Gene composition and number of silent and coding changes per gene in HYRs.

aGenes derived from respective wt viruses are given in italics.bBlack bold font are genes derived from the hy donor virus PR8.cIncludes the coding change Cys42Phe in the PB1-F2 of the X-163 series of HYRs.dRT-PCR/RFLP analysis showed X-53 PB1 derived from NJ/76 [36], however sequence data showed X-53 PB1 is a mixture of both PR8 and NJ/76 PB1 genes and also had more numbers of ambiguities, hence not included in the analysis.eNYMC X-157 PB1was a mixture of both PR8 and NY/04 PB1 genes.A/A- PB1 is a mixture of PR8 and NY/04; A (PR8 PB1) had only one silent change, A (NY/04 PB1) had 13 silent and 2 coding changes.