Question

Briefly describe the different methods used to transfer the recombinant DNA into the host cell.

Hint:

Match the transfer method to the host: bacteria, animal cell, or plant cell.

Answer 1

Step 1: Understanding the Concept:
Once a recombinant DNA molecule has been built (gene plus vector), it still needs to physically get inside a living host cell before it can be copied or expressed. Different host types need different delivery methods.

Step 2: Describe transformation.
Bacterial cells can be made "competent" to take up foreign DNA by treating them with a specific concentration of calcium chloride, which increases the permeability of the cell wall/membrane, followed by a brief heat shock that helps the DNA enter.

Step 3: Describe micro-injection.
For animal cells, recombinant DNA can be injected directly into the nucleus of the cell using a very fine needle under a microscope, a method called micro-injection.

Step 4: Describe biolistics and vector-mediated transfer.
For plant cells, the biolistic or gene gun method fires micro-particles (like gold or tungsten) coated with DNA into the cells at high velocity, letting the DNA enter directly.
Alternatively, disarmed pathogen vectors, most commonly the bacterium Agrobacterium tumefaciens, are used to naturally carry and insert the desired DNA into plant cells.

Final Answer:
Recombinant DNA is delivered into host cells by transformation (bacteria, using CaCl2 and heat shock), micro-injection (animal cells), and the biolistic method or disarmed vectors like Agrobacterium (plant cells).