In This Post we are providing Chapter- 12 BIOTECHNOLOGY AND ITS APPLICATION NCERT MOST IMPORTANT QUESTIONS for Class 12 BIOLOGY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter
NCERT MOST IMPORTANT QUESTIONS ON BIOTECHNOLOGY AND ITS APPLICATION
1.Describe how nematode – resistant transgenic plants have been obtained?
Ans.A nematode Meloidogyne incognita infects tobacco plant &reduces its yield. The specific genes fromparasite are introduced into plant using Agrobacterium. The genes are introduced in such a way that bothsense& Antisense RNA are produced. Since these two RNAs are complementary, they form a doublestranded RNA (ds RNA). This neutralizes the specific RNA of nematode by a process called RNAinterference as a result, the parasite cannot live in transgenic host & plant is protected from the pest.
2.What are Cry proteins? Name an organism that produces it. How has man exploited this protein to his benefit?
Ans.The soil bacterium Bacillus thuringiensis produces crystal proteins called cry proteins that are toxicto larvae of insects like tobacco budworm, beetles & mosquitoes. The cry proteins exist as inactiveprotoxin& gets converted into active toxin when ingested lay the insect, as the alkaline pH of gutSolublises the crystal. The activated toxia binds to surface of epithelial cells ofmidgut& create pores thiscauseslysis of cells leading to death of insects.The genes encoding this protein are isolated from bacterium & incorporated into crop-plant to make them insect – resistant.
3.Write an account on the production of human insulin in transgenic organisms.
Ans. Human insulin consists of two short polypeptide chains: chain A & B linked by disulfide bonds.Insulin is secreted as prohormone which has to be processed before it becomes a mature & functionalhormone. The prohormone contains another polypeptides called C-peptide which is removed during
maturation.Using genetic engineering, the two DNA sequences coding for chains A & B of human insulin areintroduced into plasmid of E – coli – to produce insulin. The two chains produced are extracted &combinedby creating disulfide bridges.
4.Compare & contrast the advantages & disadvantage of production of Genetically modified organisms?
Ans. ADVANTAGES OF PRODUCING GMOS.
- GM crops produce desired phenotypic traits in crop plants.
- The genes responsible for production of specific proteins are inserted into GM crops. These crops then produce that specific protein.
- Transgenic crops synthesizes new end product of specific biochemical pathway.
- These crops also help in preventing expression of existing native Gene.
DISADVANTAGES OF PRODUCING GMOS:
- Transgenic crops may endanger wild & native species.
- GM crops may cause health problems by supplying allergens.
- GM crops may damage to the natural environment.
5.What is RNA Silencing? How is this strategy used to create pest – resistant plants?
Ans.RNA silencing is a technique which involves silencing or disabling of specific mRNA due tocomplementary ds RNA molecule that binds to & prevent translation of mRNA. This strategy is used toprevent infection of roots of tobacco plants lay nematode Meloidegyne incognita. In this strategy, complementary ds RNA is produced against specific mRNA. The source of this complementary RNA couldbe from an infection by viruses having RNA genomes. Using Agrobacterium vector nematode specificgenes were introduced into host plant. The introduction of DNA was such that it produced both sense &anti-dense RNA in the host cell. These two RNA’s being complementary to each other formed a doublestrand RNA that initiated RNAi& thus silenced specific mRNA of the nematode. The consequence wasthat parasite could not survive in transgenic host.
6.What are the steps involved in synthesis of genetically engineered insulin.
Ans. Steps involved in Insulin production are :-
- for synthesis of Insulin, RNA is extracted from β−β−cells of islets of Langehans of pancreas.
- With the help of enzyme Reverse transcriptase, single stranded DNA complementary to mRNA is synthesized second strand of DNA complementary to first is synthesized with enzyme DNA polymerase.
- The two strands of copy DNA is joined to plasmid by using an enzyme called terminal transferase.
- The two ends of DNA get annealed by enzyme called ligase thus ends of inserted DNA & plasmid are sealed & a new circular plasmid is formed. This is a molecule of recombinant DNA.
- This recombinant DNA is then inoculated in a new bacterial cell of E-coli & inserted in a bacterial gene after having cut by restriction enzyme.
- After proper expression of genes the bacterial cells of both cultures are lysed with appropriate chemicals. The fragments of insulin are then separated from enzyme by cyanogen bromide.
7. The clinical gene therapy is given to a 4 years old patient for an enzyme which is crucial for the immune system to function.
Observe the therapeutical flow chart and give the answer of the following:
(a) Complete the missing steps (B) and (D)
(b) Identify the disease to be cured.
(c) Why the above method is not a complete solution to the problem?
(d) Scientists have developed a method to cure this disease permanently. How?
Ans. (a) Step (B) : Lymphocytes are grown in culture medium. Step (D) : Infusion of genetically engineered lymphocytes into patients.
(b) Adenosine deaminase (ADA) deficiency.
(c) As genetically engineered lymphocytes are not immortal, the patient requires periodic
infusion of cells.
(d) If the gene isolated from bone marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure.
8. In the given figure, Agrobacterium is utilized for the production of a transgenic crop. Explain the steps a, b, c, d and e shown in the figure.
Ans. Step (a) Plasmid is removed and cut open with restriction endonuclease.
Step (b) Gene of interest is isolated from another organism and amplified using PCR
Step (c) New gene is inserted into plasmid
Step (d) Plasmid is put back into Agrobacterium
Step (e) Agrobacterium based transformation.
9. In the given figure, Form (A) and Form (B) represents different forms of a proteinaceous hormone secreted by pancreas in mammals.
(a) What type of bonding is present between chains of this hormone?
(b) What are these form (A) and form (B). How these forms differ from each other?
(c) Explain how was this hormone produced by Eli Lilly, an American company, using rDNA technology.
Ans. (a) Disulphide bonds
(b) Form (A) – Proinsulin
Form (B) – Mature insulin.Proinsulin contains an extra stretch called C peptide which is absent in mature insulin.
(c) Eli Lilly company prepared two DNA sequences corresponding to A and B peptide chains of human insulin and introduced them in plasmid E. coli to produce insulin chains. Chains A and B were producedseparately, extracted and combined by creating disulphide bonds to form insulin.
10.What is Gene therapy – Illustrate using example of Adenosine deaminase deficiency?
Ans.Gene therapy is a collection of methods that allows correction of a gene defect. In this method,genes are inserted into the cells & tissues of an individual to correct certain hereditary diseases. Itinvolves delivery of a normal gene into the individual or embryo to replace the defective mutant allele of the gene. Viruses which attack the host cell & introduce genetic material into host are usedas vectors.
For example Adenosine deaminase (ADA) deficiency can be cured by bone marrow transplantation in some children but is not curative for Gene therapy, lymphocytes are grown in a culture & functional ADA, cDNA is introduced into these lymphocytes. These lymphocytes are then transferred into body of patient the patient requires infusion of such genetically engineered lymphocytes.
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