In This Post we are providing Chapter-11 BIOTECHNOLOGY: PRINCIPLES AND PROCESSESS 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: PRINCIPLES AND PROCESSESS
1. Observe the given sequence of nitrogenous bases on a DNA fragment and answer the following question
5´ – CAGAATTCTTA – 3´
3´ – GTCTTAAGAAT – 5´
(a) Name a restriction enzme which can recognise this DNA sequence.
(b) Write the sequence after digestion.
(c) Why are the ends generated after digestion called sticky ends?
Ans. (a) EcoRI
(c) These are named sticky ends, because they form hydrogen bonds with their complementary cut parts.
2. A selectable marker is used in the section of recombinants on the basis of their ability to produce colour in presence of chromogenic substrate.
(a) Mention the name of mechanism involved.
(b) Which enzyme is involved in production of colour?
(c) How is it advantageous over using antibiotic resistant gene as a selectable marker?
Ans. (a) Insertional inactivation
(b) b-galactosidase.
(c) Selection of recombinants due to inactivation of antibiotics requires simultaneous plating on two plates having different antibiotics.
3.Mention the important properties which a good vector must possess?
Ans.The important properties which a good vector must possess are :-
i) Size :- The vector must have small size so that it is easier to purify & isolate.
ii) Origin of replication :- This is a sequence of base pairs where replication starts. Any piece of DNA linked to this sequence can be made to replicate within its host cell & thus, controls the copy number of linked DNA.
iii) Selectable Marker :- A marker is a gene which helps in selecting those host cells which contain the vector & eliminating the non – transformants Common Selectable marker include gene encoding resistance to antibiotics.
iv) Cloning Sites :- The vector Should have a few or at least one unique recognition site to link the foreign / alien DNA. Presence of a particular recognition site enables the particular restriction enzyme to cut the vector.
4.Describe any three vectors less method of introducing the rDNA into a competent host cell?
Ans. i) Transformation :- In order to force bacteria to take up the plasmid, the bacterial cell must first be made competent to take up DNA. This is done by treating them with specific concentration of divalent cationeg. Ca2+ which increases the efficiency with which DNA enters the bacterium through pores in its cell wall Recombinant DNA can then be forced into such cells by incubating the cells with recombinant DNA on ice, followed by placing them at 420 C& then putting them back into ice. This enables the bacteria to take up the recombinant DNA.
ii) Microinjection :- recombinant DNA is directly injected into the nucleus of an animal cell using a micro – needle of tip with diameter (~ 4mm)
iii) Biolistics / Gene gun :- cells are bombarded with high velocity micro – particles of gold or tungsten coated with DNA.
5.Why is Agrobacterium mediated genetic transformation described as Natural Genetic engineering in plants?
Ans.Agrobacterium tumefacien, anatural pathogen of Several dicot plants is able to deliver a piece of DNA known as “t – DNA” to transform normal plant cell into a tumor & direct gene transfer transform tumor cells to produce chemicals required by pathogen . The tumor inducing (Ti) plasmid of
Agrobacterium tumefacien has now been modified into a cloning vector which is no more pathogenic to plant but is still able to use the mechanism to deliver genes of our interest into a variety of plants Since Agrobacterium tumefacien has the natural ability to donate a part of its DNA to the plant during infection. This property of Agrobacterium is exploited and a gene of interest is ligated into T-DNA so that it automatically gets transformed into plant cell thus, Agrobacterium tumefacien is known as “Natural Genetic Engineer” of plants.
6.Mention the important tools required for genetic engineering technology?
Ans.The process of genetic engineering is accomplished only when we have following key tools :-
a)Restriction enzymes:- Restriction enzymes are a group of endonucleases which cut the DNA at Specific position anywhere in its length. Each restriction endonuclease functions by inspecting the length of DNA & binds to DNA at the recognition Sequence.
b)Cloning Vector:- The DNA molecule which carry the desired DNA Segment of an organism & transfer it to cell or DNA of another organism is called cloning vector.
c)Desired foreign DNA:- The segment of DNA containing genes having desired characters & which are being transferred into genome of another cell with the help of vector is called foreign DNA.
7. In the given figure, one cycle of polymerase chain reaction (PCR) is shown-
(a) Name the steps A, B and C.
(b) Give the purpose of each of these steps.
(c) State the contribution of bacterium Thermus aquaticus in this process.
Ans. (a) Denaturation Heat denatures DNA to separate complementary strands.
(b) Annealing : Primers hybridises to the denatured DNA strands.
(c) Extension : Extension of primers resulting in synthesis of copies of target DNA sequence. Enzyme Tag polymerase is isolated from the bacterium Thermusaquaticus. This enzyme induces denaturation of double stranded DNA at high temperature.
8.Describe the various steps involved in Recombinant DNA technology with the help of a well labeled. Diagram?
Ans. i) Identification of DNA with desirable Genes:- Other molecules in the target cell can beremovedby appropriate treatment & purified DNA ultimately precipitates out after addition ofchilled ethanol.
ii) Cutting the DNA at specific location :- After having cut the source DNA as well as vector DNA with Specific restriction enzyme, the cut out “gene of interest” from the source DNA & the cut vector with space are mixed & ligase is added.
iii)Insertion of Recombinant DNA into host cell :- Recipient cells after making them competent to receive takes up DNA in its surrounding. Recombinant DNA is introduced into suitable host cell by vector – based or vector – less method.
iv)Selection & Screening :- If a recombinant DNA bearing gene for resistance to an antibiotic is trAns.ferred into E-coli the host – cell become trAns.formed into ampicillin – resistant cells. Due to this amp gene one is able to select a trAns.formed cell in the presence of ampicillin. This amp r gene is called selectable marker.
v)Obtaining the foreign Gene product :- After having cloned the gene of interest & having optimized the conditions to induce expression of the target protein, one has to consider producing it on large scale.
9.Expand PCR? Describe the different Steps involved in this technique?
Ans. PCR stands for polymerase chain reaction.It is a technique for amplification of gene of interest
or to obtain multiple copies of DNA of interest.
The PCR requires primers, taq polymerase, target sequence, DNA sample &deoxyribonucleotides.
PCR includes number of cycles for amplifying DNA of interest invitro. Each cycle has three steps :-
a)DENATURATION:- The first step is denaturation of SNA sample in a reaction mixture to 940 c. During this step, DNA strand gets separated.
b)RENATURATION / ANNEALING:- The temperature is allowed to cool down to 500c to allow two oligo-nucleotide primers to anneal to complementary sequence in DNA molecule.
c)EXTENSION:- The temperature is raised to 750c. At this temperature, taq – polymerase initiates DNA Synthesis at 3-OH end of primer.
10.What are Restriction enzyme? Why do bacteria have these restriction enzymes. Show diagrammatically a restriction enzyme its recognition & the product it produces?
Ans. Restriction enzymes are endonucleases which recognize a specific sequence within DNA and cut the DNA within that sequence at a specific point. In bacteria, these restriction enzymes operates modification restriction system which modifies & cuts the foreign DNA entering into the bacterial cell& thus, provides immunity to bacterial cell.
Name of Restriction enzyme- EcoRI Substrate DNA on which it acts
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