48 



INBEEEDING AND OUTBREEDING 



father. The sons, therefore, cannot be color-blind and 

 cannot transmit color-blindness, but the daughters, though 



(Normal) 



VaU tin* 

 (Color bUDd)| 



of parenVs 



o( paresU 



fiodjr-cellt 

 ot chlldreo 



Sex-cellt 

 ot cbildroa. 



Body-cells 

 of ^rand- 

 «bildrea 



FiQ. 16. — Diagram illustrating the inheritance of a sex-linked character such as 

 color-blindness in man on the assumption that the factor in question is located in the sex 

 chromosome. The normal sex chromosome is indicated by a black X, the one lacking 

 the factor for color perception, by a light X. It is assumed that a normal female is mated 

 with a color-blind male. (After Guyer. Courtesy Bobbs Merrill Co.) 



they will not be color-blind themselves because one normal 

 x-element is sufficient to determine normal vision, will 

 produce defective x-elements in one-half of their ova, 



