[ashwathi]

Whole set of genetic material or genes present in an organism are called as the genome of the organism. Study involving genome of an organism or different genomes of different organisms is termed as genomics. The determination of function of all the genes of a genome of an organism is known as functional genomics. This mainly involves study of location of gene expressions, the functions of the proteins produced and the interactions of corresponding proteins with any other biological molecules.

Expression profiling: The process of determination of the location of expression of each gene and the conditions required for the successful expression of the genes is known as expression profiling. Study of expression patterns of a whole genome of an organism is known as global expression profiling. This can be done by conducting study at either RNA level –involving direct sampling or micro arrays; or at protein level by mass spectrometry or protein arrays. Complete set of RNA molecules produced from the genome of the cell is known as transcriptome. A mature eukaryotic genome is so advanced that it has the capability to produce multiple mRNA from a single gene. The process by which the transcripts produced from genes undergo removal of introns and combining of exons to yield a functional mRNA is known as splicing. In alternative splicing, a single primary transcript RNA is spliced in different patterns. Each pattern of splicing results in different functional mRNA. The expression pattern in different tissues of same eukaryotic organisms differs. Thus, a set of genes expressed in one kind of tissue may not be expressed in some other. This wide study of different expression mechanism in the organism is done by expression profiling and the results are recorded.
Determination of gene function:
In functional genomics, it is important that the function of each and every gene be analysed. Several strategies have been applied for this; the most important one being mutational genomics. In mutational genomics, the function of a single gene can be noted by creating a mutation in the gene leading to loss or disruption of the gene function. The method involves isolating the particular gene, the function of which has to be determined, production of clone of the gene and inducing mutation leading to loss of function. This when re- introduced into the host organism, the loss of function of gene can be noted by analysing the different samples. Thus it has been made possible to analyse the function of each and every gene by inducing mutation to a single gene one at a time. The mutant strains during the experiments are collected to produce mutant genome libraries. One of the different methods adopted for the creation of such libraries are- creation of mutation in a single gene to produce single mutant which can be recorded to form a library. Another method involves induction of random mutations of several genes in a genome. Each mutation is then studied and the mutants are isolated forming the library. This is mostly conducted by insertional mutagenesis where mutation is caused by introduction of DNA into random sites of gene causing loss of function. The introduced DNA also serves as a tag aiding in isolation of specific gene. In yet another approach, the expression of a group of specific or random genes gets mutated in one impact.
Study of protein interactions:
Functional genomics also involves study of products of genes – that is proteins. Different interactions involving different proteins or that involving proteins and other molecules are studied. If behaviour of a protein is unknown, studying the proteins interacting with the corresponding protein reveals the properties of unknown proteins. The technique of protein interactions are studied by high throughput methods. Protein mapping made possible by use of library loaded with protein information, allows studying a large number of proteins at a time by screening methods. Screening of such interactions may be done by in vitro or invivo interactions. The data available from different screening methods are put together to form protein data bases. Different bio informatics tools have been developed to extract information from such data bases as and when necessary.
Thus, different techniques involved in functional genomics enable vast data accumulation, provides insights about the biological mechanisms like differentiation, response to diseases, etc. and has found applications in many fields like drug designing.