Question

Review one new technology in molecular biology and its applications or its advance (more than 2000 words) .Please answer the question only if you can observe the minimum limit of 2000 words. Thank you

Answer 1

POLYMERASE CHAIN REACTION (PCR)

The advent of the polymerase chain reaction (PCR) radically transformed biological science from the time it was first discovered (Mullis,1990). For the first time, it allowed for specific detection and production of large amounts of DNA. PCR-based strategies have propelled huge scientific endeavors such as the Human Genome Project. The technique is currently widely used by clinicians and researchers to diagnose diseases, clone and sequence genes, and carry out sophisticated quantitative and genomic studies in a rapid and very sensitive manner. One of the most important medical applications of the classical PCR method is the detection of pathogens. In addition, the PCR assay is used in forensic medicine to identify criminals. Because of its widespread use, it is important to understand the basic principles of PCR and how its use can be modified to provide for sophisticated analysis of genes and the genome.

PCR has been used to facilitate cloning of known DNAs and to allow for the identification of novel DNAs. It can be performed directly on genomic DNA and on cDNA produced from mRNA (reverse transcription PCR (RT-PCR)). This eliminates the requirement for the production and screening of DNA libraries. When the target DNA sequence is known, the target DNA can easily be amplified using oligonucleotide primers based on the sequence. When only a portion of a target cDNA sequence is known, PCR can be used to amplify unknown sequences at the 5′ or 3′ ends of the known region (rapid amplification of cDNA ends (RACE)).2 Novel homologues of known proteins can also be identified using a method known as homology PCR.3 This method relies upon the use of degenerate mixtures of oligonucleotide primers designed to recognise conserved motifs. Homology PCR can be used to clone novel members of protein families or to clone protein homologues in other species.

PCR based techniques such as allele specific PCR and PCR restriction length polymorphism (PCR-RFLP) can be used to speed the detection of genetic polymorphisms in large populations. PCR fragments can also be sequenced directly, enabling screening of populations for novel mutations. PCR has been incorporated directly into DNA sequencing technologies, making possible the sequencing of small (nanogram) amounts of target DNA and sequencing of unpurified DNA—for example, for direct sequencing of DNA from bacterial colonies or phage plaques.4

ADVANCES IN PCR TECHNOLOGY

Since its introduction in the 1980s PCR has become a standard tool in biomedical research. The equipment (a thermal cycler) and reagents (thermostable polymerases, oligonucleotides, etc) required for PCR are widely available and relatively inexpensive. One advantage of PCR is its extreme sensitivity which makes possible the detection and analysis of low abundance DNAs. This is especially helpful when limited amounts of starting material are available, or when few copies of the target sequence are present. Applications of PCR include the cloning of known and novel genomic DNA and cDNA sequences, DNA sequencing, construction of mutant or chimeric DNAs, and quantification of mRNA and DNA. PCR is also used in certain methods of difference analysis