CBSE 12th Standard Biology Subject Biotechnology: Principles and Processes HOT Questions 2 Marks Questions 2021
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CBSE 12th Standard Biology Subject Biotechnology: Principles and Processes HOT Questions 2 Marks Questions 2021
12th Standard CBSE
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Reg.No. :
Biology
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Explain giving reaons why an alien piece of DNA needs to be integrated to a specific sequence of host DNA for its cloning.
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A and B are two different cloning vectors in two different bacterial colonies cultured in chromogenic substrate Bacterial colonies with cloning vector A were colourless, whereas those with B were blue coloured. Explain by giving reasons the cause of difference in colour that appeared.
(a) -
A plasmid DNA and a linear DNA (both of the same size) have one site for a restriction endonuclease. When cut and separated on agarose gel electrophoresis, plasmid shows one DNA band, while the linear DNA shows two fragments. Explain.
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An alien piece of DNA needs to be integrated to a specific sequence of host DNA for its cloning. Is it true? if yes, explain. If this is DNA is not picked up by host cells. Can you suggest a reason for it?
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What would happen if you grow a recombinant in a bioreactor but forget to add antibiotic to the medium in which the recombinant is growing?
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(a) A recombinant vector with a gene of interest inserted within the gene of a-galactosidase enzyme, is introduced into a bacterium. Explain the method that would help in selection of recombinant colonies from non-recombinant ones.
(b) Why is this method of selection referred to as "insertional inactivation" ?(a) -
In Gel electrophoresis, the DNA fragments are placed in wells on a sheet of gelatin and an electric current is applied to the sheet. Based on DNA biochemistry in which side are the wells located? In which direction and why do the fragments migrate?
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Agrobacterium tumifaciens is a pathogen of several dicot plants. But for biotechnologists it is a boon. Justify?
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In nature A. tumifaciens which is called a natural genetic engineer, infects only dicots. Unfortunately many important crop plants are monocots and thus could not be easily transfacted. Scientists have discovered certain processes to introduce naked DNA molecules into the plant tissue that are not susceptible to A. tumefactions ? Explain any two.
(a) -
After completion of the biosynthetic stage the products has to be subjected through a series
a) List these processes?
b) What are they collectively known as?
c) List any other measures to be taken care of?(a)
2 Marks
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CBSE 12th Standard Biology Subject Biotechnology: Principles and Processes HOT Questions 2 Marks Questions 2021 Answer Keys
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1. The specific DNA sequence where the replication of DNA is initiated is called origin of replication(Ori)
2. For the multiplication of the alien DNA in the host it has to be integrated to the origin of replication(Ori) -
On the basis of colour production in the presence of chromogenic substrate, the recombinants and non-recombinants can be differentiated. In this, a recombinant DNA is inserted within coding sequence of an enzyme \(\beta\)-galactosidase, which results in inactivation of enzyme.
In plate A. the bacterial colonies having inserted plasmid, shows no colouration. While in plate B. insertion of plasmid does not occur, therefore it shows blue colour. -
This is because plasmid is a circular DNA molecule. When cut with enzyme, it becomes linear, but does not get fragmented.
Whereas, a linear DNA molecule gets cut into two fragments. Hence, a single DNA band is observed for plasmid while, two DNA bands are observed for linear DNA in agarose gel. -
Yes, for the multiplication of alien DNA in the host, it has to be integrated to the origin of replication. The host cell is not compom=nent hence it is not picking up the foreign DNA.
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In the absence of antibiotic, there will be no pressure on recombinants to retain the plasmid (containing the gene of your interest). Since, maintaining a high copy number of plasmids is a metabolic burden to the microbial cells, it will thus, tend to lose the plasmid.
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(a) Bacteria are grown in a medium with chromogenic substrate, colonies formed show blue colour-no recombinants, no blue colourpresence of recombinants.
(b) Gene for the enzyme is inactivated by insertion. -
DNA is loaded on the cathode side of the gel. Since DNA is negatively charged the fragments move towards positive pole (anode) when the electric field is applied.
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It is considered as a natural genetic engineer. The Ti-plasmid of the bacterium is modified and used as a cloning vector to deliver the genes of our interest into a variety of plants.
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For explanation refer text book.
a. Micro-injection
b. Biolistics -
a. Separation, purification
b. Downstream processing
c. Quality control testing
2 Marks
