Analysis of ploidy (in megabase chromosomes) in Trypanosoma brucei after genetic exchange

The megabase chromosomes of Trypanosoma brucei are normally diploid, but th e extent to which this ploidy is maintained when parasites undergo genetic exchange is not known. To investigate this issue, a panel of 30 recombinant clones resulting from the co-transmission through tsetse flies of three di fferent parental T. brucei lines in all pair-wise combinations (STIB 247, S TIB 386 and TREU 927/4) were examined. These clones are products of 28 diff erent mating events; four of them result from self-fertilisation and the ot hers are Fl hybrids. DNA contents of the three parental lines were determin ed by flow cytometry and shown to differ only slightly with DNA content inc reasing in the order 927/4 < 247 < 386. Flow cytometry of the recombinant c lones indicated DNA contents were similar to the parents in 28 clones and r aised approximately 1.5 times the parental values in only two. The two Fl h ybrid progeny with raised DNA contents were shown by marker analysis to be trisomic for seven independent loci indicating that they were probably trip loid whereas progeny with DNA contents similar to parental values inherited a single allele from each parent for four independent loci indicating that they were diploid. (C) 1999 Elsevier Science B.V. All rights reserved.