In genetics, an enhancer is a short region of DNA that can be bound with proteins (namely, the trans-acting factors, much like a set of transcription factors) to enhance transcription levels of genes (hence the name) in a gene-cluster. An enhancer does not need to be particularly close to the genes it acts on, and need not be located on the same chromosome (see Interchromosomal associations between alternatively expressed loci). An enhancer does not need to bind close to the transcription initiation site to affect its transcription, as some have been found to bind several hundred thousand base pairs upstream or downstream of the start site. Enhancers can also be found within introns. An enhancer's orientation may even be reversed without affecting its function. Furthermore, an enhancer may be excised and inserted elsewhere in the chromosome, and still affect gene transcription.That is the reason that intron polymorphisms are checked though they are not transcribed and translated. Genetics (from the Greek genno γεννώ= give birth) is the science of genes, heredity, and the variation of organisms. ... The general structure of a section of DNA Deoxyribonucleic acid (DNA) is a nucleic acid — usually in the form of a double helix — that contains the genetic instructions monitoring the biological development of all cellular forms of life, and many viruses. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... A Trans-acting factor is a molecule, generally a protein, whose task is to regulate another molecule, usually by binding to a cis-acting element. ... In the context of genetics, a transcription factor is a regulatory protein that initiates the transcription of certain genes upon binding with DNA. The binding of a transcription factor to a specific DNA sequence can result in either an increased rate of transcription of the gene, known as activated transcription... Transcription is the process through which a DNA sequence is enzymatically copied by an RNA polymerase to produce a complementary RNA. Or, in other words, the transfer of genetic information from DNA into RNA. In the case of protein-encoding DNA, transcription is the beginning of the process that ultimately... In genetics, two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds are called a base pair (often abbreviated bp). ... Diagram of the location of introns and exons within a gene. ...

Currently, there are two different theories on the information processing that occurs on enhancers:

• Enhanceosomes - rely on highly cooperative, coordinated action and can be disabled by single point mutations that move or remove the binding sites of individual proteins
• Flexible billboards - less integrative, multiple proteins independently regulate gene expression and their sum is read in by the basal transcriptional machinery

External Links

• Transcription and Enhancers (Animation)

References

• Arnosti, David N. and Kulkarni, Meghana M. (2005). Transcriptional enhancers: intelligent enhanceosomes or flexible billboards? Journal of Cellular Biochemistry 94 890–898.