16 - Chromosome and Telomere Structure in Trypanosoma brucei

Abstract

This chapter provides an overview of chromosome content and structure in the parasitic protozoan Trypanosoma brucei. The genome of both the bloodstream form and insect form of the protozoan Trypanosoma brucei is diploid and consists of approximately 120 mitotically stable chromosomes. One hundred of these chromosomes are small, 50–150 kilobase (kb) minichromosomes, for which the genome may be considered aneuploid. Most of the roughly 20 larger chromosomes, accounting for 90% of the genome, can be grouped into homologous pairs. The identification of chromosome homolog is based on three criteria: (1) several housekeeping genes could be shown to distribute two differently sized chromosomes, generating specific linkage groups; (2) for most of these genes the physical maps of the flanking regions could be shown to be virtually identical over hundreds of kilobasepairs on the two different chromosomes; and (3) for one of the largest chromosome bands, which could not be further separated by pulsed field gradient (PFG) electrophoresis, in situ hybridization revealed two distinct sites of hybridization in the interphase nucleus, indicative of alleles of genes on homologous chromosomes.