Tag: option b: biotechnology and bioinformatics

Biolistic guns are particularly effective for transforming plant cells, especially those that are difficult to infect with Agrobacterium or are recalcitrant to other transformation methods.

Agrobacterium tumefaciens is a natural genetic engineer; it contains a Ti plasmid that it naturally transfers into the host plant cell genome, causing crown gall disease. Scientists exploit this natural mechanism to introduce foreign genes.

Electroporation is a molecular biology technique where an electrical field of high field strength is applied briefly to cells to increase the permeability of the cell membrane, allowing the uptake of foreign genes or DNA.

Microprojectile bombardment (biolistics) is the most effective method for delivering DNA into complex tissues like immature embryos, as it can penetrate cell walls and reach deep into the tissue.

Polyethylene glycol (PEG) is a chemical agent used to facilitate the uptake of DNA into protoplasts (cells without walls) by inducing membrane fusion, which is a vector-free method of gene transfer.

Electroporation or electropermeabilization, is a molecular biology technique in which an electrical field is applied to cells in order to increase the permeability of the cell membrane, allowing chemicals, drugs, or DNA to be introduced into the cell. In molecular biology, the process of electroporation is often used to transform bacteria, yeast, or plant protoplasts by introducing new coding DNA.

Pollen culture (microspore culture) is a technique in which haploid plants are obtained from isolated pollen grains. Pollen or microspore culture is an in vitro technique by which the pollen grains, preferably at the uninucleate stage, are squeezed out aseptically from the intact anther and then cultured on nutrient medium where the microscope, without producing male gametes, develop into haploid embryoids or callus tissues that give rise to haploid plantlets by embryogenesis or organogenesis. Polyethylene glycol (PEG)-mediated cell fusion is a simple and efficient technique used widely for the production of somatic cell hybrids and for nuclear transfer in mammalian cloning. Fusion can be performed between adherent and suspension cells or between adherent cells or suspension cells. Cytokinins are the key factor to induce the direct shoot regeneration. Azolla form a symbiotic relationship with the cyanobacterium, Anabaena azollae, which fixes atmospheric nitrogen, giving the plant access to the essential nutrient. Pectinase is an enzyme that breaks down pectin, a polysaccharide found in plant cell walls. Cellulases contribute to the enzymatic splitting of cellulose, a component of cell wall.

• Several chemicals have been used to induce protoplast fusion.
• Sodium nitrate (NaN03), polyethene glycol (PEG), Calcium ions (Ca2+), Polyvinyl alcohol etc. are the most commonly used protoplast fusion inducing agents which are commonly known as chemical fusogens. 
• Hence, PEG is used for Fusing of protoplasts.
•  So, the correct answer is 'Fusing of protoplasts'.

Meiotic recombination is the result of crossover and independent assortment. Crossover is the exchange of genetic material between non-sister chromatids of a homologous pair that generate new genetic combinations; option D is correct. Telomeres are the structures present at the ends of linear eukaryotic chromosomes and have many tandem copies of a short oligonucleotide sequence with guanine residues in one strand and cytosine in the complementary strand. The G-rich strand has a few hundred nucleotides long overhang at the 3’ end which serves as the primer for its elongation by telomerase enzyme and thereby maintaining chromosome length; option A is incorrect. The independent assortment of non-homologous chromosomes during meiosis results in independent segregation of nonhomologous chromosomes; option B is incorrect. Centromere directs the formation of the kinetochore on its surface, a special protein structure that attaches to the microtubules in the mitotic spindle; option C is incorrect. The correct answer is D.

Gene transfer technologies include techniques of electroporation, microinjection, macroinjection, biolistics or microprojectiles for DNA transfer (particle gun), liposome mediated gene transfer, calcium phosphate mediated DNA transfer, use of DAE-dextran to transfer gene, polycation-DMSO for DNA transfer, polyethylene glycol mediated transfection and gene transfer through peptides.