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Biology · 2022 · 5 marks
Biotechnology : Principles and ProcessesProcesses of Recombinant DNA Technology5 marksUnderstandlong answer
CBSE 2022 · Region 3 · Set 1 · Q13
(a) Read the paragraph given below and answer the questions that follow: Enzyme Taq polymerase, is extracted from a eubacterial microorganism Thermus…
Read the paragraph given below and answer the questions that follow : Enzyme Taq polymerase, is extracted from a eubacterial microorganism Thermus aquaticus from Yellowstone National Park in Montana, USA and isolated by Chien et al. ($\displaystyle 1976$). Taq polymerase successfully replaced the DNA polymerase from E.coli that was being used in PCR earlier and this shift revolutionised the PCR technique.
(i)
Taq polymerase after its discovery replaced E.coli DNA polymerase in PCR technique. Explain giving reasons why was the need felt for the change ?
(ii)
What is a primer and its importance in PCR ?
(iii)
Write the importance of PCR as a diagnostic tool.
Read the following paragraph and answer the questions that follow : Biotechnology revolves around the "gene of interest", with an objective to open various avenues for human welfare in health, medicine, pharma, agriculture etc. using different techniques, tools and processes. One of the breakthroughs of biotechnology in medicine is the gene therapy.
(i)
Name the human disease for which the gene therapy was used for the first time.
(ii)
Explain the steps of gene therapy carried to cure the disease using the lymphocytes of the patient. Why is this therapy not a permanent cure of the disease ?
(iii)
Write the possible permanent cure of the disease by the gene therapy that is in progress.
Marking-scheme solution
(a) (i) ● The E.coli DNA polymerase cannot carry out PCR at high temperature (as it becomes inactive).
Whereas Taq polymerase being thermostable remains active even at high temperatures.
(ii) ● Primers are small chemically synthesised oligonucleotides that are complementary to the regions of genomic DNA strand
-Primers help in extension of complementary DNA strand
(iii) Early detection of diseases like cancer / AIDS/ genetic disorder, by amplification of desired genes (when very low concentration of bacteria or virus before setting of the disease symptoms).
(b)
Adenosine deaminase (ADA) deficiency.
(ii) -Lymphocytes from the patient's blood are grown in a culture medium outside the body Using retroviral vector, a functional ADA cDNA, is introduced into these lymphocytes. Modified lymphocytes injected back to the patient body.
-Lymphocytes are mortal / not immortal, the patient requires repeated/periodic infusion.
(iii) Gene is obtained from bone marrow cells producing ADA is introduced into cells at early embryonic stage.
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CBSE Class 12 Biology past-paper question from the 2022 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.