Genomic vs Plasmid DNA
Every organism has DNA, which controls the normal function of a cell, but some organisms have DNA in a cell, in addition to genomic DNA. They are plasmids. Both genomic and plasmid DNA are composite of nucleotides; therefore, the chemical structure of DNA is same in both. Although, both plasmids and bacterial genomic DNA are circular, eukaryotic DNA are linear, and all genomic DNA, either eukaryotic or prokaryotic, are double stranded.
Genomic DNA
Genomic DNA encodes proteins, which are responsible for structural and functional proteins. In eukaryotes, genomic DNA exists in the nucleus. Genomic DNA appears in prophase of cell division as chromosomes; otherwise, it appears as a bundle of strings called chromatin. These chromosomes are responsible for the transmission of the genetic information from generation to generation.
The unit of the inheritance i.e. genes, which is a small part of DNA, are arranged along the chromosome. When complexity of the organism is higher, more of DNA is there. In a human, there are three billion of base pairs and 23 pairs of chromosomes, whereas bacterium Escherichia coli has 4.3 million of base pairs.
Eukaryotic DNA is linear, and it is covered with a protein. Every organism has a constant number of chromosomes per cell, and that number is unique to an organism. In humans, chromosome number is 46.
In prokaryotes, genomic DNA is in the cytoplasm since they do not have a true nucleus. They are circular and have a small number of genes.
Plasmid DNA
Prokaryotic cells have plasmids, in addition to genomic DNA. These small DNA elements also have a small number of genes, but are not essential for the function of bacteria other than giving extra survival to the cell. Bacteria cell has several copies of plasmids.
Bacteria occur in extreme conditions too, so they need defense mechanisms. The genes, which reside in plasmids, are responsible for antibiotic resistance and metabolism of some substrates such as β-galactosidase (Wilson and walker, 2003).
Plasmids can be exchanged horizontally between bacteria, but this is not a step of cell division. Some plasmids can be exchanged between two different species. It helps to spread important trait for survival such as antibiotic resistant gene throughout the bacterial population.
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What is the difference between Genomic DNA and Plasmid DNA? • Plasmid DNA is smaller compared to genomic DNA. • Genomic DNA encodes proteins that are essential for function of the cell, whereas plasmid DNA is not essential for the function of bacteria other than giving extra survival to the cell. • Plasmid DNA is an extra chromosomal element, whereas Genomic DNA is not. • Plasmids can be seen frequently in prokaryotes, whereas some eukaryotes only have plasmids; i.e. E-coli. • Genomic DNA can be transferred to the daughter cell through the cell division only, and cannot be transferred horizontally, whereas plasmids can be exchanged horizontally between bacteria, but this is not a step of cell division. • Plasmid DNA has a higher rate of replication ability than Genomic DNA. • Plasmids are often used in recombinant DNA technology as a vector, whereas genomic DNA is not.
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Reference
Wilson. K., and Walker. J., Practical biochemistry: Principles and techniques, Cambridge University press, Cambridge
http://www.iechs.org/staff/Andrews/files
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