Notes

Class 12 Biotechnology Sample Question Paper 2018 Solved

Class 12 Biotechnology Sample Paper 2018

Time allowed: 3 hours

Maximum Marks: 70

SECTION A

1. Specify the role of “cos” sites in bacteriophage lambda.

Ans: “cos” sites are important for packaging DNA into the phage head.

2. Expand and define PER.

Ans: Protein Efficiency Ratio.

PER is used as a measure of growth expressed in terms of weight gain of an adult by consuming 1g of food protein.

3. What would be the effect of an aqueous environment on the bond strength of ionic bonds between amino acid residues in a protein?

Ans: The bond strength decreases due to the insulating properties / dielectric strength of water.

4. How is lipofection used to deliver genes into cells?

Ans: Gene is transferred with the help of tiny vesicles of bipolar phospholipids that fuse with the cell membrane, releasing the DNA into the cytoplasm.

5. Name the scientists who were first to introduce trypsin for the subculturing of adherent cells.

Ans: Rous and Jones.

6. Write any one distinguishing feature of pBR 322 and pUC19 vectors.

Ans:

BAC	YAC
Effective against Bacteria	Effective in Yeast
It has genes for maintenance andreplication of the F-factor	It has telomere, centromere and ARS fromyeast chromosome
Can accommodate up to 300kb of DNA	It can be used for cloning DNA up to 1 MB in size.

SECTION B

7. What is meant by tissue engineering?

Ans: Tissue engineering: Naturally derived or synthetic materials may be engineered into “scaffolds” that, when implanted in the body, could provide a template that allows the body’s own cells to grow and form new tissues. Such implants could function without triggering immune responses. Genetically-modified animals may also provide a source of cells, tissues, and organs for xenografts.

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

Ans: The Metagenomics approach has been developed to identify and select microbial genes synthesizing novel molecules. This approach directly utilizes the large number of microbial genomes present in an environmental niche, for example, in soil, in water, such as the ocean, or in the human gut. These genomes are contributed by both the culturable and the non-culturable varieties of microbes and together constitute what has been termed the metagenome. The collective DNA is extracted from a sample of soil, water, or any other environmental niche. It is subjected to restriction digestion using restriction endonucleases, and the fragments are cloned into suitable vectors. The clones are then screened for the presence of a variety of molecules.

9. Explain various plant regeneration pathways.

Ans: The plants can be regenerated by either organogenesis or somatic embryogenesis.

Organogenesis means the formation of organs, like shoots, from the cultured explants. Miller and Skoog experimentally proved that the formation of shoots or roots first on the cultured tissue depends on the relative concentration of auxin and cytokinin. If auxins are high in the medium, then it promotes rooting, while if cytokinins are high, shoot formation is promoted.

In somatic embryogenesis, the totipotent cells may undergo the embryogenic pathway to form somatic embryos, which can be grown to regenerate into complete plants.

Generally, somatic embryos resemble the zygotic embryos (seed embryos) except in their place of origin and larger size. For the first time, Steward in 1958 and Reinert in 1959 independently reported the somatic embryogenesis from carrot cultures.

10. A researcher wants to introduce a desired gene into a specific host cell. Write any two methods that can be used for the same purpose.

Ans:

1. Transformation: In this technique. We put the recombinant DNA in the medium having host cells. Host cells will take up the desired DNA provided the host cells are competent. If they are not competent, we make them competent by treating them with cold calcium chloride. Mandel and Higa proposed the technique in 1970.
2. Transfection: The desired DNA is mixed with the cationic liposomes or dextran and layered on the host cells, and is then taken inside by the host cells.
3. Electroporation: We pass electricity of the desired voltage through the culture of the cells, resulting in transient ( temporary ) pores in the cell membrane, and through these pores, DNA enters.
4. Biolistics ( Use of gene gun ): We use gold or tungsten particles and layer the DNA on them and bombard these bullets into the culture of the cells.
5. Use of modified bacteriophages to deliver the desired gene into the bacterial cell. Use of modified Agrobacterium tumefaciens to deliver the desired gene into the plant cell

11. Differentiate between somaclonal variations and gametoclonal variations. Who proposed the term “Somaclones” for plant variants?

Ans: Plants regenerated from long-term callus and cell suspension culture are often associated with chromosomal variations known as somaclonal variation.

If the tissue from which the variants have been obtained is having gametophytic origin such as pollen or egg cell, such variation is called Gametoclonal variation.

Larkin and Scowcroft (1981) proposed the term ‘somaclones’ for plant variants obtained from tissue cultures of somatic tissues

12. C. elegans is an eukaryotic organism with a genome of 97 Mb and about 20,000 genes. Why are the organizational features of this genome unusual when compared to the genomes of other eukaryotes, such as yeast and Drosophila?

Ans: It shows inaccuracy in gene prediction

There is no correlation between the intuitive complexity of an organism with that of other eukaryotes

Yeast encodes 70 percent of proteins, whereas worm and fruit fly encode 20- 25%

13. Highlight graphically the differences between culturing microbes in the school laboratory and a bioreactor, which allows cells to grow in a continuous culture system.

