112 GENETICS IN RELATION TO AGRICULTURE 
trated by the cross yellow white female by gray red male. The genetic 
formula of a yellow white female is (ywX)(ywX), and of a gray red 
male (YWX)Y. In these formule y stands for the factor for yellow 
body-color and w for white eye-color, and the capital letters for the corre- 
sponding dominant allelomorphs present in the wild type. When two 
such flies are bred together the F’, consists of females of the genetic con- 
stitution (YWX)(ywX) and males of the genetic constitution (ywNX)Y. 
The F, females, therefore, have gray bodies and red eyes and the males 
have yellow bodies and white eyes. Gray red females of the genetic 
constitution (YWX)(ywX) produce four kinds of eggs in the following 
proportions: 
(YWX) 49.45 per cent. (ywX) 49.45 per cent. (Y¥wX) 0.55 per cent. (yWX) 0.55 per cent. 
98.9 per cent. non-cross-over gametes, 1.1 per cent. cross-over gametes. 
When such a female is bred to a yellow white male, genetic constitu- 
tion (ywX)Y, which produces only two kinds of sperms, (ywX) and Y, 
the progeny in both sexes obviously will be in the ratio 
49.45 gray red:49.45 yellow white:0.55 gray white:0.55 yellow red. 
Table X XI shows the results which have been secured, mostly from matings 
of this type. 
The relations shown when the factors enter in the reverse combinations 
may be determined by mating a gray white female, genetic constitution 
(YwX)(YwX) to a yellow red male, genetic constitution (yWX)Y. 
This gives /’; gray red females of the constitution (YwX)(yWX), and 
gray white males of the genetic constitution (YwX)Y. In this case 
the Fy females produce four kinds of eggs in the following proportions: 
(YwX) 49.45 per cent. : (yWX) 49.45 per cent. G (YWX) 0.55 per cent. :(ywX) 0.55 per cent. 
98.9 per cent. non-cross-ever gametes. 1.1 per cent. cross-over gametes. 
Taste XXI.—F actor Linkace In Gray Rep Femate Drosopuiwas OF THE TYPE 
(YWX) (ywX) 
| Non-cross-overs | Cross-overs 
Numb: | —— = 
Reported by of flies. i] alle | + ee 
classified Gray Yellow Gray Yellow ing-over 
red | white white | red F 
Dex tersupemuac tate ae | 14,939 | 8,093 | 6,672 | 93 Sleeves 
Morgan and Cattell.....) 1,818 | 1,075 729 14 Os | lec 
Morgan and Cattell... .. 854 | 513 334 | 2 | 5 | 0.82 
Morgan and Bridges.... | 3,424 1,807 1,600 | rh || 10 | 0.50 
| 
= = 
ERO balSMan anne iain | 21,035 | 11,488 | 9,335 116 | 96 | 1.01 
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