FIG. 2.

Experimental strategy to detect gene conversion associated to cointegration. A shaded rectangle represents the nifH gene harboring different RFLPs (Fig. 1); the open rectangle corresponds to the wild-type nifH gene. Cointegration between circular molecules bearing these genes (indicated by crossed lines on the top part of the figure) generates three different types of cointegrate, depending on its possible association with gene conversion. In type a, a single crossover is depicted, without gene conversion. Gain of sites on both sides of the cointegrate (type b, sites A and N) or loss of sites (type c, sites A and N) is interpreted as evidence of gene conversion. The primers used to amplify each side of the cointegrate are indicated by numbered arrowheads.