Genomics and Bioinformatics, Mapping of Genes, Spontaneous Mutations, DNA Technology, Genomics

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	Genomics and Bioinformatics- Beginning in 1910, geneticists have worked to identify and map genes in organisms of interest. The efforts were gradually centered on a few organisms, such as Drosophila, maize, mice, bacteria, and yeast. Mapping of genes involved the following two steps. The first step consisted of identification of spontaneous mutations or mutations induced by chemical or physical agents.
Once a set of mutations was available, they were used for linkage analysis and preparation of linkage maps. In some organisms, such as Drosophila, physical maps of gene's locations on chromosomes were also created. This approach was efficient and widely used in genetics. The drawback of this approach is that at least one mutation for each gene in the genome is required. But obtaining mutations is a difficult, labour intensive endeavour. In addition, the mutation must produce a phenotypic effect. But mutations often have lethal effect making it difficult or impossible to map the mutated gene.
Beginning in the mid-1980s, geneticists began to use recombinant DNA technology for genetic analysis. In this approach, a collection of clones, called a genomic library, is established. These clones are pieced together into overlapping sets and assembled into genetic and physical maps for the entire genome. In the final step, the clones are sequenced, and all the genes in the genome are identified from this sequence. Collectively, these methods are called genomics.