Genomics

Abstract

Genomics is the study on how the complex sets of genes are expressed in cells (the term genomics was coined by Tom Roderick, a geneticist at the Jackson Laboratory, Bar Harbor, USA, in 1986). It’s a discipline in genetics that applies recombinant DNA, DNA sequencing methods and bioinformatics to sequence, assemble and analyse the structure and function of genomes. Though the term genetic engineering is modification of plants and animals through recombinant DNA technology, human beings have been actually practising genetic engineering for thousands of years. The rate of crop improvement was increased because of an in-depth understanding of genetics during the beginning of the twentieth century. Introduction of hybrid corn was the most dramatic agricultural development. But highly inbred lines gave decreased yield because of homozygous deleterious recessive alleles. As per the observation of George Harrison Shull, crossing of two different inbred lines gave progeny with “hybrid vigour”, with fourfold yield. Hybrid rice of the International Rice Research Institute in the Philippines gave 20% extra yield. Currently, breeders are looking for genes to optimize nutritional quality like golden rice. Rice is staple food for almost half the world’s population, but it lacks vitamin A. Vitamin A deficiency causes reduced vision and immunity. Genetically engineered golden rice is with vitamin A. It has been named golden rice because of the gold-coloured beta-carotene, a precursor to vitamin A. The intensity of golden colour increases with the presence of pro-vitamin A. The commencement of the twenty-first century made new ways to understand genomes. The complexity of plant genomes is multi-fold compared to eukaryotic genomes with evolutionary flips and turns of DNA sequences. Chromosome numbers ploidy levels are also widely different. The size of plant genomes (both number of chromosomes and total nucleotide base pairs) shows the greatest variation in the biological world. As an example, wheat contains over 110 times more DNA compared to Arabidopsis thaliana. Plant DNA contains sequence repeats, sequence inversions or transposable element insertions that modify the genetic content further.