Class 12 Biotechnology PYQ 2019 Solved
Time allowed: 3 hours
Maximum Marks: 70
SECTION A
1. What is the function of reverse transcriptase enzyme?
Converts mRNA into cDNA
OR
What is the advantage of using polylinker in a vector?
Polylinker provides flexibility in the choice and use of restriction enzymes.
2. Why is macerozyme used in obtaining cell suspension culture from plant tissue?
Macerozyme dissolves the middle lamella between the cells to release single cells.
OR
Name the hormone involved in fruit ripening.
Ethylene Gas
3. What does IUPAC single-letter code ‘R’ stand for?
Purine/ G or A/Arginine
4. What is lipofection?
Transfer of rDNA into host cells, using charged substances like cationic liposomes.
5. If the specific growth requirements of an isolated strain of bacterium are not known, which type of medium should be used to grow (culture) the same?
Complex medium/ Luria Broth/ Nutrient Broth/ Trypticase Soy Broth.
6. Which type of non-covalent interaction, through a weak attraction force, is important in biomolecules?
Van der Waals Forces
SECTION B
7. How does nerve gas cause death in humans?
Nerve gas alkylates active serine in the brain enzyme acetyl choline esterase, inactivating it and leading to death.
8. Differentiate between primary and secondary metabolites in plants, with one example of each.
| Primary Metabolites | Secondary Metabolites |
| Chemicals that are required for plant basic metabolic processes. | Eg. sugars, lipids, amino acids, nucleic acids. |
| Eg. sugars, lipids, amino acids, nucleic acid. | Function is not clear but they are used in a defense mechanism against pests and pathogens. |
OR
Inter-generic crosses hardly lead to successful production of hybrids. Why?
Intergeneric crosses are between distantly related plants, which result in abnormal development of the endosperm causing premature death of embryo.
9. How was ‘Golden Rice’, a transgenic plant, developed using genetic engineering techniques?
Golden Rice was developed by introducing three genes involved in the biosynthetic pathway for carotenoid under the control of endosperm-specific promoter, so that the gene products (enzymes) are synthesized in the rice endosperm.
10. OKT-3 can help in preventing transplant rejection. How?
OKT3 acts by blocking the function of T-cells by binding to the CD3 cell surface receptors. After OKT3 therapy is over, T cell function usually returns to normal within a week.
OR
How can tPA prevent heart attack?
tPA is a serine protease that catalyzes the conversion of plasminogen to plasmin, which is responsible for dissolving blood clots.
11. Maintenance of extracellular and intra-cellular pH is essential for survival of mammalian cells in culture. Why?
Optimum pH is important for maintaining appropriate ion balance, maintaining optimal function of cellular enzymes and for optimal binding of hormones and growth factors to cell surface receptors. Even transient changes in pH can alter cell metabolism, which can lead to cell death.
12. You are given a sequence without label. How will you find out if it is a DNA or RNA or a protein sequence?
Programs scan the first 20 symbols. If the symbols switch between A, T, G, C, then it is DNA. If instead of T we have U, then it is an RNA sequence. If the symbols switch between more than 4 to 6 letters, then it is a protein sequence.
13. A protein with molecular weight of 20,000 D contains 5 and 4 charges. At what m/z are protein ions detected by the mass spectrometer?
[M+nH]n+
[M+5H]5+ m/z = 20005/5 = 4001
[M+4H]4+ m/z = 20004/4 = 5001
14. In a given genome sequence, the relationship between number of genes and number of proteins is not linear. Why? Give two reasons.
- Post-transcriptional modification, like polyadenylation / mRNA editing. This could lead to the generation of various proteins from a single gene.
- Proteins, after synthesis, could undergo post-translational modifications.
OR
How are DNA chips useful in functional genomics?
DNA chips monitor the whole genome on a single chip so that researchers can have a better picture of the interactions among thousands of genes simultaneously.
SECTION C
15. Detergents nowadays are provided with ‘biologically active enzymes’.
(a) Name the enzyme commonly used.
(b) Why is this enzyme inactivated in the presence of bleach?
(c) How is the engineered enzyme different from its natural form?
- Subtilisin
- Due to the oxidation of methionine at position 222.
- The engineered enzyme has alanine in place of methionine at position 222.
16. Draw a flow chart to show the various steps used for the isolation of recombinant insulin (Humulin) produced in E. coli.
