Biotechnology Principles and Processes Test - 11

Stanley Cohen and Herbert Boyer worked on bacterium Salmonella typhimuriumin 1972 by isolating the antibiotic resistance gene by cutting out a piece of DNA from a plasmid which was responsible for conferring antibiotic resistance.

The Ampicillin resistance gene is used as selectable marker as it prevents the growth of non-transformants cells and promotes the growth of transformants only

Restriction enzymes are also called 'molecular scissors' as they cleave DNA at or near specific recognition sequences known as restriction sites. These enzymes make one incision on each of the two strands of DNA and are also called restriction endonucleases.

Transfer of DNA into bacterial cell by phage or virus is called transformation. Phage kills the bacterium so called bacteriophage.

The smallest segment of DNA in the agrose gel will be towards anode or positively charged ends. The DNA fragments are negatively charged and moves towards negatively charged anode.

Polymerase chain reaction (PCR) was discovered by Kary Mullis. PCR technique is used to amplify the DNA segments to obtain large number of identical copies.

Plasmid vector Pbr322 is a multipurpose cloning vector. In pBr322, B and R stand for Boliver and Rodriguez who discovered this cloning vector.

The nucleosome is the fundamental subunit of chromatin. Nucleosome is clearly seen in fungus called Yeast.

EtBR or Ethidium Bromide is widely used nucleic acid stain and very strong mutagen and carcinogen. It causes mutation that cause variation or introduction of new traits.

The protection is offered by the action of the methylase. The methylase recognizes the same target site as the restriction enzyme and adds a methyl group to a specific nucleotide in the restriction site. Methylated sites are not substrates for the restriction enzyme.

The bacterial DNA is methylated immediately following replication so it will not be a suitable substrate for restriction endonuclease cleavage.

Thus, the viral DNA is restricted in the bacterial cell by the restriction enzyme, and the bacterial DNA is modified by the methylase and is provided protection.