Restriction endonuclease analysis of the genomes of virulent and avirulent Marek's disease viruses.

The DNAs from virulent strain BC-1 and avirulent strains C2(A) of Marek's disease virus (MDV) were compared by electrophoresis on 0.5% agarose gels of the products obtained with the restriction endonucleases Bam H1, Sal 1, and Sma 1. The patterns of the fragments of the DNAs from these two strains were very similar, but showed some significant differences in the number and mobility of the DNA bands. The DNA fragments obtained with the restriction endonucleases, and especially Sma 1, were mostly present in equal molar ratios, but a few of those obtained with Bam H1 and Sal 1 were present in submolar amounts. In addition, several fragments obtained with Bam H1 and Sal 1 were present in greater than molar quantities, suggesting the presence of reiterated sequences in MDV DNA. The terminal fragments of MDV DNA were identified by their sensitivity to lambda 5'-exonuclease. The terminal fragments obtained with Bam H1 A and Sal 1B showed heterogeneous electrophoretic mobility and contained sequences with high content of guanosine and cytosine, suggesting the presence of reiterated sequences at the end of the MDV DNA molecule.