Genetic analysis of Trypanosoma brucei
Analysis of trypanosomes derived from laboratory crosses showed that minisatellite inheritance is in agreement with a Mendelian system and that such markers are particularly useful for the detection of cross and self-fertilization. Examination of the F1 hybrids from these crosses has identified some hybrids as being trisomic, but that, contrary to previous reports, triploidy is rare. The rate of recombination between homologous chromosomes was also examined and used to estimate the physical distance per centiMorgan (4.9-25kb/cM).Although sexual recombination has been demonstrated to occur in laboratory experiments the extent of genetic exchange in natural populations remained to be elucidated. Analysis of a series of field samples isolated from tsetse flies indicated that a high proportion of tsetse flies harboured mixed T. brucei infections, a prerequisite for genetic exchange to occur in the field. Minisatellite variant repeat PCR (MVR-PCR) was employed, to map the interspersion patterns of variant repeat units within a minisatellite locus, a ternary code for a number of different alleles was generated and from this the underlying mechanism of mutation for one minisatellite (MS42) were inferred. This method of allele mapping was applied to a collection of field samples to study the relationship between T. b. brucei and T. b. rhodesiense populations and the extent of sexual recombination in natural populations in each sub-species. The analysis revealed that there is considerable sub-structuring in T. brucei populations, due to geographical barriers and host specificities. T. b. rhodesiense populations are distinct from T. b. brucei and a T. b. rhodesiense-specific marker has been identified for the Busoga (Uganda) focus.