G

ene mapping in Xiphophorus is usually accomplished with the use of genetic "backcross" hybrids that are informative for a large number of polymorphisms between species. Today, isozyme, and RFLP technology has been mostly replaced with several variations of Polymerase Chain Reaction (PCR) technology. The use of Arbitrarily-Primed PCR (AP-PCR), and the development of microsatellite loci has proved to be a quick and reliable way of adding a large number of markers to the already existing linkage map. Once DNA has been prepared, a researcher can typically add between 5-10 polymorphisms to any genetic cross in a matter of about 1-2 work-days.

S

tatus of the Linkage map: At present, two distinct linkage maps have been created for Xiphophorus fishes. The first is derived from interspecific crosses between X. maculatus and X. helleri (H001BC1-B and H005BC1-B). Within these crosses, a linkage map has been created with coverage of all 24 chromosome sets. 403 mapped polymorphisms have been added comprised of 27 isozymes, 113 microsatellites, 192 AP-PCR/RAPD, 14 RFLPs, and 18 PCR-based gene polymorphism assays. The map coverage in this cross is 1 marker per 5.8 cM. The overall genome size is estimated at 2485.8 cM. One cM is estimated to comprise roughly 330 kB of DNA. This map can be explored below.

A second map has been created using hybrids between X. maculatus and X. andersi (H010BC1-A and B). This cross is predominantly comprised of microsatellite loci and has roughly 1 marker per 7cM.

We hope to use these maps in the immediate future to study the genetcis of melanoma and other neoplasms. Integration with BAC libraries to enable quick isolation of any locus that is hypothetically implicated in melanoma, and other neoplasms will be performed soon as well.

Summary of Xiphophorus Genetic Linkage Map
   (Referenced Walter et. al 2004)