THE GENETIC SYSTEM AS A WHOLE 1 75 



List of Some Typical Characters Connected with the 

 Genes of Each of the Four Chromosomes of the 



Fruit-Fly 



In the lists, the part of the body, or the function, affected 

 by the character is first indicated. This is followed by the 

 names that have been applied to the different characteris- 

 tics. Many of these are self-explanatory; of some others a 

 brief characterization is given. 



Group I : X-chromosome. Sex-linked Inheritance. Eye- 

 color: Coral, blood, eosin, cherry, apricot, buff, tinged, 

 ivory, white (the foregoing are multiple alleles; that is, they 

 are all diverse modifications of the same gene). Modifica- 

 tions of other genes: vermilion, ruby, carmine, garnet. 



Eye Form or Structure: Bar, facet, furrowed. 



Body Colors or Markings: Yellow, sable, lemon, green, 

 chrome, tan, spot, dot, etc. 



Wings: Rudimentary, miniature, bifid, bow, notch, de- 

 pressed, club, fused, cut, etc. 



Legs: Reduplicated. 



Body Structure: Abnormal abdomen. 



Bristles: Forked, singed, tiny, bobbed, scute. 



Reactions to Light: Tan (individuals showing this color 

 characteristic do not fly toward the source of light, as do 

 the normal individuals). 



Life and Health: At least 10 different lethal genes are 

 known to be connected with the X-chromosome. Any one of 

 these prevents the animal from developing, if no correspond- 

 ing normal gene of the same pair Is present. All, or prac- 

 tically all, the characteristics in the above list cause the 

 organism showing them to be weaker and less resistant than 

 the normal "wild-type" flies. 



As will be seen from the above list, the genes of the 

 X-chromosome affect practically all parts of the body, and 

 many of its functions. 



