(i) Describe the characteristics a cloning vector must possess. (ii) Why DNA cannot pass through the cell membrane ? Explain. How is a bacterial cell made competent to take up recombinant DNA from the medium?

(i) Describe the characteristics a cloning vector must possess. (ii) W

1.	(i) Describe the characteristics a cloning vector must possess. (ii) Why DNA cannot pass through the cell membrane ? Explain. How is a bacterial cell made competent to take up recombinant DNA from the medium?
Answer» A cloning vector must have the following characteristics : (a) ori or origin of replication (b) Selectable marker, which helps is identifying and eliminating non-transformants and selectively permitting the growth of the transformants. (c) Cloning site or recognition site for the restriction enzyme to recognise. (ii) DNA is a hydrophilic molecule, therefore it cannot pass through the cell membrane. The bacterial cells can be made competent by treating them with a specific concentration of a divalent ion like calcium. The cells are then incubated on ice followed by a heat shock by placing them briefly at `42^@` C and then putting back in ice.

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(i) Describe the characteristics a cloning vector must possess. (ii) Why DNA cannot pass through the cell membrane ? Explain. How is a bacterial cell made competent to take up recombinant DNA from the medium?

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