Cytogenetics of Oenothera 



111 



i 



//. 



A. COMPLEXES DIFFERING BY ONE RECIPROCAL TRANSLOCATION 

 1.2 3.4 5.6 7.8 9.10 11.12 13.14 ' 



\ / \ II II I I I \-\ \i< 



2.3 4.1 5.6 7.8 9.10 11.12 13.14 



I ^ 



B. COMPLEXES DIFFERING BY SIX RECIPROCAL TRANSLOCATIONS 



1.2 3.4. 5.6 7.8 9.10 11.12 13.14 



\ / \ / \ / \ / \ / \ / \ 

 2.3 4.5 6.7 8.9 10.11 12.13 14.1 



. I 



C. MURICATA RACE'S ACTUAL COMPOSITION OvQ\A 



1.2 3.4 6.5 13.12 7.11 10.9 8.14 



\ / \ / \ / \ / 1 / \ / \ 

 2.3 4.6 5.13 12.7 11.10 9.8 14.1 



A and B are theoretical 



FIGURE 20-11. Arrangement of chromosome ends in different Oenothera complexes. 



all such predictions came true. We see, then, 

 that the cytogenetic behavior of Oenothera 

 becomes understandable in view of its (1) long 

 previous history of reciprocal translocation, 



(2) method of chromosome segregation, 



(3) balanced lethals, and (4) self-fertilization. 

 At various points in this discussion Oeno- 

 thera seemed to behave exceptionally, ap- 

 parently violating our concepts of pure lines 

 and independent segregation. More com- 



plete analysis has shown, however, that the 

 failure of Oenothera to behave in the ways 

 expected was due to the operation of other, 

 already known, genetic events. Oenothera is 

 an exception which should be treasured, for 

 in the exact correspondence between its 

 atypical genetics and its atypical cytology, it 

 furnishes an outstanding example of the 

 validity of the chromosome theory of trans- 

 mission genetics. 



SUMMARY AND CONCLUSIONS 



Both the genetics and the cytology of Oenothera are exceptional. This, however, is found 

 to be the normal consequence of the simultaneous operation of certain already known cyto- 

 genetic phenomena. In this way, Oenothera provides an outstanding confirmation of the 

 validity of the chromosome theory of transmission genetics. 



