Class 12 Biotechnology Sample Question Paper 2016

Class 12 Biotechnology Sample Paper 2016

Time allowed: 3 hours

Maximum Marks: 70

SECTION A

1. A scientist wants to protect a part of a DNA from attack by restriction enzymes. Design the first step of his experiment?

Ans: Methylation. The student will add a methyl group to one or two bases within the sequence recognized by an enzyme.

2. The presence of a selectable marker is an essential feature of an ideal cloning vehicle. Give reasons.

Ans: A gene whose product can identify the host cells containing the vector.

3. 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.

4. Given below is a list of the first 8 residues of the β-helix in myoglobin from different organisms. Based on this information, identify the amino acids which are most

(a) conserved

(b) variable

Ans: (a) 4 & 8 with L & E 1

(b) 7 with five different amino acids

5. In assessing the effect of growth factors on animal cell cultures, a particular phase of growth is more suitable. Name this phase, giving a reason for the same.

Ans: Log Phase. Cell number increases exponentially

6. CHO animal cell line is used to express r-HuEPO. Give a reason.

Ans: CHO is an eukaryotic host cell, so it is used to clone eukaryotic genes.

SECTION-B

7. pUC19 and a linear DNA (both of the same size) have two sites for the same restriction – endonuclease. When cleaved and separated on agarose gel electrophoresis, how many bands will be visualized in each case, and why?

Ans:In pUC19 –two bands

Linear DNA

Because restriction endonuclease cleaves the DNA internally

8. Chymotrypsin catalyses the hydrolysis of proteins containing bulky, aromatic, hydrophobic amino acids. Comment.

Ans: The negatively charged oxygen anion can make a nucleophilic attack on the carbonyl carbon of the peptide bond of its substrate. It loosens the carbonyl carbon, so that a water molecule can hydrolyse the bond.

9. Interpret the possible use of nick translation in detecting chromosomal translocations. Draw a suitable diagram.

Ans: Nick translation is used to detect CML i.e., Chronic Myelogenous Leukemia

10. C.elegans is an eukaryotic organism with a genome of 97 Mb and about 20,000 genes. Why 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 and other eukaryotes.

Yeast encodes 70 percent of proteins, whereas in warm-blooded animals and fruit flies encode 20-25%.

BLAST helps in finding the homology in biological sequence alignment. Give any two reasons for this homology.

Ans: Biological homology can be detected by BLAST- basic local alignment search tool. Homologues represent the similarity due to common ancestry, and they will have the same function.
Paralogs share similarities due to random chance and may differ in function.

11. 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

12. State any two advantages of using Pichia pastoris as a eukaryotic expression host.

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

(i) Has strong inducible promoters
(ii) Is capable of making post-translational modifications
(iii) Downstream processing is simpler as Pichia does not secrete its own proteins into the fermentation medium. (Any two of the above advantages)

13. Execute the engineered biosynthetic pathway, which leads to the production of valuable secondary metabolites for their overproduction.

Ans: Biosynthetic pathway that leads to the production of secondary metabolites are being engineered for their overproduction to reduce the cost. The overexpression of the gene that encodes for the first enzyme in the pathway results in higher levels of desired end products.

14. Enlist the advantages and limitations of animal cell culture (two each).

Ans: Advantages of animal cell culture: Homogeneous genetic population, Controlled physico-chemical environment, Easy to add genes, Available in adequate numbers, Easy production, No ethical clearance required, Cost-effective.

Disadvantages of animal cell culture: Small size, sensitive to detect the changes, challenging scale up, may not represent the in vivo phenotype and genotype.

SECTION-C

15. Parth has identified the luciferase gene from firefly. Construct a flowchart of the steps that you would follow to transfer the gene to a plant.

Ans: Steps of rDNA: Isolation of DNA from firefly

Cut it with a restriction enzyme and, by using a probe, take out the desired gene after electrophoresis
According to the size of the desired DNA, select a vector
Insert the vector in the appropriate host cell
Co-cultivation of the host with explants
Transfer the explants with the desired gene to the culture medium

16. One of the major uses of genome sequencing is to develop tools for future experimentation. Given the sequence of a ribonuclease gene from the model plant Brassica, how would you design a tool for isolating the ribonuclease gene from an Oryza sativa plant?

Ans:

The ribonuclease gene from Brassica is used as a probe.
Then isolate DNA from Oryza
Cut this DNA into fragments
Then isolate DNA fragments by gel electrophoresis
Transfer the assembly to the Nylon membrane
Then use the probe to search the given gene

17. Linus Pauling predicted that ScHb differed in charge from normal hemoglobin protein. Explain the technique that was used to confirm this with the help of a diagram.

Ans: Protein fingerprinting/peptide mapping.

18. If a given protein with a molecular weight of 20,000 daltons containing 5,4,3,2, and 1 charges, is subjected to mass spectrometry, and the sequence of protein ions is detected by the mass spectrometer.

Ans:m/z= M+ nH+/n

m/z=20,005/5=4001 1⁄2

m/z=20,004/4= 5001 1⁄2

m/z=20,003/3=6668 1⁄2

m/z=20,002/2=10,001 1⁄2

m/z=20,001/1=20,001 1⁄2

Sequence—It detects protein ions at m/z=4001, 5001, 6668, 10001, and 20,001, respectively.

19. A patient suffering from blood cancer has been put on radio and chemotherapy for the past 5 months. How can the FISH technique be used to monitor the effect of the same?

