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  • Why DNA cannot pass through the cell membrane ? How can the bacteria be made competent to take up a plasmid ? Explain a method for introduction of alien DNA into a plant host cell. Name a pathogen that is used as a disarmed vector.

Why DNA cannot pass through the cell membrane ? How can the bacteria be made competent to take up a plasmid ? Explain a method for introduction of alien DNA into a plant host cell. Name a pathogen that is
used as a disarmed vector.

 

 

 

 
 
 
 
 

Answers (1)

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. This is done by treating them with a specific concentration of a divalent cation, such as calcium, 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 briefly at 42o C (heat shock), and then putting them back on ice. This enables the bacteria to take up the recombinant DNA.

Method to incorporate alien DNA in plant host cell-
Cells are bombarded with high-velocity micro-particles of gold or tungsten coated with DNA in a method known as biolistics or gene gun.
Disarmed vectors are the vectors, which when infect the cell transfers the recombinant DNA into the host. Agrobacterium tumefaciens is one such disarmed vector.

Posted by

Priyanka Kumari

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