SEQUENCE OF CORRESPOXDIXG THIRD-CHROMO- 

 SOME GENES IN DROSOPIIILA MELANO- 

 G ASTER AND D. SIMULANS. 



A. H. STURTEVANT AND C. R. PLUXKETT. 

 CARNEGIE INSTITUTION OF WASHINGTON AND COLUMBIA UNIVERSITY. 



It has been shown (Sturtevant, 19210, b) that Drosophila 

 melanogaster and D. simulans may be crossed, and accordingly 

 it is possible to test suspected corresponding genes in the two 

 species. There is, for example, a recessive vermilion-like eye- 

 color (known as scarlet) in each species. If scarlet of either 

 species is crossed to the wild type (or to any other eye-color) 

 of the other species, the resulting hybrids have the wild-type or 

 "red" eye-color. Therefore each species carries the dominant 

 wild-type allelomorph of the scarlet mutant of the other species. 

 But if scarlet melanogaster is crossed to scarlet simnlans, the 

 resulting hybrids have scarlet eyes. Therefore the two scarlets 

 must represent modifications of the same wild-type gene, or at 

 least of wild-type genes that have like effects on development. 

 Such genes as the two scarlets are described in this laboratory 

 by the term "corresponding," rather than (as formerly) "allelo- 

 morphic" since it seems desirable to reserve the latter term for 

 genes that regularly separate at maturation. In the present 

 case the fact that all the hybrids are sterile prevents any test of 

 the segregation. 



A study of thirteen corresponding genes in the X-chromosomes 

 of melanogaster and simnlans (Sturtevant 19210, and unpublished 

 data) shows that the sequence of the loci concerned is the same 

 in the two species. But it was shown by Sturtevant (1921^) 

 that the sequence is not identical in the third chromosomes. 

 If the three corresponding genes scarlet (st), peach (p), delta 

 (A, formerly called "deltoid" in simnlans) are mapped, the 

 sequence is found to be stpA in melanogaster, stAp in simnlans. 



The present paper is a report on three additional pairs of 

 corresponding genes in this chromosome, which make it possible 



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