Question

Polyethylene glycol method is used for
(a) Energy production from sewage
(b) Gene transfer without a vector
(c) Biodiesel production
(d) Seedless fruit production

Answer 1

Polyethylene glycol (PEG) is useful for a molecular biological technique in the transfer of specific molecules in plant cells very efficiently. The technique also has high reproducibility.

Complete step by step answer:
- Plant cells have rigid cell walls, which inhibits the process of gene transfer. Hence, there are various techniques to transform the plant cells when they are in the protoplast stage. Before the protoplast regenerates the cell wall, the direct gene transfer is carried out.
- The PEG method is an efficient method of transforming plant cells by direct gene transfer.
- PEG transfer stimulates the uptake of liposomes (lipid vesicles used for the administration of smaller molecules in the cell) and improves the efficiency of electroporation. PEG transformation is preferred over electroporation in monocot protoplasts due to relatively high survival rates post-treatment.
- Plant protoplast is transformed with naked DNA in the presence of PEG and divalent cations like ${ Ca }^{ 2+ }$. They destabilize the plasma membrane and facilitate it for naked DNA permeation.
So, the correct answer is ‘(b) Gene transfer without a vector’.

Additional Information:
- Energy production from sewage can be carried out from a number of ways, especially those using microorganisms. Anaerobic microorganisms break down various compounds in sewage to give off byproducts such as methane gas which can be used as fuel.
- Biodiesel is produced from recycled vegetable oils and animal fats by transesterification reactions.
- Seedless fruits are produced by two techniques - parthenocarpy and stenospermocarpy.

Note:
- Other methods of gene transfer in plant cells are microinjections, biolistics (gene gun) , Agrobacterium -mediated gene transfer, silicon carbide whiskers, etc.
- The transformation efficiency of the PEG method is between 0.1 - 0.4 %.