Concordance of the RNA termini of recombinants from crosses between avian retroviruses with different termini.

In previous work we have analyzed the RNA of recombinants issuing from crosses between avian retroviruses with distinguishable oligonucletoide maps and have the origins of the different segments of the recombinant RNA. Several recombinants appeared to contain the 5′-proximal part of one parent and the 3′-proximal part of the other parent, however, the terminal regions themselves were not analyzed. We have now examined the 5′- and 3′-terminal RNase T₁-resistant oligonucleotides of the parents and the progeny of two crosses and found that in all cases the 5′- and 3′-terminal regions were derived from only one of the parents. Inasmuch as the parental RNAs are subterminally redundant, as in the ase of Pr RSV-C and AMV RNA, the progeny RNA have the same property. It is remarkable that the crossovers appear to take place with a high frequency close to the termini of the viral RNA.