What is "conserved sequence"

n. a DNA or protein sequence with a high degree of sequence identity to other sequences in that species, or in others.

In biology, conserved sequences are similar or identical sequences that occur within nucleic acid sequences (such as RNA and DNA sequences), protein sequences, protein structures or polymeric carbohydrates across species ( orthologous sequences) or within different molecules produced by the same organism ( paralogous sequences). In the case of cross species conservation, this indicates that a particular sequence may have been maintained by evolution despite speciation. The further back up the phylogenetic tree a particular conserved sequence may occur the more highly conserved it is said to be. Since sequence information is normally transmitted from parents to progeny by genes, a conserved sequence implies that there is a conserved gene.

It is widely believed that mutation in a "highly conserved" region leads to a non-viable life form, or a form that is eliminated through natural selection. What determines conserved and non-conserved is the environment. If for example, a microorganism with antibiotic resistance genes is in the presence of antibiotic, the antibiotic resistance genes will be highly conserved. If not in the presence of antibiotics, the genes will become non-conserved.