BERNARD O. PHINNEY 



University of California, Los Angeles 



Dwarfing Genes in Zea mays and Their 

 Relation to the GibberelUns'' 



Evidence has accumulated in the field of biochemical genetics to sup- 

 port the hypothesis that the gene acts as a physiological unit through 

 the control of a single chemical reaction (4, 6). Thus, a mutant gene 

 may determine a particular phenotype by interfering with a specific 

 step in a sequence of chemical reactions leading to a particular 

 product. This product may be any one of a number of substances 

 necessary for normal growth. The accumulated evidence also suggests 

 that nonallelic mutant genes concerned with the same growth sub- 

 stance control different steps in the reaction sequence leading to this 

 substance. 



In Zea mays L. there are more than twenty mutant genes^, each 

 of which results in the dwarf habit of growth (1,2,3). The non- 

 allelism is well established for all but one of the ten dwarfing genes 

 used in the studies reported here; nine of them are simple recessives, 

 one is a simple dominant. The knowledge of the precise genetical basis 

 for the dwarf habit of growth allows for the interesting speculation 

 that the normal allele of each dwarfing gene in some way controls 

 the presence, or at least the availability, of a substance necessary for 

 normal growth. Studies on the physiology and biochemistry of these 

 single gene mutants could lead to specific information on the bio- 

 chemical mechanisms controlling growth. It is the purpose of this 



^ Certain aspects of the studies reported here were supported in part by grants 

 from The University of California Reseach Committee, National Science Founda- 

 tion (G-3526), and Merck & Co., Inc. 



^The names and abbreviations for the nonallelic dwarf mutants of Zea mays 

 used in this paper are: dwarf 1 (d,); dwarf 2 (d.); dwarf 3 (d,); dwarf 5 (d^); an- 

 ther ear 1 (an,); nana 1 (na,); nana 2 (na,); petite 1 (tiny 4963) (pe,); and midget 

 2 (midget 8043) (mL). The linkage relationship of the mutant, dwarf 8 (domi- 

 nant dwarf) (ds) , is as yet unknown. 



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