STUDIES ON HIGH AND LOW NON- 

 DISJUNCTION IN DROSOPHILA 

 M E L A N O G A S T E R 



HV GHRT n()NNIi:i{ 



/OOTOMICAL INSTI'lUTE, UNIVICMSII Y Ol' STOCKHOLM 



IN this paper crosses are described involving the following genes: 

 In the chromosome I: yellow (body-color y 0,o), scute (bristles Sc 

 0,0), broad (wing br 0,6), prune (eye-color p/, 0,8), white (eye-color w 1,0). 

 eosin (eye-color w'' 1,5), facet (ommatidia fa 3,i), echinus (ommatidia 

 Cc 5,r)), ruby (eye-color /•/. 7,5), cut (wing ct 20,o), tan (body-color t 27,5), 

 vermilion (eye-color v 33,n), miniature (wing m 86,5), garnet (eye-color 

 g 44,4), forked (bristles / 56,5), Bar (eye-shape B 57,o). A number of 

 lethals. The combination Sc e,. Ct v g f is called X-pl and the com- 

 bination Sc b,. Ce ri, / / is called 6-pl. In the chromosome II: black 

 (body-color bi). In the chromosome III: sepia (eye-color Se), spineless 

 (bristles s«), kidney (eye-shape 7x), ebony and sooty (body-colors e 

 and e*), pink (eye-color p), white-ocelli (ocelli Wo), rough (om- 

 matidia To). In the chromosome IV: bent (wing bt), eyeless (eye-shape ). 



I. INTRODUCTION. 



Since Bridges wrote his often cited paper (Bridges 1916) on non- 

 disjunction we have got not only an exact proof of the chromosome- 

 theory of heredity but also a very clear idea about the mechanism 

 which produces exceptions to the regular criss-cross inheritance of sex- 

 linked genes. Thus, if we have a Drosophila female, which is homo- 

 zygous with respect to a recessive sex-linked factor, and if among her 

 offspring there occur matroclinous daughters and patroclinous sons 

 this means that there has been either primary or secondary non-dis- 

 junction. In primary non-disjunction the two X-chromosomes both 

 remain in the egg or both go out to the polar body. When an egg 

 containing two Ä':s is fertilized by a I'-chromosome-bearing sperm we 

 get a matroclinous daughter and when a non-A'-containing egg is ferti- 

 lized by an A'-carrying sperm the result is a patroclinous son. The 

 matroclinous daughters have thus the constitution XXY and during 



HeredUas IV. 6 



