Tanksley,  S.  D.  Linkage  of  the  genes  coding  for alcohol dehydrogenase and phospho- glucomutase. Starch   gel   electrophoresis   of   extracts   from germinating  seeds  has  allowed  determination  of linkage  for  the  genes  coding  for  the  enzymes alcohol dehydrogenase and phosphor- glucomutase. For each enzyme, activity has been determined for only a single locus. F1 hybrids between  Solanum  pennellii  LA  716  and  Lycopersicon  esculentum  cv.  VF  36  were  backcrossed  to  the esculentum parent and the genotypes of the resulting seeds were determined.   Based  on  these  data  the  two  genes  appear  to  be  6/115  or  5  map  units  apart.  Segregation data from crosses as wide as L. esculentum x S. pennellii have been shown to give linkage values less than  those  from  strict  L.  esculentum  x  L.  esculentum  crosses.  Therefore  the  distance  between  the genes might not be so small as 5 map units. The undeniable conclusion is that the two  genes are linked and probably lie within a short distance of each other. This is especially interesting since the enzymes for which they code are both present in germinating seeds in high concentrations and both presumably  function  sequentially  in  the  same  metabolic  pathway  converting   starch   (storage carbohydrate)  to  ethanol  with  the  concomitant  release  of  ATP.  At  this  point  the  evolutionary  or regulatory significance of this linkage is only conjectural. In our initial description of the non-ripening (nor) mutant   (Tigchelaar   et   al.,   TGC   23,   1973), preliminary   evidence   from   F2   data  suggested repulsion phase linkage with the Tigchelaar, E. C., and R. J. Barman Linkage of the non-ripening  (nor)  and  uniform  ripening  (u) genes. uniform  ripening  gene  u  on  chromosome  10.  Testcross  data  (u+/nor/u/nor+  x  u/nor/u/nor)  has confirmed that nor is approximately 3.5 map units from u (Table). This close repulsion phase linkage has provided a convenient method to identify nor heterozygotes in F2.  

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