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Biotechnology: Principles and Processes — BIOLOGY STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceBIOLOGYBiotechnology: Principles and Processes4 Marks
Question
Explain the methods for making host cell competent to insert the r DNA.
✓

Answer

→ Since DNA is a hydrophilic molecule, it cannot pass through cell membranes.
→ In order to force bacteria to take up the plasmid, the bacterial cells must first be made 'competent' to take up DNA.
Micro-injection :
→ In a method known as micro-injection, recombinant DNA is directly injected into the nucleus of an animal cell.
Biolistics/ Particle bombardment :
→ In another method, suitable for plants, cells are bombarded with high velocity micro- particles of gold or tungsten coated with DNA in a method known as biolistics or gene gun.
Conformational change in the cell wall :
→ This is done by treating them with a specific concentration of a divalent cation, such as calcium, which increases the efficiency with which DNA 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 briefly at 42°C (heat shock), and then putting them back on ice.
→ This enables the bacteria to take up the recombinant DNA.

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