Linkage Mapping a Mutation in Arabidopsis

Abstract: Since Alfred Sturtevant constructed the first genetic map of a Drosophilachromosome in 1913, new mutations have been mapped using his method of linkage analysis. Determining the map position of a new mutation -- and its corresponding gene -- consists of testing for linkage with a number of previously mapped genes or DNA markers. Linkage is the principle that the closer two genes or markers are located to one another on a chromosome, the greater the chance that they will be inherited together as a unit (linked).  Conversely, locations farther apart on the chromosome are more likely to be separated by chromosome recombination during meiosis. Thus, the frequency of recombination with previously mapped genes or markers allows one to determine the map position of a gene of interest. The increasing availability of whole genome sequences and sophisticated computer software has made it possible to map genes using bioinformatic approaches.  However, traditional mapping techniques are still used to map genes for which no sequence information is available -- for example, mutant phenotypes produced by chemical mutagenesis.  Although early gene maps relied on genes and mutations with observable phenotypes, modern gene maps are populated with DNA polymorphisms that are detected by molecular methods. In Arabidopsis, molecular markers exploit the natural differences between distinct ecotypes, such as the widely used Landsberg (Ler) and Columbia (Col), which differ about 1% at the DNA level.

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