carry DNA fragments from one organism to another.
2. Which cells from Langerhans of
pancreas do produce a peptide hormone
insulin?
Answer : The beta cell produces the hormone insulin and makes up approximately 75 percent of each islet. Elevated blood glucose levels stimulate the release of insulin. The delta cell accounts for four percent of the islet cells and secretes the peptide hormone somatostatin.
3. Give the role of Ca++ ions in the transfer of recombinent vector into bacterial host cell.
Answer : It increases the ability of a prokaryotic cell to incorporate plasmid DNA allowing them to be genetically transformed. … Positively charged calcium ions attract both the negatively charged DNA backbone and the negatively charged groups in the LPS inner core.
4. Expand the following acronyms which
are used in the field of protechnology.
i. YAC
Answer : YACs are plasmid shuttle vectors capable of replicating and being selected in common bacterial hosts such as Escherichia coli, as well as in the budding yeast Saccharomyces cerevisiae. Yeast artificial chromosome (YAC) is a human-engineered DNA molecule used to clone DNA sequences in yeast cells.
ii. RE
Answer : Restriction enzymes. In the laboratory, restriction enzymes (or restriction endonucleases) are used to cut DNA into smaller fragments. The cuts are always made at specific nucleotide sequences.
iii. dNTP
Answer : Using dNTP during the extension phase provides single bases ready to go into DNA and double it, like building blocks. Since the purpose of the technique is to synthesize new DNA, dNTP provides nucleotides to the “unzipped” strand using the template of a single side.
iv. PCR
Answer : The polymerase chain reaction (PCR) is used to make millions of copies of a target piece of DNA. It is an indispensable tool in modern molecular biology and has transformed scientific research and diagnostic medicine.
v. GMO
Answer : Some benefits of genetic engineering in agriculture are increased crop yields, reduced costs for food or drug production, reduced need for pesticides, enhanced nutrient composition and food quality, resistance to pests and disease, greater food security, and medical benefits to the world’s growing population.
vi. MAC
Answer : A mammalian artificial chromosome (MAC) could be used for transferring genes into cells which could be beneficial for gene therapy and in the production of transgenic animals.
5. Fill in the blanks and complete the chart.
Answer :
i. Bt cotton is an insect-resistant transgenic crop designed to combat the bollworm.
ii. ethylene gas
iii. Golden rice is genetically modified in order to produce beta carotene,
iv. Holsteins are known for their outstanding milk production
Q. 3 Short answer type questions.
1. Explain the properties of a good or ideal cloning vector for rDNA technology.
Answer : A good vector should have the ability of independent replication so that as the vector replicates (through ori gene) and large number of copies of the DNA insert will be formed.Moreover vector should be able to easily introduce into host cells.
A vector should have marker genes for
antibiotic resistance; must contain unique
cleavage site in one of the marker genes for
restriction enzyme; it should have at least
suitable control elements like promoter,
operator, ribosomal binding sites, etc
2. A PCR machine can rise temperature
upto 100°C but after that it is not able
to lower the temperature below70°C
automatically. Which step of PCR will
be hampered first in this faulty machine? Explain why?
Answer : Denaturation step hampered first because denaturation occur at 94° C.
3. In the process of rDNA technology, if two separate restriction enzymes are used to cut vector and donor DNA then which problem will arise in the formation of rDNA or chimeric DNA? Explain.
Answer : Importantly, restriction enzymes do not cut randomly; rather, they cut at specific DNA target sequences, which is one of the key features.
4. Match and write the pairs.
Answer :
i – g
ii- e
iii – f
iv – a
v – c
vi – b
Q. 4 Long answer type questions.
1. Define and explain terms.
i. Biopiracy : Biopiracy is
defined as ‘theft of various natural products and then selling them by getting patent without giving any benefits or compensation back to the host country’. In short, it is unauthorized misappropriation of any biological resource and indigenous knowledge.
ii. Biopatent: Biopatent is a patent granted by the government to the inventor for biological entities and for products obtained from them. For example, basmati rice and neem based products are biopatents of India.
iii. Bioethics : Bioethics is the study of the ethical issues emerging from advances in biology and medicine. It is also moral discernment as it relates to medical policy and practice.
2. Explain the steps in process of rDNA
technology with suitable diagrams.
Answer :
The steps involved in gene cloning are as
follows :
a. Isolation of DNA (gene) from the donor organism :
i. The desire gene to be cloned has to be
obtained from the source organism (donor). Initially the cells of the donor organism are
sheared with the blender and treated with
suitable detergent. Isolated purified DNA is then cleaved by using restriction enzymes particularly Restriction Endonucleases (RE).
b. Insertion of desired foreign gene into a cloning vector (vehicle DNA) :
The foreign DNA or passanger DNA is now
inserted into a cloning vector or vehicle DNA. The most commonly used cloning vectors are plasmids of bacteria and the bacteriophage viruses like lamda phage and M13. The most commonly used plasmid is pBR 322.
e. Multiplication of transformed host cell:
Once transformed, host cells are separated
by the screening process. In this step the
transformed host cells are introduced into fresh culture media. At this stage the host cells divide and redivide along with the replication of the recombinant DNA carried by them.
f. Expression of the gene to obtain the desired product:
The next step involves the production
of desired products like alcohol, enzymes,
antibiotics, etc. Finally the desired product is separated and purified through downstream processing using suitable bioreactor.
