Class 12

Class 12 Biotechnology Sample Question Paper 2020 Solved

Class 12 Biotechnology Sample Paper 2020

Time allowed: 3 hours

Maximum Marks: 70

SECTION A

1. Name any two scientists involved in designing the first recombinant DNA molecule.

Ans: Paul Berg, Herbert Boyer, Annie Chang, and Stanley Cohen.

2. Write any two properties which can be improved through protein engineering.

Ans: Properties for thermal and pH stability/ solvent tolerance, and solubility/ catalytic potency, etc.

3. Transgenic plants have been developed to survive in a saline habitat. Which technique might have been used to develop such plants?

Ans: By the production of stress-related osmolytes like sugars (e.g. trihalose and fructans)/ sugar alcohols (e.g. mannitol) / amino acids (e.g. proline), glycine betaine/ certain proteins (e.g. antifreeze proteins).

4. Which vector was used in the first cloning experiment involving a mammalian cell?

Ans: Simian Virus 40

How does a modification enzyme protect its own DNA from digestion?

Ans: Methylation

5. What was the strategy behind the Human Genome Project? 1

Ans: To make a series of maps of each human chromosome at increasingly finer resolutions.

6. An enriched medium containing salts, glucose, proteins, and vitamins was made, and a commercially available animal cell line was introduced. However, the cells began dying. What could be the reason behind it?

Ans: Serum/FCS, an essential component of animal cell culture media, was missing.

What is A in the flow chart?

Ans: Trophoblast

7. Margaret Dayhoff observed that protein sequences undergo variation according to certain patterns. Write any one such pattern.

Ans: Amino acids were not replaced at random but were altered with specific preferences./ Some amino acids such as tryptophan, was generally not replaced by any other amino acid / Based on several homologous sequences, a point accepted mutation (PAM) matrix could be developed.

What is the underlying principle of “Molecular evolution”?

Ans: Functionally related or homologous protein sequences are similar.

8. Crystallisation is not required due to the advent of which of the following new technique?

a) X-ray crystallography
b) NMR
c) Sanger’s method of protein sequencing
d) Edman’s method of protein sequencing

9. Optimum pH for plant tissue culture medium is-

a) 7.5
b) 5.7
c) 8
d) 8.5

10. The single-letter codes for Tyrosine and Asparagine are

a) N and Y
b) A and T
c) T and A
d) Y and N

11. The disease due to the deficiency of the enzyme Adenosine Deaminase (ADA) is

a) SCID
b) Thalassemia
c) Haemophilia
d) Mad cow disease

Ans:

12. Question numbers 12(i) to 12(iv) are based on the following text on characterization of Cell Lines:

In order to analyze the growth characteristics of a particular cell type or cell line, a growth curve can be established from which one can obtain a population doubling time, a lag time, and a saturation density. A growth curve generally will show the cell population’s lag phase, that is, the time it takes for the cells to recover from subculture, attach, and spread; the log phase, in which the cell number begins to increase exponentially and a plateau phase, in which the growth rate slows or stops due to depletion of growth factors and nutrients.

(i). Beyond what cell concentration, saturation density is achieved?

a) > 10⁴ cells /ml
b) 10⁴ to 105 cells /ml
c) > 10⁵ cells /ml
d) > 10⁶ cells /ml

(ii). There is no increase in the cell concentration in the lag phase due to the following reasons:

a) Exhaustion of the medium.
b) Space constraint
c) Both “a” and “b”
d) Acclimatization to the new environment.

(iii). In which phase of growth is the specific growth rate of animal cell calculated?

a) Log phase
b) Lag phase
c) Stationary phase
d) Decline phase.

(iv) A student adds antibiotic to the animal cell culture medium and still obtains the same growth curve. The probable explanation for it will be:

a) Antibiotics add growth factors and hormones in the medium
b) Antibiotics provide serum for the growth of animal cells.
c) Antibiotics enhance the nutrient content of the medium.
d) Antibiotics don’t have any effect on animal cells

SECTION B

13. Differentiate between synthetic and complex medium used for microbial culture. 2

Ans: Synthetic media – Full composition of the medium is known.