OR
What are the main concerns for the safety aspects related to microbial biotechnology?
The main areas of consideration for safety aspects specific to biotechnology are:
- Potential of genetically modified organisms (GMOs) or recombinant strains to infect humans, animals, and plants to cause diseases.
- Toxicity and allergy are associated with the use of microbially produced biomolecules, especially the recombinant molecules.
- Other medically relevant implications like increasing the environmental pool of antibiotic-resistant microorganisms or the 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.
17. How does metagenomics approach help scientists to identify the novel gene products present in the environment?
- Metagenomics gives scientists an opportunity to cast a wider net on microbial resources present in the environment to fish out genes of their interest.
- It also allows them to analyze the genomes of the microbes without culturing them in the laboratory.
- It is really a very useful approach to study those microbes, which are difficult to culture in the laboratory or have never been cultured in the laboratory as yet, and analyze these to see if they carry any genes that may be exploited for human use.
18. Differentiate between Batch and Continuous culture.
| Batch Culture | Continuous Culture |
| 1. None of the nutrients are limited. | 3 . Maximum Cell density and yield of products are achieved. |
| 2. All phases of growth can be seen | 1. None of the nutrients is limited. |
| 3. Maximum Cell density is achieved. | 1. One nutrient in the medium is limited. |
| 4. Closed culture | 4. Open culture |
Any three points
OR
(a) Why are fermentors provided with baffles?
(b) Foaming of (in) medium can hinder microbial growth. Why?
(c) Microbial strains are usually exposed to chemicals like NTG (Nitrosoguanidine). Why?
- Aeration /to improve oxygen transfer
- Provides a hindrance to the diffusion of air and the denaturation of protein.
- For mutagenesis to generate mutants for strain selection
19. Describe aqueous two-phase partition process for separation of proteins.
- Crude homogenate(cell) added to a biphasic mixture of dextran and PEG.
- PEG is a soluble constituent of cell homogenate.
- Dextran is cellular debris, nucleic acid by nucleases, and lipid by using glass wool.
20. With an example, show
(a) blunt-end cutter restriction enzyme.
(b) sticky-end cutter restriction enzyme.
Which one of the ends are better for directional gene cloning and why?
(a)
- 5’ A G 🠛C T 3’ Blunt End – Alu I
- 5’ T C 🠙G A 5’
(b)
- 5’ G🠛 A A T T C 3’ Sticky End- EcoR I
- 5’ C T T A A🠙 G 5’
Sticky ends can base pair and help ligation.
21. Draw a labelled diagram showing the technique which can be used to identify and locate a specific sequence in a DNA gel using a probe.
Southern Hybridisation technique
OR
Draw a diagram to show and compare the features of pBR 322 and YEp. Why is YEp called a shuttle vector ?
As YEp can be propagated in both prokaryotic (E. coli) and eukaryotic (Yeast) hosts, it is called a shuttle vector.
22. Describe any three methods used to introduce recombinant DNA into the host cells.
(Explanation of any three)
- Transformation: In rDNA technology, the most common method to introduce rDNA into living cells is called transformation. In this procedure, bacterial cells take up DNA from the surrounding environment. Many host cell organisms, such as E. coli, yeast, and mammalian cells, do not readily take up foreign DNA and have to be chemically treated to become competent to do so. In 1970, Mandel and Higa found that E. coli cells become markedly competent to take up external DNA when suspended briefly in cold calcium chloride solution.
- Transfection: Another method to transfer rDNA into host cells involves mixing the foreign DNA with charged substances like calcium phosphate, cationic liposomes, or DEAE dextran and overlaying it on recipient host cells. Host cells take up the DNA in a process called transfection.
- Electroporation: An electric current is used to create transient microscopic pores in the recipient host cell membrane allowing rDNA to enter.
- Microinjection: Exogenous DNA can also be introduced directly into animal and plant cells without the use of eukaryotic vectors. In the procedure of microinjection, foreign DNA is directly injected into recipient cells using a fine microsyringe under a phase contrast microscope to aid vision.
- Biolistics: A remarkable method that has been developed to introduce foreign DNA into mainly plant cells is by using a gene or particle gun. Microscopic particles of gold or tungsten are coated with the DNA of interest and bombarded onto cells with a device much like a particle gun. Hence, the term biolistics is used.
23. Define the terms: RefSeq, Homologues, and Paralogs
- Ref Seq: Ref Seq is a curated database of mRNA and proteins of humans, mice, and rats.
