292 



3 



CELL HEREDITY 



Complementation Map of the Pan-2 Locus 

 I II III IV V VI 



I I I I I I 



23, 28. 39, 65 



5 



69, 57, 70 



25,19,20,71,74,36 



% Prototrophs 008 

 in total viable — <-k — 

 spores 39 



CompI, 23/9 



r I 



Noncompl. 



Genetic Map of the Pan-2 Locus 



0,09 0-08 0.10 



75 7 19 



10 25 3 20 71 73 72 74 



_1 I I I I 1—1 L_ 



13 12 21 



006 



"~i — I rr— 1 — T" 

 49 32 2227 34 30 



CompI 23 65 5 69 57 70 61 ""9 



V " I i' ■ I 



Noncompl 2 6 I 



FIGURE 10.9. The pan-2 locus of Neurospora. Independently isolated alleles at the 

 pon-2 locus are denoted by number, and their location is shown both on the comple- 

 mentation map and on the genetic map of the region. Complementing alleles are 

 shown above the map line, noncomplementing alleles below the line (after Case and 

 Giles, 1960, Proc. Nafl. Acad. Sci. Wash., 46:659). 



another in the form of a complementation map, which is in principle 

 the same as a deletion map (Fig. 6.6). In complementation, however, the 

 damage is not a deletion, since these mutants revert to wild type. One 

 assumes that noncomplementation results from the presence of dam- 

 age in identical regions of the two mutants in question, and complemen- 

 tation from nonoverlap of damaged regions. Mapping then consists in 

 arranging all mutant pairs according to these criteria. Surprisingly, 

 when this procedure was followed with the pan-2 mutants (and with 

 those at other loci as well), a linear map was produced, and the order 

 correlated to some extent with that of the genetic map. The genetic 

 data have not been correlated with enzyme studies at the pan-2 locus, 

 but this has been done with the ad^ locus. 



Mutants at the adi locus lack the enzyme adenylosuccinase (see Table 

 10.1), and heterokaryons composed of complementing alleles show 2 to 

 25 per cent of wild-type activity. An extensive complementation map 