3. Explain the gene therapy. Give two types of it.
Answer : 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. A gene is a stretch of DNA required to
make a functional product such as part or all of a protein. During gene therapy, DNA that codes for specific genes is delivered to individual cells in the body. In other conditions, such as high cholesterol and high blood pressure, genetic and environmental factors interact to cause
disease. There are more than 5000 different human genetic diseases known to be caused by single gene defects e.g. sickle cell anaemia, thalassemia, Tay-sach’s disease, cystic fibrosis, Huntington’s chorea, haemophilia, alkaptonuria, albinism, etc.
Gene therapy is being used in many ways.
For example, to:
• Replace missing or defective genes;
• Deliver genes that speed the destruction of
cancer cells;
• Supply genes that cause cancer cells to
revert back to normal cells;
• Deliver bacterial or viral genes as a form
of vaccination;
• Deliver DNA to antigen expression and
generation of immune response;
• Supply of gene for impairing viral
replication;
• Provide genes that promote or impede the
growth of new tissue; and
• Deliver genes that stimulate the healing of
damaged tissue.
4. How are the transgenic mice used in
cancer research?
Answer : These mice provide valuable clues about the biological function of a normal gene. In translational cancer research, this represents a powerful tool in assessing the potential validity of targeted therapy because the targets can be precisely inactivated in the setting of a developing or developed tumor.
5. Give the steps in PCR or polymerase
chain reaction with suitable diagrams.
Answer : Polymerase chain reaction (PCR) is another device used for gene cloning or gene multiplication in vitro. It is the amplification of gene of interest, through PCR.In 1985, Kary Mullis made an important discovery (contribution) in the form of an extremely powerful technique called polymerase chain reaction (PCR). PCR can generate a billion copies of the desired segment of DNA or RNA,
Mechanism of PCR:
At the start of PCR, the DNA segment,
and excess of two primer molecules, four
deoxyribonucleosides triphosphates and the thermostable DNA polymerase are mixed together in ‘eppendorf tube’ and the following operations are performed sequentially.
Step i : The reaction mixture is heated to a
temperature (90–98 oC) to separate two strands of desired DNA. This is called denaturation.
Step ii : The mixture is allowed to cool
(40–60 oC) that permits pairing of the primer to the complementary sequences in DNA. This step is called annealing.
Step iii : The temperature (70–75 oC) allows thermostable Taq DNA polymerase to use
single-stranded DNA as template and adds
nucleotides. This is called primer extension. It takes arround two minutes duration.
6. What is a vaccine? Give advantages of
oral vaccines or edible vaccines.
Answer : A vaccine is a biological preparation that provides active acquired immunity against a certain disease. Usually a vaccine consists of a biological agent that represents the disease-causing microorganism. It is often made from a
weakened or killed form of the microorganism.
Edible vaccines have efficient mode of action for immunization, as they do not require subsidiary elements to stimulate immune response. Edible vaccine unlike traditional vaccines brings forth mucosal immunity.
Oral vaccination provides both social and economic advantages, especially in developing countries. The use of needle-free vaccine administration eliminates the risk of transmitting blood-borne pathogens and can be performed by health workers without any medical training.
7. Enlist different types of restriction
enzymes commonly used in rDNA technology? Write on their role.
Answer : Enzymes : Different enzymes include Lysozymes, Nucleases such as exonucleases endonucleases, restriction endonucleases, DNA ligases, DNA polymerases, alkaline phosphatases, reverse transcriptases, etc.
Enzymes that cut the phosphodiester bands
of polynucleotide chains are called nuclease. There of two types – exonuclease and endonuclease. Exonucleases cut nucleotides from the ends of DNA strands whereas endonuclease cut DNA from within. The phosphodiester back bone at highly specific sites on both strands of duplex, is cut by these enzymes, called restriction endonucleases or simply restriction enzymes.
The restriction enzymes are thus the
molecular scissors that are used to recognize and cut DNA at specific sequences. The sites recognized by them, are called recognition
sequences or recognition sites.
8. Enlist and write in breif about the
different biological tools required in rDNA technology.
Answer : There are three types of biological tools used viz, enzymes, cloning vectors (vehicle DNA) and competent host (cloning organisms) for transformation with recombinant DNA.
A. Enzymes : Different enzymes include
Lysozymes, Nucleases such as exonucleases endonucleases, restriction endonucleases,
DNA ligases, DNA polymerases, alkaline
phosphatases, reverse transcriptases, etc.
B. Cloning vectors (vehicle DNA) – Vectors
are DNA molecules that carry a foreign
DNA segment and replicate inside the host cell. Vectors may be plasmids,
bacteriophages (M13, lambda virus),
cosmid, phagemids, BAC (bacterial
artificial chromosome), YAC (yeast
artificial chromosome), transposons,
baculoviruses and mammalian artificial
chromosomes (MACs),. Most commonly
used vectors are plasmid vectors (pBR
322, pUC, Ti plasmid) and bacteriophages
(lamda phase, M13 phage).
C. Competent host (cloning organism) used are usually the bacteria like Bacillus
haemophilus, Helicobacter pyroli and E.
coli. Mostly E. coli is used for the transformation with recombinant DNA.