Biotechnology Principles and Processes Test - 58

• The enzyme which can attack the free or the external end of the long polynucleotide chain is known as an exonuclease. 
• These are the type of nuclease enzymes which can attack on the free 3' or the 5' end of the nucleotide sequence. 
• These enzymes can cleave the phosphodiester bonds on either side of the nucleotide chain. 

Nanotechnology is the science and technology of building electronic circuits and devices from single atoms and molecules. Nanotechnology is used to describe many types of research where the characteristic dimensions are less than about 1,000 nanometers. Nanotechnology deals with the molecular make-up and organization of structures. By building materials from the nano-scale up, nanotechnology is able to project the unusual material functionality found at the nanoscale to a useful, applicable measure. Nanotechnology provides new and improved methods for making almost every manufactured products - better transportation, faster computers, energy developments and medical breakthroughs.

In 1979, Kary Mullis invented the polymerase chain reaction (PCR), a technique that amplifies specific DNA sequences from very small amounts of genetic material.

PCR and RFLP are the methods used for genetic fingerprinting. DNA fragmentation plays an important part in forensics, especially that of DNA profiling. Restriction fragment length polymorphism (RFLP) analyses the variable lengths of DNA fragments which are formed from the digestion of a DNA sample with a restriction endonuclease. They are then hybridized with DNA probes that bind to a complementary DNA sequence in the sample. In polymerase chain reaction (PCR), This sample DNA is amplified from a single copy to millions of copies of DNA. It used to amplify a specific region of a DNA strand. Most PCR methods amplify DNA fragments of between 0.1 and 10 kilo base pairs (kb), although some techniques allow amplification of fragments up to 40 kb in size. 

Metabolic engineering is generally referred to as the targeted and purposeful alteration of metabolic pathways found in an organism in order to better understand and utilize cellular pathways for chemical transformation, energy transduction and supramolecular assembly. Microbial catalysts are not as malleable as those in synthetic organic chemistry and metabolic engineers face many difficulties in the development of microbial catalysts: (i) cost and availability of starting materials (e.g., carbon substrates); (ii) metabolic route and corresponding genes encoding the enzymes in the pathway to produce the desired product; (iii) most appropriate microbial host; (iv) robust and responsive genetic control system for the desired pathways and chosen host; (v) methods for debugging and debottle necking the constructed pathway; and (vi) ways to maximize yields, titres, and productivities. The practical applications of biocatalytic chemical conversions are often restricted due to their complexities involving the unpredictability of product yield and the troublesome controls in fermentation processes.

Bacteria have restriction endonucleases, which cleave double stranded DNA at specific points. This prevents viral infection of by destroying the viral DNA introduced by a bacteriophage. Therefore, in order to prevent the destruction of its own DNA by the restriction enzymes, bacteria uses modification system where they modify their DNA by adding methyl groups. This modification must not interfere with the DNA base-pairing, and therefore, usually only a few specific bases are modified on each strand. 

Fermenter is an apparatus that maintains optimal conditions for the growth of microorganisms, used in large-scale fermentation and in the commercial production of antibiotics and hormones. 

A restriction enzyme (or restriction endonuclease) is an enzyme that cuts DNA at or near specific recognition nucleotide sequences known as restriction sites. To cut DNA, all restriction enzymes make two incisions, once through each sugar-phosphate backbone (i.e., each strand) of the DNA double helix. These enzymes are found in bacteria and archaea and provide a defence mechanism against invading viruses. Inside a prokaryote, the restriction enzymes selectively cut up foreign DNA in a process called as restriction.

Restriction enzymes are endonucleases that cleaves the DNA at specific sites. They are essential tools for recombinant DNA technology. The enzyme "scans" a DNA molecule, looking for a particular sequence, usually of four to six nucleotides. Once it finds this recognition sequence, it stops and cuts the strands. This is known as enzyme digestion. On double stranded DNA, the recognition sequence is on both strands, but runs in opposite directions. This allows the enzyme to cut both strands. Sometimes the cut is blunt, sometimes the cut is uneven with dangling nucleotides on one of the two strands. This uneven cut is known as sticky ends.