CONSERVED LOCATION OF GENES ON POLYMORPHIC CHROMOSOMES OF 4 SPECIES OF MALARIA PARASITES

The number of chromosomes and the chromosomal location and linkage of more than 50 probes, mainly of genes, have been established in four sp ecies of Plasmodium which infect African murine rodents. We expected t hat the location and linkage of genes would not be conserved between t hese species of malaria parasites since extensive inter- and intraspec ific size differences of the chromosomes existed and large scale inter nal rearrangements and chromosome translocations in parasites from lab oratory lines had been reported. Our study showed that all four specie s contained 14 chromosomes, ranging in size between 0.5 and 3.5 Mb, wh ich showed extensive size polymorphisms. The location and linkage of t he genes on the polymorphic chromosomes, however, was conserved and ne arly identical between these species. These results indicate that size polymorphisms of the chromosomes are more likely due to variation in non-coding (subtelomeric, repeat) sequences and show that a high plast icity of internal regions of chromosomes that may exist does not frequ ently affect chromosomal location and linkage of genes.