NORMAL INHERITANCE 



43 



pink-eye dilution 18 times out of a hundred, then the three 

 genes must lie in the order: albino, shaker, and pink-eye 

 dilution. The indicated distance between albino and shaker 

 is about one-sixth that between albino and pink-eye dilution. 

 In Fig. 9 a number of determiners (genes) for mouse 

 unit-characters are represented as located upon diagram- 

 matic chromosomes of the mouse, to illustrate the genetic 



n 



VJ 



r\ 



u 



naked 



U 



r\ 



n 



agouti I 



white - 

 belly 



u u 



Olwailzer 



o 



Fig. 9. Diagram of chromosomes of the house mouse (22) with genes for unit 

 characters distributed arbitrarily among them to show genetic independence or 

 linkage of the characters. 



independence or linkage found experimentally to exist be- 

 tween these determiners. 



Besides the two linkage systems already mentioned {172), 

 linkage has been shown to exist between recessive spotting 

 and recessive hairless (161), and between short ears and 

 dilution (64-, 159). It is possible, as already suggested, that 

 agouti and white-belly may also be linked characters, rather 

 than allelomorphs. 



According to present data, known hereditary characters 

 have their determining genes located in 9 of the 20 pairs of 

 chromosomes of the house mouse. It is reasonable to sup- 

 pose that some day characters will be found in the remaining 

 11 pairs as well as other genes within those chromosomes 

 already bearing determiners for fancy variations. 



