Genomics

genomics, one of several omic branches of biological study, concentrates on the structure, function, and inheritance of an organism’s genome (its entire set of genetic material) . A major part of genomics is determining the sequence of molecules that make up the genomic deoxyribonucleic acid (DNA) content of an organism. The genomic DNA sequence is contained within an organism’s chromosomes, one or more sets of which are found in each cell of an organism. The chromosomes can be further described as containing the fundamental units of heredity, the genes. Genes are transcriptional units, those regions of chromosomes that under appropriate circumstances are capable of producing a ribonucleic acid (RNA) transcript that can be translated into molecules of protein.

meiosis

Every organism contains a basic set of chromosomes, unique in number and size for every species, that includes the complete set of genes plus any DNA between them. While the term genome was not brought into use until 1920, the existence of genomes has been known since the late 19th century, when chromosomes were first observed as stained bodies visible under the microscope. The initial discovery of chromosomes was then followed in the 20th century by the mapping of genes on chromosomes based on the frequency of exchange of parts of chromosomes by a process called chromosomal crossing over, an event that occurs as a part of the normal process of recombination and the production of sex cells (gametes) during meiosis. The genes that could be mapped by chromosomal crossing over were mainly those for which mutant phenotypes (visible manifestations of an organism’s genetic composition) had been observed, only a small proportion of the total genes in the genome. The discipline of genomics arose when the technology became available to deduce the complete nucleotide sequence of genomes, sequences generally in the range of billions of nucleotide pairs.