Ans: FISH- fluorescent in situ hybridization technique involves introducing fluorescent colours into chromosomes 9 and 22 using nick translation (red in 9 and green in 22) and then counting the number of yellow cells (i.,e having blood cancer) and following their decrease with chemo and radiotherapies.

20. Annotation of human genome sequence reveals that our genome contains 30000-33000 genes. Proteomic analysis indicates that human cells are capable of synthesizing more than 30,000 different proteins. How can this discrepancy be reconciled?

Ans:

There is a non-linear relationship between the number of genes and proteins

21. If a culture of Haemophilus contains 105 cells/ml at 4:00 a.m. and 1011 cells/ml at 4:00 p.m., calculate its specific growth rate and doubling time. Which growth phase does this bacterial culture show maximum specific growth rate?

Ans:

Specific growth rate- 1.1515 hr-1
Doubling time- 0.693/1.1515=0.6 hours=36 minutes
Exponential phase

22. 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. 1.

It may cause infections leading to health problems. (Mutations may convert even harmless strains to potentially dangerous ones).

Cleanliness is the primary responsibility of every citizen.

23. Somatic hybrids and cybrids are produced by a technique of plant biotechnology. Identify this technique and explain by citing two examples of plants.

Ans: Somatic cell hybridization/ parasexual hybridization.

The first interspecific hybrid was developed between Nicotiana glauca and Nicotiana langsdorfii in 1972.
First intergeneric hybrid developed between Solanum tuberosum and Lycopersicon esculentum, and the hybrids are known as ‘Pomatoes or Topatoes’

Though a genetically engineered crop is herbicide and pesticide-resistant, it still requires the use of agrochemicals. Mention at least three facts to justify the statement.

Ans: Herbicides and other chemicals affect the crops, which can be resolved by introducing modified gene for the overproduction of the herbicide target enzyme. This enzyme is expressed in the chloroplasts of plants. So that it becomes insensitive to the herbicide

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

Ans:

25. Monoclonal antibodies are preferred over polyclonal antibodies for diagnostics and antibody-based therapy. Justify giving two reasons for the same by taking Herceptin as an example.

Ans: Monoclonal antibodies are specific to a single epitope of the antigen, due to which the results obtained by using them are clear-cut.

Herceptin is a targeted therapy of HER 2+, i.e., Human epidermal growth factor Receptor-2 positive.

And used for the treatment of early-stage breast cancer.

SECTION-D

26. PCR allows for rapid and highly specific diagnosis of infectious diseases. Enumerate the basic steps of polymerase chain reaction (PCR). How can we selectively amplify a DNA fragment? Mention any two applications of PCR.

Ans: Basic steps include:

Denaturation
Annealing
Extension/Polymerization

Selectively amplify by designing suitable primers to include the sequence that is to be amplified.

Any two of the following applications:

-DNA fingerprinting/Forensic Science
-Detection of infective agents
-Identification of genetic diseases

Distinguish between:

(i) dNTP & ddNTP
(ii) pBR322 & pUC19
(iii) M-13 & lambda phage
(iv) Cosmid & plasmid
(v) Transformation and transfection

Ans:

(i) dNTP & ddNTP
- dNTP used in DNA replication
- ddNTP used in chain termination
- Structural differences can also be shown
(ii) pBR322 & pUC19
- pBR322 contains two antibiotic-resistant genes
- pUC19- contains MCS 1⁄2
(iii) M-13 & lambda phage
- M-13: Circular and single-stranded
- Lambda phage: Linear double-stranded
(iv) Cosmid & plasmid
- Cosmid: having features of a plasmid and the cos sites of phage lambda
- Plasmid: small, circular, extra-chromosomal, self-replicating, naturally present in bacteria
(v) Transformation and transfection
- Transformation: Cold CaCl₂-treated competent bacterial cells to introduce rDNA
- Transfection: Transfer rDNA into host cells by mixing foreign DNA with charged substances like calcium liposomes/calcium phosphate/DEAE dextran.

27. We often find catchy slogans in laundry detergents, with biologically active enzymes.

(i) Identify this enzyme.
(ii) Name the residues that contributed to its enzymatic activity.
(iii) The native form of this enzyme is inactivated by bleach. Give a reason.
(iv) Is there any way to retain the activity even in the presence of bleach?

Ans:

(i) Subtilisin
(ii) Residues are Ser 221, His 64, and Asp 32
(iii) Oxidation of the amino acid Methionine at position 222
(iv) Substitution of Met 222 by Ala using site-directed mutagenesis

Give reasons for the following:

(i) OKT-3 is used to prevent graft rejection following kidney transplantation.
(ii) Kappa casein is involved in micelle stabilization of milk proteins.
(iii)Whey protein detoxifies xenobiotics.
(iv) Curd is used as a probiotic.
(v) BCAA-enriched food is taken before and after exercise.

Ans:

(i) OKT-3 is monab-CD3, an immunosuppressant drug given intravenously to reverse acute rejection. 1
(ii) Kappa casein contains a lipid molecule. 2/3 of the protein is hydrophobic
(iii) Whey protein results in the elevation of a tripeptide glutathione in cells, which detoxifies xenobiotics. 1
(iv) Curd is a good source of beneficial bacteria that can colonise the intestinal tract.
(v) BCAA is an essential for the biosynthesis of muscle proteins as its carbon part is used as fuel, and nitrogen is converted into Alanine, which changes into glucose in the liver.

28. Depict the induction of crown gall on a stem of a plant by Agrobacterium tumefaciens with the help of a schematic diagram.

Ans:

Outline various steps involved in the regeneration of whole plants using culture techniques.

Ans: