Biotechnology Principles and Processes Test - 10

Bioreactors are used to obtain biological products on large scale continually for commercial purpose. The sparged stirred tank bioreactor is advantageous over the simple stirred tank bioreactor as there is increased surface area for oxygen transfer. Tthe bubbles increase the oxygen transfer area.

X-gal is an analog of lactose, and therefore may be hydrolyzed by the β-galactosidase enzyme which cleaves the β-glycosidic bond in D-lactose.

X-gal, when cleaved by β-galactosidase, yields galactose and 5-bromo-4-chloro-3-hydroxyindole. The latter then spontaneously dimerizes and is oxidized into 5,5'-dibromo-4,4'-dichloro-indigo, an intensely blue product which is insoluble. X-gal itself is colorless, so the presence of blue-colored product may therefore be used as a test for the presence of active β-galactosidase.

This easy identification of an active enzyme allows the gene for β-galactosidase (the lacZ gene) to be used as a reporter gene in various applications.

Blades in a bioreactor help in mixing of all the components and prevent their settling at the bottom of reactor tank. It also increases the oxygen level in bioreactor.

Artificial Synthesis of DNA Without a Template: 

Hargobind Khorana and his colleagues produced the first synthetic DNA in 1965 by purely chemical means. They synthesised the gene coding for yeast alanine tRNA which needed only 77 base pairs. Unfortunately, this gene did not function.

Khorana and his associates, in 1979, synthesized the gene coding for tyrosine tRNA of E. coli. This gene had 207 nucleotide pairs. It functioned in combination with a phage DNA. When introduced into E. coli genes responsible for the formation of hormones somatotrophin and insulin have also been artificially synthesized.

A molecular-weight size marker, also referred to as a protein ladder, DNA ladder, or RNA ladder, is a set of standards that are used to identify the approximate size of a molecule run on a gel during electrophoresis, using the principle that molecular weight is inversely proportional to migration rate through a gel matrix. Therefore, when used in gel electrophoresis, markers effectively provide a logarithmic scale by which to estimate the size of the other fragments (providing the fragment sizes of the marker are known).

Agrobacterium tumifaciens is called natural genetic engineer. Modification in Ti plasmid of Agrobacterium tumifaciens is done to use it as a cloning vector by removing Ti genes.

If the gene of interest (goi) is inserted at the Bam HI site in the PBr322, the plasmid will lose tetracycline resistance which is necessary for successful hybridization of vector gene and foreign gene.

Restriction enzymes were discovered and characterized in the late 1960s and early 1970s by molecular biologists Werner Arber, Hamilton O. Smith, and Daniel Nathans.

For their work in the discovery and characterization of restriction enzymes, the 1978 Nobel Prize for Physiology or Medicine was awarded to them.

Modern genetic technology can be used to modify the genomes of living organisms. This process is also known as “genetic engineering.” Genes of one species can be modified, or genes can be transplanted from one species to another. Genetic engineering is made possible by recombinant DNA technology. Organisms that have altered genomes are known as transgenic. Most transgenic organisms are generated in the laboratory for research purposes.

The correct sequences of process of recombinant DNA technology are Isolation of DNA, fragmentation of DNA by restriction endonuclease, isolation of desired DNA fragment, ligation of DNA fragment into vector, transferring of into host and culturing in host cell to get desired product.