Semi-synthetic media – These media contain highly complex components such as peptone, beef extract, yeast extract or casein digest.

Nutrient broth/ Typticase soya broth (TSB) / Brain heart infusion (BHI) broth.

14. How can LEU 2 gene be used as a selectable marker? 2

Ans: LEU2 gene codes for an enzyme required for the synthesis of amino acid leucine.

Yeast cells having this plasmid can grow on a medium lacking leucine and hence can be selected.

e.g. Yep

15. On the basis of the table given below, state your observations pertaining to the organisation features of the organism.

ORGANISM	No. of chromosomes	Genome size inbase pairs	The number ofpredicted genes	Part of thegenome thatencodes forproteins
Worm: Caenorhabditiselegans	6	100,000,000	19,000	27%
Human: Homo sapiens	23	3,000,000,000	20,000-25,000	<5%
Fly Drosophilamelanogaster	4	175,000,000-196,000,000	13600	20%

Ans: No simple correlation between the intuitive complexity of an organism and the number of genes in its genome.

A relatively small number of genes in a human genome in comparison to worm /Drosophila melanogaster.

16. Differentiate between somaclones and gametoclones. Who proposed the term somaclones?

Ans: While somaclones are plant variants obtained from tissue cultures of somatic tissues, gametoclones are plant variants with gametophytic origin obtained from tissue such as pollen or egg cell.

Larkin and Scowcroft (1981) proposed the term ‘somaclones’

17 a) What are the various interactions that stabilize a folded protein?

b) How can the stability of a protein be changed?

Ans: A balance between the stabilizing (mainly hydrophobic) interactions and destabilization interactions.

By substituting amino acids that either favour stabilizing interactions in a folded protein or destabilizing interactions in an inactive protein.

18. What are the various biosafety issues in microbial technology?

Ans: Potential of genetically modified organisms (GMO) or recombinant strains to infect other organisms./Toxicity and allergy associated with the use of recombinant molecules./ Increasing the environmental pool of antibiotic-resistant microorganisms or transfer of antibiotic-resistant genes./Problems associated with the disposal of spent microbial biomass./Safety aspects associated with contamination, infection, or mutation of process strains.

The laboratory scale design cannot be scaled up to an industrial scale directly. Write any two points that need to be considered while going for industrial-scale production.

Ans: Bulk purchase of chemicals and other raw materials would bring down costs.

• The labour cost decreases sharply with an increase in production.

19. In a variant of chymotrypsin, Asp 102 is replaced by Glu 102. Do you expect the enzyme to retain activity? Schematically indicate the role of amino acid residues participating in catalysis.

Ans:

Negatively charged Asp 102 partially borrow hydrogen ion from His-57.
His-57 attracts hydrogen ion from adjacent Ser 195
Serine 195 gets negative charge.
Serine 195 makes a nucleophilic attack on the protein substrate.

Thalassemic patients produce excess alpha or beta subunits of haemoglobin leading to impaired oxygen-binding capacity by their erythrocytes. How can it be determined as to which subunit is produced in excess?

Ans: Normal and thalassemic erythrocytes were obtained and their lysates analysed. Protein fingerprinting/ 2-D gel electrophoresis/ MALDI/ SDS-PAGE can identify if the alpha or beta chain is absent

Protein fingerprinting:

• Trypsin digestion of Purified haemoglobin
• Paper electrophoresis followed by paper chromatography.
• Spray with ninhydrin.