- Homologues: Similarity due to common ancestry and have the same function.
- Paralogs: Duplicated Genes within a genome may have similarities but may differ in function.
OR
What is BLAST? Write the principles that underlie BLAST search.
BLAST: Basic Local Alignment Search Tool
A given sequence is compared with sequences in databases. Top scoring matches are ranked accordingly to set criteria that serve to distinguish between similarity due to ancestral relationships or due to random chance. True matches are further examined thoroughly with other details accessible through ENTREZ and other tools.
24. Name any three databases for Bioinformatics and the information available in them.
| Database | Information available |
| EMBL (European Molecular Biology Laboratory) | Nucleotide sequence |
| UniProtKB | Annotated protein sequence |
| PDB (Protein Database) | Ribosomal RNA database |
| Ribosomal RNAdatabase | Three-dimensional structure of proteins |
| PALI database | Phylogenetic analysis and alignment of proteins |
25. Why are genes difficult to count, even if we know where the genes are in a given genome? Write any three reasons.
Due to the presence of overlapping genes, splice variants, repeated sequences, and gaps between genomes, it is difficult to count the genes. The number of genes is not related to the complexity of organisms.
SECTION D
26. (a) What are stem cells?
(b) Differentiate between pluripotent and multipotent stem cells.
Which of these act as repair system for the body and how?
(c) Give three applications of stem cells in the field of medicine.
- Stem cells are characterized by their ability to renew themselves through mitotic cell division and differentiate into a diverse range of specialized cell types.
- Embryonic cells isolated from the inner cell mass of blastocysts are called pluripotent cells. The adult stem cells found in adult tissues are multipotent cells.
Multipotent cells can act as a repair system for the body by maintaining normal turnover of regenerative organs like blood, skin, etc.
(c) The stem cells are useful in many medical conditions where cells are either dead or injured or abnormal, such as:
- Leukemia (cancerous blood cells).
- Heart disease, heart attack (cardiac tissue damage).
- Paralysis (spinal cord injury).
- Alzheimer’s, Parkinson’s, Huntington’s (dead brain cells).
- Burns (damaged skin cells).
OR
(a) What is a ‘gene knockout’?
(b) Why are mouse models prepared using gene knockouts useful?
(c) Who developed the technique to grow Human Embryonic Stem Cells (hESCs) in culture, and what is the source of these cells?
- Gene knockout is the process of selectively removing a gene.
- Used to understand the genetic basis of diseases, new diagnostic and therapeutic modalities.
- James Thomson; From the inner cell mass of the blastocyst.
27. Explain how the desired genes are introduced in plants using vector-mediated gene transfer. Draw diagram. How can one differentiate between the transgenic and non-transgenic plant ?
Desired genes are introduced in plants by these steps.
- Collect leaf disc/embryo callus
- Infect with disarmed Ti containing Agrobacterium
- Infected Tissue cultured on shoot regeneration medium for 2-3 days to transfer T-DNA along with foreign gene.
- Transformed tissue, transfer to selection cum plant regeneration medium having lethal concentration of kanamycin.
- After 3-5 weeks, regenerated transformed shoot are transferred to root inducing medium.
- After another 3-4 weeks complete plants are transferred to field for hardening.
Transgenic and non-transgenic plants can be differentiated by looking for the desired trait in the transgenic plant (morphological or DNA marker).
OR
(a) How are edible vaccines produced?
(b) Edible vaccines have advantages over recombinant vaccines produced by bacteria. List any three advantages. 2+3=5
Edible vaccines are transgenic plants that have genes encoding for the antigenic proteins isolated from pathogens expressed in plants. Such transgenic plants such as fruits which can be eaten raw. The advantages of these edible vaccines are: (Any three)
- No storage problem
- Easy Delivery System
- Low Cost
- Painless Delivery System
28.
(a) What are nutraceutical proteins?
(b) Curd has been used as a probiotic. Why?
(c) Whey protein can treat a spectrum of diseases. Explain.
(d) In which food system is the water-binding property of whey protein used?
- Nutraceuticals are proteins that have nutritive and pharmaceutical value.
- Curd is a good source of beneficial bacteria and helps in Intestinal function.
- Whey protein elevates the tripeptide glutathione, which can treat a spectrum of illnesses.
- Meat, sausages, cake, and bread (any 1)
