Strain-specific 1.7 kilobase repetitive deoxyribonucleic acid sequence family in Trichinella spiralis.

Eco RI digestion of bulk DNA from Trichinella spiralis P1, an isolate from domestic pig, reveals the presence of families of repetitive sequences. One of the most prominent of these has a monomer size of 1.7 kb, which exists in minimally dispersed direct tandem arrays, with a copy number of about 2800, and represents 2% of the genome. Although there is evidence that the Eco RI site is missing in some of the family members and that a 1.9 kb variant of the sequence also occurs, the family is highly homogeneous. When bulk DNA from other pig isolates (P2, PB1) and two black bear isolates from Pennsylvania (UPB6, UPB8) is probed with a typical member of the 1.7 kb sequence family cloned into pUC9, hybridization is identical in pattern and intensity with self-hybridization, indicating that the 1.7 kb family exists equally in the repetitive fraction of all of these isolates. When blots of bulk DNA from wild carnivore isolates (MSIL, PF1, AF1, AF2, AF3, AF4, SL, TC) are probed with pPRA, no hybridization can be detected. Faint hybridization of the probe to DNA from T. spiralis var. pseudospiralis occurs at 1.7 kb on an Eco RI profile and indicates that the 1.7 kb sequence has been conserved in the course of strain evolution.