Wednesday, November 27, 2013

DNA, Gene and Genome

DNA: Deoxyribonucleic acid, one of the two forms of nucleic acid in living cells. Polymers of nucleic acids. The genetic material of life. Each strand of DNA consists of a chain of four kinds of nucleotides (because of four different Nitrogenous bases). The order of nucleotide bases in a strand of DNA—the DNA sequence—is genetic information.

Gene: A DNA segment containing biological information which encode for an RNA and/or polypeptide molecule.

Genome: A genome is the full set of genes in each cell of an organism.

The hereditary nature of every living organism is defined by its genome, which consists of a long sequence of nucleic acid that provides the information needed to construct the organism. Genes are the basic unit of genetic information. They determine the nature and the function of the cell. The human genes (about ~ 30- 40,000) are referred to as the human genome. A genome is the full set of genes in each cell of an organism. It is the sequence of the individual subunits (bases) of the nucleic acid that determines hereditary features. By a complex series of interactions, this nucleotide sequence is used to produce all the proteins of the organism in the appropriate time and place. The proteins either form part of the structure of the organism, or have the capacity to build the structures or to perform the metabolic reactions necessary for life.

The human genome consists of two distinct parts:
1. Nuclear genome:
3.2 X 109 bp of DNA
30,000 – 40,000 genes
2. Mitochondrial genome:
circular DNA molecule of 16,569 nucleotides & consisting of 37 genes
Adult human body contains approximately 1013 cells.
Each cell has its own copy or copies of the genome.