18 - Chromosomal Size Variations in Plasmodium falciparum

Abstract

This chapter discusses chromosomal size variations in plasmodium falciparum. The protozoan parasite Plasmodium falciparum causes the most severe form of human malaria, and it is, therefore, the subject of detailed study in an effort to devise an effective vaccine. The advent of pulsed field gradient (PFG) gel electrophoresis coupled with the increasing number of cloned probes has allowed the study of the structure of P. falciparum chromosomes and facilitates a more detailed account of the genetics of this organism. The genome of P. falciparum is organized into 14 chromosomes, a figure that has been arrived at independently through the resolution of the number of chromosome bands by PFG electrophoresis and also by counting kinetochores after reconstruction of a nucleus following electron microscopy of serial sections. The parasite is haploid in the asexual phase of the life cycle, and there is considerable variation in chromosome size from one parasite clone to another. A second component of chromosome size variation that has been identified involves amplification of the P. falciparum homolog of the multiple drug resistance (mdr) gene, a process that may have been driven by drug pressure in the field.