A comparison of the DNA of the "R" and "T" strains of mosquito iridescent virus.

The buoyant density (1.7135 g/cm³), percentage GC (53.9%), and melting temperature (T_m = 76.4°) of the DNA of “regular” mosquito iridescent virus (RMIV) and of “turquoise” mosquito iridescent virus (TMIV) are similar although the molecular weights of the two DNAs are different; 243.3 × 10⁶ and 286.7 × 10⁶, respectively. Analyses show that RMIV contains two identical duplex DNA molecules which are about 15% smaller than the single duplex DNA molecule of TMIV. Reassociation studies show that RMIV and TMIV contain about 17 and 30% repetitious DNA, respectively. Homology studies show the two DNAs to be 100% homologous in their DNA nucleotide sequences. We conclude that the DNA of RMIV and TMIV contain identical sequences and that the portion of the TMIV-DNA molecule accounting for the higher molecular weight is composed of repeated sequences common to both strains.