Chromosomal Rearrangements in Nature 



239 



SUMMARY AND CONCLUSIONS 



Although the cytogenetics of Oenothera has several unusual aspects, present knowledge 

 renders these differences quite understandable; consequently, Oenothera provides an 

 outstanding confirmation o\ the validity of the chromosomal basis for genetic material. 

 Evolution in this genus is intimately associated with self-fertilization, balanced lethals, 

 and numerous reciprocal translocations. 



Pericentric inversions (which change chromosome shape) and whole arm reciprocal 

 translocations (which lead to changes in chromosome number) have been frequent in 

 the past evolutionary history of Drosophila. 



REFERENCES 



Cleland, R. E., "A Case History of Evolution," Proc. Indiana Acad. Sci. (1959), 69: 

 51-64, 1960. 



Cleland, R. E., "The Cytogenetics of Oenothera," Adv. in Genet., 11:147-237, 1962. 



Patterson, J. T., and Stone, W. S., Evolution in the Genus Drosophila, New York: Mac- 

 millan. 1952. 



White. M. J. D., "Cytogenetics of the Grasshopper Moraba scurra, VIII." Chromosoma, 

 14:140-145, 1963. 



Hugo De Vries (1848-1935), pio- 

 neer in the study of mutation and 

 Oenothera genetics. (From Genet- 

 ics, vol. 4, p. 1, 1919.) 



