Chloroplast and Mitochondrial Genome Organization

Till now, we have dealt with genes present in the nuclei of eukaryotes. Certainly, nuclear DNA is the most important and very nearly the universal genetic material. But there are evidences for the presence of genes outside the nucleus.Till now, we have discovered that both the chloroplast and mitochondria have DNA of their own.

These DNA inherit independently of nuclear genes. In effect, the organelle genome comprises a length of DNA that has been localized in a defined part of the cell and is subject to its own form of expression and regulation. An organelle genome can code for some or all of the RNAs, but codes for only some proteins are needed to perpetuate the organelle. The other proteins are coded in the nucleus, expressed via the cytoplasmic protein synthetic apparatus. Genes not residing within the nucleus are generally described as extranuclear genes.