DATA FOR THE STUDY OF SEX-LINKED INHERIT- 

 ANCE IN DROSOPHILA 



T. H. MORGAN AND ELETH .CATTELL 



From the Zoologicnl Laboratory, Columbia University 



In recent years a new fact in Mendelian inheritance has come 

 to light, which while it obscures the Mendelian expectation based 

 on independent segregation of the factors of inheritance, shows 

 that the main Mendelian principles are by no means invalidated; 

 for, they too are manifest, but obscured by the linkage or coup- 

 ling of certain factors. When certain somatic characters are 

 associated with sex, as in Drosophila, we have the best oppor- 

 tunity, as yet afforded, for studying in its simplest form this 

 sort of 'associative' inheritance; for, in certain combinations, the 

 relation between linkage and breaking of the linkage ('crossing- 

 over' as we shall call it) is shown at once by the male flies which 

 indicate without complication the kinds of eggs that the Fi female 

 produces. In certain combinations both males and females give 

 this result. Such cases are those in which the sperm of the Fi 

 generation contains only sex-linked recessive or 'absent' char- 

 acters. 



In the following account we shall describe certain experiments 

 in which three linked characters (in addition to sex) are involved; 

 namely, red eyes, versus no red or white eyes; the black factor 

 for body color (giving black or gray flies), versus its absence 

 (which gives yellow or brown flies) ; and the factor for long wings 

 versus the absence of that factor (which gives miniature wings). 

 These characters show various strengths of linkage, i.e., the 

 number of times any two of them hold together differs for each 

 combination. This relation will be discussed after the data have 

 been given. 



Since these sex-linked factors follow the distribution of the sex- 

 chromosomes we may think of them as contained in these chromo- 



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