(1) Female homozygous for a sex factor 



The X Y type of inheritance. The gametic unions in 

 color-blindness in man may be represented as follows : 

 Let C = Factor for color blindness. 



c = Factor for absence of color blindness. 

 X and X = sex factors in female. 

 X and Y = sex factors in male. 



It is obvious that each person will have two kinds of 



gametes with regard to color-blindness. 



A normal male will have cX and Y gametes; 



a normal female will have cX and cX ; 



a color-blind male will have CX and Y; 



a color-blind female will have CX and CX and; 



a carrier- female will have CX and cX. 



The X chromosome carries the factor for color-blindness 



The variations from equality in the sex ratio may be 

 accounted for by one or more of the following causes: 1. 

 the spermatozoa are of two sizes, as shown by Wodsedalek 

 for the horse and the pig, the larger and less active with 

 the accessory chromosome being the female-producing; the 

 smaller and more active being the male-producing; 2. 

 the different chromatin content of the spermatozoa, may 

 have a bearing on their mortality. (See page 143). 



The gamete unions in color-blindness may be repre- 

 sented as follows: — 



Case 1. Color-blind male x normal female. 

 CX Y = male gametes ■ 



Female 

 Gametes 



CX 



cX 



i.e. In the children the normal males are as frequent as 

 carrier females. 



Case II. Normal male X carrier female. _ 

 cX Y = male gametes 



Female 

 Gametes 



CX 



cX 



i.e. Half of the males are color-blind, half normal, half of the 

 females are normal, half carriers. 



Ill 