Ans: Graph of batch culture

Graph of continuous culture

14. How can you maximize protein stability during purification? Write any two parameters for the same.

Ans:

i)Maintenance of pH
ii)Maintenance of physiological conditions (CO₂, temperature)
iii)Use of inhibitors to prevent the action of proteolytic enzymes
iv)Avoidance of agitation or addition of chemicals that may denature the protein
v)Minimize processing time

SECTION C

15. Discuss the various types of shapes & structures that a protein takes to make a functional protein. Write various forces responsible for these structures.

Ans: The non-covalent interaction is involved in organizing the structure of a protein molecule.

Proteins fold into secondary structure, α-helix, and β-pleats.

Secondary Structure undergoes further folding into domains, motifs called tertiary structures.

Multimeric proteins are organized as Quaternary structures.

Various forces are responsible for these structures.

Hydrophobic interactions, electrostatic interactions, Hydrogen bonding, and van der Waals
forces are the non-covalent forces. (Any two)

16. Outline the process of creating of chimeric mouse by embryonic stem cell culture.

Ans:

17. What is a DNA probe? Explain the principle of Sanger’s method of DNA sequencing.

Ans: DNA Probe: It is a small sequence of DNA that recognizes and binds to its complementary sequence.

Sanger’s Method: Whenever ddNTP comes into the DNA synthesis, further synthesis of DNA stops.

It must indicate the following reagents:

Single-strand DNA, which needs to be sequenced.
A primer with a free 3’-OH.
DNA polymerase
dNTPs
ddNTPs
Primer extension in 4 different tubes, each containing a specific ddNTP at low concentration.
Termination at the point where ddNTP is incorporated.
Gel electrophoresis

18 Expand BLAST. Differentiate between Homologues and Paralogs.

Ans: BLAST: Basic Local Alignment Search Tool

Homologues represent the similarity due to common ancestry, and they will have the same function.
Paralogs represent similarities due to random chance and may differ in function

19. You have succeeded in purifying a protein from yeast. Name a technique you would use and the principle behind it for determining the molecular mass of this protein.

Ans: Mass spectrometry.

Principle of Mass spectrometer: It determines the molecular weight of chemical compounds by separating molecular ions according to mass/charge ratio (m/z).

MALDI –Matrix Assisted Laser Desorption Ionization

The protein sample is dissolved in the matrix, and then a laser beam is applied, which results in the ionization of the proteins, which are then analyzed. Charged protein accelerated through evacuated tubes and separated by m/z ratio.

20. Explain the methods which can be used for the scaling up of animal culture.

Ans: Roller bottles

In roller bottles, the cells adhere to the total curved surface area of the micro carrier beads, thereby markedly increasing the available space for growth.
These tissue culture bottles can be used in specialized CO₂ incubators with attachments that rotate the bottles along the long axis.
After each complete rotation of the bottle, the entire cell monolayer has transiently been exposed to the medium.
The volume of medium needs only to be sufficient to provide a shallow covering over the monolayer.

Micro carrier beads

These beads are used to increase the number of adherent cells per flask and are either dextran or glass-based and come in a range of densities and sizes.
The beads are buoyant and therefore can be used with spinner culture flasks.
The surface area available for cell growth on these beads is huge.
Microcarrier beads, when re-suspended at the recommended concentration, provide 0.24 m2 for every 100 ml of culture flask.
Under these conditions, adherent cells can be grown to very high densities before crowding becomes a problem.
Cells growing at such high densities will rapidly exhaust the medium, which may need replacing during culture.

Spinner cultures

Spinner cultures are used for scaling up the production of suspension cells.
They consist of a flat surface glass flask with a suspended central teflon paddle that turns and agitates the medium when placed on a magnetic stirrer.
Commercial versions incorporate one or more side arms for sampling and/or decantation.
The cells are not allowed to settle to the bottom of the flask, and thus, cell crowding occurs only at very high densities.
Stirring the medium improves gas exchange.

21. State any three advantages of using Pichia pastoris as a eukaryotic expression host.

Ans: Advantages of Pichia pastoris as a eukaryotic expression host:

a)Has strong inducible promoters
b) Is capable of making post-translational modifications
c) Downstream processing is simpler as Pichia does not secrete its own proteins into the
fermentation medium

22. How would you detect a specific microbial contamination from a given water sample using PCR? Give a brief explanation of the process.

Ans: Selective amplification of microbial gene (in test water sample) using microbe-specific primers by PCR.

Principle of PCR: Selective Amplification by designing suitable primers to include the sequence that is to be amplified.

It was invented by Kary Mullis.

Basic steps should include

Denaturation: It involves the heating of DNA above 80 degrees Celsius, which results in the breaking of hydrogen bonds present between two strands, resulting in two different individual strands.
Annealing: It involves the hybridization of two primers at the 3’ region of each strand.
Extension/Polymerization – It involves the addition of ddNTP to the 3’ region of each strand with the help of Taq polymerase( DNA Polymerase ), resulting in a complete DNA molecule.

23. Following are a few transgenic crops approved by the U.S.F.D.A. Identify ‘a’, ‘b’ and

‘c’ and complete the table.

