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First generation sequencing also known as sanger method has revealed many new theories which include completion of human genome project & study of many other plant and animal genomes but due to its high costing and time taking results new method of NGS got developed in 20th-21st century which proved to be superior and typical Sanger method got replaced. NGS offers many advancements such as – it can produce large amount of data, it was able to read more than one billion short runs in single run and thus proved to be faster and cost effective method due to which accurate genomic information was produced. Preparation of sample which is needed in NGS is easy and fast to prepare and more correctly defined compared to Capillary based electrophoresis Sanger method. We can directly start with gDNA and cDNA library in NGS. In less than 1.5 hrs the DNA fragment gets ligated to platform specific oligonucleotides adapters; but in sanger sequencing needs genomic DNA that are fragmented and cloned into either bacterial chromosomes (BACs) and yeast chromosomes (YACs) and further BAC or YAC are sub cloned into a sequencing vector and get transformed to correct microbial host and before sequencing template DNA is purified from individual colonies which ultimately proves to be time consuming depending on size of genome.
Biologist have keen interest in researching the measurement of mRNA under different experimental conditions. In last decades microarray technology has been extensively used to monitor gene expression on a genome-wide scale simultaneously. In the technique of micro array cDNA is hybridized on an array of complementary oligonucleotide probes corresponding to gene sunder and abundant mRNA is completed fromits hybridization intensity. Allison et al 2006 & Ness 2007 gives detail discussion on micro array techniques & platforms , analysis of micro array data can be found in Quakenbush 2001 , Raza & Praveen 2012a , Raza & Praveen 2012b, Raza & Praveen 2013, Raza & Jaiswal 2013 , Raza 2014 , Raza & kohli2015 , Raza 2015 , Raza 2016. The study of cancer genomes and transcriptome is widely studied with help of micro array technology but its results are not up to mark due to microarray data limitations. Due to nature of probes included in platform microarray based expression profile only give a semi-quantitative assessment of genes and information of structural genomic aberrations and base pair mutation is not given by micro array technology. Therefore NGS has played major role in replacing microarrays which was not able to detect poorly expressed genes. In the year 2008 NATURE NEWS published an article ‘The death of micro arrays ‘, stating that ‘High Throughput Gene Sequencing seems to be stealing a march on microarrays’
DNA regions which interact with regulatory protein in functional regulation of gene expression are analysed for identification with help of NGS which is major tool. Therefore offering a keystones to characterisation & profiling of mRNA and small RNAs, DNA methylation patterns ( Ansorge 2009 ) and the most related application of NGS technique is analysis of transcriptomes is small non coding RNA (ncRNA)discovery & profiling. Small RNA or ribosomal RNA & transfer RNA are non-coding RNA molecules which are not translated in protein molecule. Recently the study occupies micro RNAs approximately 21-nucleotide long RNA molecules as post transcriptional regulators of gene expression. ( Morozova and Marra 2008 )

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