Selection and identification of influenza virus recombinants of defined genetic composition

The RNAs of influenza virus recombinants were analyzed on polyacrylamide gels under conditions in which the derivation of specific RNA segments (including those coding for hemagglutinin and neuraminidase) could be determined. Analysis of the RNAs of recombinant viruses with identical hemagglutinin and neuraminidase revealed that the derivation of the remaining genes could be influenced by UV irradiation of one of the parent viruses. In five of seven such recombinants all of the remaining identifiable genes were derived from the nonirradiated parent, whereas in two others only the three largest RNA segments were derived from the nonirradiated parent. Analysis of the RNA pattern of a recombinant isolated after mixed infection in which neither parent was irradiated demonstrated a random mixture of RNA segments derived from the two parent viruses.