PCR amplification of microsatellite alleles. Results of PCR amplification of 3 microsatellite loci. RP = red parent J10; GP = green parent 1738; other lanes show alleles amplified from individual hybrid progeny clones from 3 flies. Both parental trypanosomes are heterozygotic at the II-PLC and III-2 loci, but only GP is heterozygotic at the XI-53 locus; for II-PLC the larger allele of RP appears as 2 closely spaced bands, but is inherited as a single band in progeny clones. The parental origin of each allele can be unequivocally identified by size for II-PLC, but for XI-53 RP is homozygous and for III-2, alleles a, b and d are closely similar in size and required long gel runs and application of samples in adjacent lanes to be distinguished. Each progeny clone has 2 strongly amplified bands and appears to have inherited one allele from each parent. Asterisked clones had 4N DNA contents; all other clones and parents were diploid, except for Fly 1 clone 18, which had 3N DNA content.