SECTION C

20. Recombinant insulin is produced at 100 mg/l by E. coli at a cell concentration of 1g/l. Calculate the volume of the reactor (size of the fermentor) needed to produce 1 kilogram of insulin in the following conditions:

(a) When the cell concentration is 1 g/l and insulin production is 100 mg /l.
(b) When the cell concentration is 50 g/l and insulin production is 100 mg /l.
(c) When the cell concentration is 50 g/l and insulin production is 500 mg /l

Ans: (a) Insulin production is 100 mg/L; so fermentor volume needed for 1 Kg of insulin is 1 Kg /100mg = 1000, 000mg/100,g = 10,000mg = 10,000L.

(b) Cell concentration is increased 50 times, we need 200 L reactor.

(c) Insulin yield per litre of culture is 500 X 50 = 25, 000 mg / L which is 25gram/L. We need a 40 L reactor (1000g/25g) .

21. Schematically explain the formation of a recombinant plasmid.

Ans:

Students of Class XII visited Microbial Type Culture Collection, Chandigarh and observed microbial cultures of Providencia stuartii, Streptomyces albus and Haemophilus aegyptus. Name the restriction enzymes obtained from them and also specify their restriction sites.

Ans:

Haemophilus aegyptus HaeIII 5’G-G-C-C 3’

3’C-C-G-G 5’

Providencia stuartii PstI 5’C-T-G-C-A-G 3’

3’G-A-C-G-T-C 5’

Streptomyces albus SalI 5’G-T-C-G-A-C 3’

3’C-A-G-C-T-G 5′

22. Complete the table by filling in the mode of action / functional properties indicated as A, B, C, D, E, and F.

Functional Property	Mode of action
Whipping/Foaming	A
B	Formation and stabilization of fat emulsions
C	Protein matrix formation and setting
Viscosity	D
E	Hydrogen bonding of water; entrapment of water
Solubility	F

Ans:

A- Forms a stable film
B- Emulsification
C- Gelation
D- Thickening, water binding
E- Water binding
F- Protein salvation

23. Selection is an important step in genetic engineering. You are given ampicillin and tetracycline antibiotics. Using these antibiotics, which selection technique could be used to differentiate between recombinant and non-recombinant cells?

Ans: Replica plating.

Host cells are first plated (master plate) on solid media with the desired antibiotic overnight.
Velvet paper is aligned, pressed on the master plate.
With the same alignment, it is pressed onto the replica plate.
Keep it overnight, transformed colonies will not grow in the replica plate
The colonies having insert can easily be scored off from the master plate by comparing the two plates.

24. Write any six applications of plant genetic engineering. 3

Ans: Production of healthy oils with altered fatty acid profiles.

Modification of starch properties for specific uses.
Favourable change of grain storage products and their chemical composition to improve the processing of bread making with wheat flour, malting of barley, and brewing of beer.
Removal of undesirable toxic compounds in certain plants.
Development of blue roses/ blue coloured cotton, which is otherwise not possible by conventional plant breeding because of the absence of blue pigment in roses/ cotton
Development of tearless onions, caffeine-free coffee, and low-nicotine tobacco. (Any three)

25. How does the metagenomics approach help to identify novel genes present in the environment? Explain the process.

Ans: The collective DNA(from various environmental niche) is subjected to restriction digestion using restriction endonucleases and the fragments are cloned into suitable vectors.

The clones are then screened for presence of a variety of molecules.
The clones expressing novel molecules or molecules with improved
characteristics are used for large-scale production by fermentation techniques.

What is a pilot plant? Why is it necessary to validate a process in a pilot plant before commercial-scale production in a bioprocess industry?

Ans: Pilot plant: Mini version of the commercial plant.

Direct production of microbes on a large or commercial scale has the risk of not only large investments, but also producing products, which may not be of appropriate quality so that there are problems in their commercialization.

26. Given below are few transgenic crops approved by US Food and Drug Administration along with the improved character. Name the genes A to F introduced for the improved character.

