NEET Practice Questions (MCQs) with Answers & Solutions

(c) Electroporation is the process used for ihc transformation of bacteria or plant protoplasts. Electroporation occurs as a result of the reconcentration of lipid molecules of the bilayer membrane to form hydrophilic pores in the membrane. The distribution of such pores, both in terms of size and number, determine the electrical properties of the cell membrane.

(b)  Reverse transcriptase is an enzyme used by retroviruses to from complementary DNA (cDNA) from their RNA. The resulting DNA is then inserted into the chromosome of the host cell.

(b) Processes of recombinant DNA technology involves isolation of DNA of desired DNA fragment. In order to cut the DNA with restriction enzymes, it needs to be in its pure form, free from other macro molecules. The DNA is enclosed within the membranes, we have to break the cell open to release DNA along with other macromolecules such as RNA, proteins, polysaccharides and also lipids. This can be achieved by treating the bacterial cells/plant or animal tissue with enzymes such as lysozyme (bacteria), cellulase (plant cells), chitinase (fungus). The RNA can be removed by treatement with ribonulease whereas proteins can be removed by treatment with protease.

(c) Eco R I is type II restriction endonuclease enzyme extracted from Eco R Y 13 bacteria. It can recognize and cleave 5'-GAATTC-3' palindromic sequence and is widely used in biotechnology experiments.

(d) pBR322 has a restriction site for Sal I.

(b) The vectors are DNA molecules that can carry a foreign DNA segment and replicate inside the host cell. Plasmid vectors are extra-chromosomal, self-replicating, usually circular, double-stranded DNA molecules, found naturally in many bacteria and also in some yeast. Although plasmids are usually not essential for normal cell growth and division, they often confer some traits to the host organisms, for example, resistance to certain antibiotics or toxins that can be a selective advantage under certain conditions. These naturally occurring plasmids have been modified to serve as vectors in the laboratory.

(b) Ti plasmid (tumour inducing) from the soil bacterium Agrobacterium tumefaciens is effectively used as vector for gene transfer to plant cclls. The part of Ti plasmid transferred into plant cell DNA, is called the T-DNA. Th;s T-DNA with desired DNA spliced into it, is inserted into the chromosome of the host plant where it produces copies of itself, by migrating from one chromosomal position to another at random.

In biolistic or gene gun method, 1-2 $\mu$g tungeston or gold particles coated with DNA to be used for transformation of plant cell. This device is able to transform almost any type of cell, including plants and is not limited to genetic material of the nucleis. It can also transform organells, including plastids.

E. coli plasmid pBR₃₂₂ is the most versatile and widely used cloning vector, it contains both ampicillin and tetracyclin-resistance genes and a number of unique restriction enzyme cleavage sites.