Polymorphisms in Trypanosoma cruzi: evidence of genetic recombination.

The ploidy of Trypanosoma cruzi is until now undetermined although analysis of isoenzymes, molecular karyotype and DNA content suggest diploidy in a very plastic genome. Also, there has been no convincing demonstration of genetic exchange and it has been proposed that reproduction is clonal. We have compared 18 T cruzi stocks and clones from the same area or host by means of isoenzyme analysis (12 loci) and restriction site polymorphisms in and around three glycolytic genes (glyceraldehyde-3-phosphate dehydrogenase, aldolase and glucosephosphate isomerase). The analysis demonstrated the presence of homozygotes and heterozygotes and is compatible with diploidy for these housekeeping genes. This strongly supports the hypothesis of genetic exchange in T cruzi and further elucidates the genetic diversity within natural T cruzi populations.