Conserved sequence< xmlnamespace prefix ="o" ns ="urn:schemas-microsoft-com:office:office" />
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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.
Conserved nucleic acid sequences
Highly conserved DNA sequences are thought to have functional value. The role for many of these highly conserved non-coding DNA sequences is not understood. One recent study that eliminated four highly-conserved non-coding DNA sequences in mice yielded viable mice with no significant phenotypic differences; the authors described their findings as "unexpected".[1].
The TATA promoter sequence is an example of a highly conserved DNA sequence, being found in most eukaryotes.
Conserved protein sequences and structures
Highly conserved proteins are often required for basic cellular function, stability or reproduction. Conservation of protein sequences is indicated by the presence of identical amino acid residues at analogous parts of proteins. Conservation of protein structures is indicated by the presence of functionally equivalent, though not necessarily identical, amino acid residues and structures between analogous parts of proteins.
Shown below is an amino acid sequence alignment between two human zinc finger proteins, with GenBank accession numbers AAB24882 and AAB24881. Alignment was carried out using the clustalw sequence alignment program. Conserved amino acid sequences are marked by strings of * on the third line of the sequence alignment. As can be seen from this alignment, these two proteins contain a number of conserved amino acid sequences (represented by identical letters aligned between the two sequences).
Conserved polymeric carbohydrate sequences
The monosaccharide sequence of the glycosaminoglycan heparin is conserved across a wide range of species.
Biological role of sequence conservation
Sequence similarities serve as evidence for structural and functional conservation, as well as of evolutionary relationships between the sequences. Consequently, comparative analysis is the primary means by which functional elements are identified.
Among the most highly conserved sequences are the active sites of enzymes and the binding sites of a protein receptors.
References
from： http://en.wikipedia.org/wiki/Conserved_sequence
保守序列
保守序列：指DNA分子中的一个核苷酸片段或者蛋白质中的氨基酸片段，它们在进化过程中基本保持不变。
在生物学中，保守序列指的是具有高度相似性或同一性的分子序列，这些序列可以是核酸序列（如RNA或DNA序列），蛋白质序列，蛋白质结构或糖类中的序列。这些序列高度相似，却来自不同的物种或同一生物体产生的不同分子。从跨种保留的角度来看，这种序列的存在意味着在形成不同物种的进化过程中，有一段特殊的基因序列被保留了下来。很多科学家认为，保留序列的基因区域发生突变会导致生命体无法存活或被自然选择所淘汰。
高度保守的DNA序列可能具有功能性价值。科学家们还没有理解这些高度保留的非编码DNA序列所扮演的角色。最近一项研究切除了小鼠身上4段非编码DNA片断，没有引起可繁殖小鼠明显的表型变异。研究人员称他们的发现“令人惊讶。
参考文献：
Ahituv N, Zhu Y, Visel A, et al. (2007). "Deletion of ultraconserved elements yields viable mice". PLoS Biol. 5 (9): e234
转自：http://www.dnaq.cn/360/titlec4e8a6c2b56111de9606bbb7f277b896.html
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