A marker (German “marker”, also called marker gene or molecular marker ) is used in molecular biology to describe e.g. B. uniquely identifiable, short DNA sections whose location in the genome is known, e.g. B. SNP ( Single Nucleotide Polymorphisms ).
Such marker genes are present in the genome (see types of markers below). However, marker genes can also be incorporated by genetic engineering. These reporter genes are chosen so that their presence in an organism can be easily recognized. For example, genes for fluorescent proteins or reporter enzymes are added to a microorganism along with other, less easily recognizable genes . Those of his offspring who have inherited the gene sequence can then be recognized, for example, by the fact that they fluoresce. With them there is therefore a very high probability that they have inherited those genes that are next to the marker gene in the added gene sequence. Genes that mediate resistance or eliminate auxotrophy are called selection markers. Marker genes that affect phenotype are called scorable markers . The first known markers were allozyme .
Uses of natural markers
- AFLP : Amplified Fragment Length Polymorphisms
- RAPD : Randomly Amplified Polymorphic DNA
- RFLP : Restriction Fragment Length Polymorphisms relate to cleavage sites for restriction enzymes .
- SNP : Single Nucleotide Polymorphisms - nucleotide variants. Certain SNPs are correlated with diseases and can therefore serve as molecular markers for a particular disease.
- STR analysis : Short Tandem Repeats are short repeating sections of up to 200 nucleotides that are repeated up to 20 times. The human genome has around 650,000 such microsatellites. Certain microsatellites occur with very specific diseases.
- VNTR : Variable number tandem repeats There are various places in the genome where VNTRs can be found. These loci are named for the genes they appear next to. In contrast to microsatellites (STR), they are longer repetitive sections.
- Conserved signature indel : some Indels are generic or species-specific.
- W. Wolz: Use of microsatellites as genetic markers , available as PDF from the University of Würzburg ( Memento from February 18, 2006 in the Internet Archive )
- C. Schlötterer: The evolution of molecular markers - just a matter of fashion? In: Nature Reviews Genetics . Volume 5, Number 1, January 2004, pp. 63-69, doi: 10.1038 / nrg1249 , PMID 14666112 .