Class 12 Biotechnology Sample Question Paper 2017

Class 12 Biotechnology Sample Paper 2017

Time allowed: 3 hours

Maximum Marks: 70

Section A

1. How is oxygen provided in fermentors? 1

Ans: Sparging / forced aeration

2. Why is a pilot plant essential in microbial culture work? 1

Ans: A mini version of the commercial plant is essential to validate lab processes on an intermediate scale before attempting commercial production

3. As a biotechnologist, what would you suggest to a farmer for successful pollination or fertilization in plants?

Ans: To utilize the barnase/ barstar system

4. Why do plant cells in culture require nutrient media for growth? 1

Ans: Plant cells in culture cannot perform photosynthesis

5. Why is the splitting of animal cells essential? 1

Ans: To periodically provide fresh nutrients and growing space to cells

6. Name the first drug to be produced by mammalian cell culture. 1

Ans: tPA / Tissue plasminogen activator

Section B

7. Which type of restriction enzymes are used in RDT and why? 2

Ans: Type II restriction enzymes are used because they can recognise and cut specific cleavage

sites in palindromic sequences

8. Explain in brief any two types of non-covalent interactions found in proteins.

Ans: Ionic bonds

Ionic bonds: These involve interactions between the oppositely charged groups of a molecule. For example, the positively charged amino acid side chains of lysine and arginine can form salt bridges with the negatively charged side chains of aspartate and glutamate. These ionic interactions are also known as salt bridges because they are dominant bonds found in salts like sodium chloride, wherein the positively charged sodium ion interacts with the negatively charged chloride ion.
Hydrogen bonds: Hydrogen bonds are formed by “sharing” of a hydrogen atom between two electronegative atoms, such as Nitrogen and Oxygen. In this case, strongly polarised bonds between hydrogen and a small, very electronegative atom (N, O, or F) allow a strong dipole-dipole bond to be formed with another small, very electronegative element (N, O, or F). Importantly, the very small sizes of these elements also allow them to approach each other so closely that a partial covalent bond is also formed (e.g,. O-H—N).
Van der Waals forces: These forces are weak attractions (or repulsions) that occur between atoms at close range. The Van der Waals types of forces are essentially contact forces, proportional to the surface areas in contact. Even though weak, these bonds can be important in macromolecules because the large surface areas involved can result in reasonably large total forces.
Hydrophobic interactions: Hydrophobic interactions can be best explained by taking the example of oil in water. The oil tends to separate out fairly quickly because the water forces it out. The hydrophobic interaction is thus a manifestation of the hydrogen bonding network in water. In water, each molecule is potentially bonded to four other molecules through H-bonds.

9. Which type of DNA library would you prefer for liver cells? Give a proper explanation for making such a library.

Ans: c DNA library would be preferred.

mRNA molecules are highly unstable as they are easily degraded by RNases. Therefore, mRNA molecules are copied into the more stable DNA (now called cDNA) before cloning. The construction of a cDNA library begins with the isolation of mRNA from a given cell type or tissue, which is copied into cDNA using a special enzyme called reverse transcriptase. The procedure results in double-stranded cDNA, which can be incorporated into vectors such as pBR322.These recombinant vectors are transformed into host bacterial cells, eg, E. coli. This forms a cDNA library.

10. 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, which may denature the protein
v) Minimize processing time

11. The number of genes is not related to the complexity of an organism. Give reasons.

Ans: Due to the existence of overlapping genes, splice variants, post-translational, and post

transcriptional modifications

12. Calculate the generation time of a bacterial population in which the number of bacteria increases from 104/ml to 107/ml during four hours of exponential growth.

Ans: u = 2.303(log Xt – log X0)/t

u = 2.303(log X_t – log X₀)/4

(X₀ = 10⁴, X_t = 10⁷, t= 4 hours)

Solving the above equation by using the values, we get,

u = 1.73/hr

t_d = 0.693/1.73= 0.4 hrs

0.4×60 = 24 mins

n = 3.3 (Log 10 – Log 10 )

= 3.3 (7 – 4) = 10

t = 240 minutes / 10 d = 24 minutes

13. The Ti plasmid vector of Agrobacterium tumefaciens is disarmed. Where is the gene of interest incorporated into the Ti plasmid?

Ans: Ti plasmid vectors are disarmed because they do not require any chemical or equipment to transfer the gene of interest into plant cells. The gene of interest is incorporated in the T-DNA region of the Ti plasmid.

14. Why are serum and antibiotics essential as growth supplements for animal cells in culture?

Ans: Serum is a source of various amino acids, hormones, lipids, vitamins, polyamines, and salts containing various ions. Serum also contains growth factors required for the proliferation and attachment of animal cells to culture vessels. Antibiotics control the growth of bacterial and fungal contaminants.

Section C

15. How are pUC 19 vectors used for the selection of recombinants? 3

Ans: Insertional inactivation of the Lac Z gene leads to suppression of its activity. This ensures selection of recombinant cells, which appear white, from non-recombinant cells, which appear blue ( Blue-White selection).

