Abstract
We have found that the LA23 t/s mutant of Rous sarcoma virus (phenotype Prague B), even when passaged repeatedly at high multiplicity of infection, does not give rise to transformation defective deletion mutants comparable to those derived from RSV. In view of this fact and of the high rate of production of this mutant at 41 degrees C, we have undertaken a detailed analysis of the genome of this virus by ordering all large T1 oligonucleotides and by determining their nucleotide sequences. The results indicate a high degree of mutation in the onc gene as compared to that of Pr-A or Pr-B.