Crop	Gene	Improved character
Canola	A	Hybrid production
Corn	B	Insect resistance
Cotton	C	Insect resistance
Papaya	D	Virus resistance
Potato	E	Insect and virus control
Soyabean	F	Weed Control

Ans:

A: Thioesterase EPSP synthase/
B: Bt cry I Ac
C: Acetolactate synthase, Nitrilase, EPSP synthase, Bt CryIA(c)
D: Coat protein
E: Bt CryIIIA and coat protein/
F: EPSP synthase

SECTION D

27. Mutation is an alteration in any of the base of a DNA sequence sometimes leading to a defective protein or prematurely terminated non-functional protein. It can be spontaneous or induced. Diagrammatically explain how mutation can be induced in a gene.

Ans:

A bacteriophage is known to infect E.coli with pili. How can it be modified to serve as a suitable vector? What are the major advantages of developing vectors based on such bacteriophages?

Ans: Foreign DNA can be inserted into the bacteriophage single-stranded, circular DNA of 6407 bp without disrupting any of the essential genes.

Its genome is less than 10 kb in size.
RF can be purified and manipulated exactly like a plasmid.
Genes cloned into M13-based vectors can be obtained in the form of single-stranded DNA.

28. Explain the non-covalent interactions involved in organizing the structure of protein molecules.

Ans: Ionic bonds:

Interactions between the oppositely charged groups are also known as salt bridges

Hydrogen bonds: Hydrogen bonds are formed by the “sharing” of a hydrogen atom between two
electronegative atoms such as Nitrogen and Oxygen.
Van der Waals forces: The Van der Waals types of forces are essentially contact forces, proportional to the surface areas in contact.
Hydrophobic interactions: The hydrophobic interaction is a manifestation of the hydrogen bonding network in water. In water, each molecule is potentially bonded to four other molecules through H-bonds.

29. Which two main methodologies are used for genome sequencing? Explain.

Ans: Directed sequencing of Bacterial Artificial Chromosome (BAC) contigs

Bacterial Artificial Chromosome (BAC) vectors are used to make genomic libraries in which the insert size is 80-100 kb, library is then screened by finding common restriction fragments.
BAC clones are then mapped to find overlapping arrays of contiguous clones called contigs. The mapped contigs are sequenced by breaking large DNA fragments into small pieces.

Random shotgun sequencing

In random shotgun sequencing, big genomic DNA molecules are cloned in small (2.0 kb) and medium (10 kb) plasmid vectors, and a library is constructed.
Picking many clones, sequencing them, and feeding all this data into a computer program, these sequences are joined by finding overlapping parts.
The result is, we get long pieces of DNA sequences.

Explain the diseases caused by single gene mutations following Mendelian inheritance, specifying the genomic location, inheritance pattern, and mutation. Name any two diseases showing gene polymorphism with complex inheritance.

Ans: Cystic Fibrosis (Cystic Fibrosis Trans membrane Conductance Regulator CFTR gene)

1. Inheritance: autosomal recessive disease
2. Genomic location: Chromosome 7 (7q31.2)
3. Mutation: The most common mutation is a deletion of 3 bps resulting in the loss of codon no. 508, which codes for phenylalanine

Huntington disease (Huntington’s gene HTT)

1. Inheritance: autosomal dominant
2. Location: Chromosome 4 (4p16.3)
3. Mutation: increased number of CAG repeats more than 35 times

Two diseases showing gene polymorphism with complex inheritance

Common late-onset Alzheimer’s disease
Migraine

30. Diagrammatically show the cultivation of adult stem cells from bone marrow and their differentiation into specialized cells. Name two scientists who established the field of stem cell research. For which medical conditions, stem cells can be used (Write any two)?

Ans: Cultivation of adult stem cells from bone marrow and their differentiation into specialized cells.

Ernest McCulloch and James Till: Leukemia (Cancerous blood cells), Heart disease, heart attack (cardiac tissue damage). Paralysis (spinal cord injury). Alzheimer’s, Parkinson’s, Huntington’s (dead brain cells).and Burns (damaged skin cells).