16. Yeast cells have been transformed with the Yep vector containing our gene of interest. How would you select the recombinants over cells not containing the plasmid?

Ans: Yep contains the LEU 2 gene, which codes for an enzyme required for the synthesis of the amino acid leucine. Recombinant yeast cells will grow on a medium lacking leucine and hence can be selected over cells not containing the plasmid (which cannot grow on such a medium).

17. Describe the principle of the MALDI technique. Write its two main uses of protein studies.

Ans: A popular method called Matrix Assisted Laser Desorption Ionisation (MALDI) is used to volatilize and protonate peptides and proteins. In this procedure, the sample is transferred from a condensed phase to a gas phase with the help of a solid matrix. This technique determines the molecular weight of proteins by separating molecular ions according to their mass/charge ratio.

Uses: To obtain protein structural information, such as peptide mass or amino acid sequences. To identify the type and location of amino acid modification within proteins.

What are the principles behind isoelectric focusing and SDS PAGE techniques? Why is 2D electrophoresis better than single-dimensional electrophoresis?

Ans:

Principle of IEF: Separation of proteins based on their different pI values.
Principle of SDS PAGE: Separation of proteins based on their size.

2D electrophoresis is better because proteins are separated into 2D patterns with high resolution based on charge and size.

18. How is an extracellular protein purified from a fermentation medium? Illustrate the steps with a flowchart.

Ans: Steps in a flowchart

19. What are SNPs?Explain the relevance of studying these, citing any two of their important applications.

Ans: SNPs or single-nucleotide polymorphisms are common variants in DNA that can have any one of the four DNA bases (A, T, G, C) at a single site, so that different individuals may have different bases at these positions.

Relevance of studying SNPs using any 2 of the following applications:

1. DNA fingerprinting
2. Medicine
3. Population genetics
4. Ancestral relationships

20. Graphically differentiate between fed batch and continuous cultures. Which type of culture system is most suitable for obtaining the maximum amount of cellular products?

Ans:

Fed Batch Culture and Continuous Culture.

Continuous culture is suitable for obtaining the maximum amount of cellular products.

21. 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 as 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. The clones expressing novel molecules or molecules with improved characteristics are used for large-scale production by fermentation techniques.

22. 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:

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

23. What are somatic hybrids? How are they produced? 3

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

24. Give a brief outline of the technique for the production of monoclonal antibodies. Why are monoclonal antibodies preferred over serum antibodies in diagnostics and therapeutics?

Ans: In Hybridoma technology, mAbs are produced by fusing antigen-activated B lymphocytes that have been immortalised with myeloma cells using polyethylene glycol. This technique was developed by Cesar Milstein and George Kohler (Nobel Prize winners). The hybrid cells retain the ability of B cells to secrete antibodies and the ability of myeloma cells to grow indefinitely. The hybrid clones, when grown in culture, produce epitope-specific mAb.

Antibodies bind to specific domains of antigens known as epitopes. The antibodies present in serum are a heterologous population released by different populations of B-lymphocytes and therefore are known as polyclonal antibodies. The polyclonal antibodies can bind to related epitopes and therefore do not give accurate results in diagnostics. Monoclonal antibodies (mAbs), on the other hand, bind specifically to an epitope on an antigen and therefore are useful in detecting specific antigens (diagnostics) or blocking their binding by other molecules. Monoclonal antibodies provide accurate results and are therefore used in diagnostics.

Hybridoma technology has revolutionised the area of diagnostics and antibody-based therapies. The availability of monoclonal antibodies has helped in the early detection of many infectious diseases like hepatitis and AIDS.

25. How would you scale up kidney cells grown in culture? 3

Ans: Kidney cells are anchorage-dependent. Hence, scale-up is done by culturing the kidney cells using roller bottles with microcarrier beads. The culture bottles are kept in CO2 incubators for the growth of cells. This system largely increases the surface area for the growth of anchorage-dependent animal cells, and therefore scale-up of cultured animal cells is achieved.

Section D

26. Give reasons for the following:

a) A BCAA-enriched diet is recommended to athletes before and after exercise.

b) Give the scientific relevance of the usefulness of whey.

Ans: (a) BCAA are essential for the biosynthesis of muscle proteins/ help in anabolic muscle

building activity/protect existing muscle mass/reduce muscle breakdown/act as an energy source/carbon part is used as fuel and nitrogen part is used to make alanine, which turns into glucose in the liver.

(b) Whey is used to cure a spectrum of illnesses like jaundice, infected skin lesions, and urinary tract infections. Whey protein results in the elevation of tripeptide glutathione in cells, which helps in the detoxification of xenobiotics and protects cells from the action of free radicals.

27. Why do ddNTPs cause chain termination during Sanger’s DNA sequencing method? Write the DNA fragments formed by chain termination for the given original DNA strand. 3’ATGCTAGC 5’.

Ans: 3’OH group is absent in ddNTP’s which causes termination of the growing DNA chain during Sanger’s DNA sequencing method.

DNA fragments formed by chain termination in all four tubes for the given strand. 3’ATGCTAGC 5’

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. Brief explanation of the process with the PCR technique.

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.

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).