Crop	Gene(s) introduced	New/Improved Character	Developer
Canola	a	High laurate oil	Calgene
Corn	EPSP synthase	b	Monsanto
Cotton	Acetolactate synthase	Weed Control	c

Ans:

a)Thioesterase
b)Weed control
c)DuPont

24. Rohan cultured Streptococcus bacteria in his lab to check whether it is gram-positive or gram-negative, and then he threw the culture directly in the dustbin. Is this method of disposal ethically and ecologically safe?

Ans: No.

It may cause infections leading to health problems

Mutations may convert even harmless strains to potentially dangerous ones

25. What are edible vaccines? How are they better than conventional vaccines? Give any two points.

Ans: The genes encoding antigenic proteins can be isolated from pathogens and expressed in plants. Such transgenic plants or their tissues producing antigens can be eaten for vaccination/immunization. These are called edible vaccines.

Edible vaccines offer the following advantages over conventional vaccines. ( Any two)

1. Low cost
2. Alleviation of storage problems
3. Easy delivery system by feeding (any other relevant point)

What are somatic hybrids? How are they produced?

Ans: Plants raised by tissue culture of somatic hybrid cells formed by fusion of plant cell protoplasts are called somatic hybrids.

Procedure: Isolation of plant cell protoplasts and their fusion. Selection of hybrid cells and raising by plant tissue culture

SECTION D

26. What are type II restriction endonucleases? Give an example of a type II restriction endonuclease that generates flush ends and the sequence recognized by it. Explain how they are named. Name any other enzyme and its utility in the cloning experiment.

Ans: R.E. type II recognizes a specific DNA sequence and cuts within the sequence, generating sticky/flush ends. In recombinant DNA technology, we use type II REs as they are highly specific in their action. Alu I with the restriction site 5’ – AGCT’-3 (Make it double-stranded)

Nomenclature: Eco RI with the restriction site 5’-GAATTC-3’ (Make it double-stranded)

Nomenclature with one example

The first letter indicates the genus of the organism
The next two letters indicate the species name.
The next letter indicates the strain name
The next Roman letter indicates the order of discovery.

Eco R I – E indicates the genus” Escherichia”

The next two letters indicate the species “coli” name.
The next letter indicates the strain “Rd “ name
The next Roman letter, i.e., I, indicates the order of discovery
The functions of a) Alkaline phosphatase/ b) DNA ligase.
The role of alkaline phosphatase is to prevent self-re-ligation of the vector /The role of
DNA ligase is used to make a 3’-5’ phosphodiester bond. (Any one)

27. Name the technique developed by O’Farrell. Schematically depict key steps in the 5 separation of proteins using the technique. Highlight the basis of separation at each step.

Ans: 2D – Gel electrophoresis

As two components ( IEF and SDS–PAGE) are carried at right angles to each other, thereby increasing the resolution.

Principle of IEF- The Separation of the proteins is based on their pIs.

Ampholytes (Polyamino-Polycarboxylic acids ) are used in generating the pH gradient.
SDS-PAGE- Separation of the proteins is based on their molecular mass.
Silver stain is used as a staining dye.

Classify protein-based products. Give one example under each category along with its application. How are these useful to the biotechnology industry?

Ans:

i) Blood products and vaccines, e.g., Factor IX for treating hemophilia
ii)Therapeutic antibodies and enzymes, e.g,. Monoclonal antibodies OKT3 for preventing graftness.
iii) Therapeutic hormones and growth factors, e.g., Insulin to treat diabetes.
iv) Regulatory factors, e.g., Interferons for antiviral properties.
v) Analytical applications, e.g., horseradish peroxidase for ELISA.
vi) Industrial enzymes, e.g., Papain for meat tenderization.
vii) Functional non-catalytic proteins, e.g., Kappa casein for milk protein stabilization.
viii) Nutraceutical proteins, eg, Infant food formulation to provide adequate nutrition for infants.

These products are of commercial value to the Biotechnology industry.

(Any five )

28. Explain how the cDNA microarray technique can be used to study cellular response to the environment. Support your answer with a flowchart for the same.

Ans: Cellular response to the environment can be studied by comparing the amounts of many different mRNA in normal and affected cells (eg, Cancerous cells). (Explanation of the preparation of microarray and the cDNA microarray technique)

Major steps involved in comparative microarray hybridization experiments between normal and affected (for example, cancerous cells)

1. Choosing a cell population and extracting mRNA.
2. Reverse transcribing the mRNA to get cDNA.
3. Fluorescent labelling of cDNA.
4. Hybridization to a DNA microarray.
5. Scanning the hybridized array.
6. Interpretation of scanned image.

a) Which information can be retrieved from the following databases?

i)EMBL

ii)PDB

iii)PALI

b)Give two reasons for completely sequencing a genome.

Ans: a)

i) EMBL-Nucleotide sequence
ii) PDB -3D structure of proteins
iii)PALI -Phylogenetic analysis and alignment of proteins

b) Provides a means of discovery of all the genes/ shows relationship between genes/tools for future experimentation/ organizes all genetic information about organisms (Any two points)