50 A. D. HERSHEY AND RAQUEL ROTMAN 



respect to the host-range character. In each case the yield was the same with- 

 in experimental error, seven percent of the total virus. This experiment shows 

 that the small yield of recombinants (one percent of wild type) in the cross 

 hXrlJ cannot be attributed to suppression of a hypothetical conjugation, 

 which would affect the interaction of h rl with rl3 as well, but indicates some 

 kind of linkage between the genetic factors concerned. 



AVERAGE YIELDS OF VIRUS IN CROSSES BETWEEN HOST-RANGE AND r MUTANTS 



Six crosses have been studied by the single burst technique; namely, hX.rl, 

 hy,r7, hXrJJ and the corresponding reverse crosses, h rX wild type. Each 

 cross was made three to five times for the collection of the single burst data, 

 and each time the viral yield was examined also from a culture tube containing 

 about 40,000 mixedly infected bacteria. The average yields from the culture 

 tubes are summarized in table 2. They show that the h locus is very closely 

 linked to rl3 (less than one percent of wild type), and that the linkage rela- 

 tions to rl and r7 are approximately what would have been predicted from this 

 fact, respectively 12 and 6 percent of wild type. According to arguments 

 previously given (Hershey and Rotman 1948), the factors /;, r7, and rl3 are 



Table 2 



A verage Percent Distribution of Viral Types in Yields 

 from about 40,000 Mixedly Infected Bacteria 



The results shown are from the same experiments for which single burst data are also re- 

 ported, except that one growth tube was lost among the crosses hr7 by wild type. The total multi- 

 plicity of infection is about five of each type per bacterium; the adsorption period is five minutes; 

 the total incubation period one hour. The distribution of viral types is computed from the re- 

 sults of mixed indicator platings. The column headed eop(h) gives the efficiency of plating of h 

 virus on single indicator as compared with mixed indicator, and illustrates the mixed indicator 

 effect mentioned in Methods. The column headed p(h) gives the percent of virus containing the h 

 allele, and shows the effect of selection during growth. 



NO. OF 

 EXPTS. 



/?+r^ 



//r^ 



h^r 



hr 



eop(h) p(h) 



157 



