1390 



YEARBOOK, 1937 



Genetic Relationships Between Red, Cross, and Black Foxes 



Prior to 1928 no scientific research had been conducted to determine 

 the genetic basis of the red, black (silver), and cross coloring in foxes, 

 and consequently there was considerable confusion as to the genetic 

 relationship between the black color in standard and in Alaskan foxes. 

 In 1928 it was decided to include such studies in the program of 

 research for the United States Fur Animal Experiment Station. 

 B. L. Warwick, of the Texas Agricultural Experiment Station, coop- 

 erated with the late Karl B. Hanson, of the Fur Animal Station, and 

 proposed a hypothesis that would account for the results obtained. 

 To clarify the discussion somewhat, this hypothesis will be given first. 

 Warwick suggested that genes A and B and their alternative forms 

 (alleles) a and b account for red, black (silver), and cross colors in 

 foxes. All the possible combinations of these genes would give the 

 following types: 



AABB = Alaskan red. AABb — Smoky red. AAbb = Standard black 



AaBB=Cross. AaBb — Blended cross. (silver). 



aaRB=Alaskan black aaBb = Sub- Alaskan black Aabb — Substandard black, 

 (silver). (silver). aabb = Double black. 



Hanson found that when the standard black and the red foxes were 

 crossed, the offspring were usually a smoky red. Although red was 

 strongly dominant to black, it was not completely dominant; there 

 was some blending that produced the smoky color. Foxes of the 

 first filial generation had larger prominent dark points and more 

 evidence of black than is usually present in the red parents. Segre- 

 gation into reds, smoky reds, and blacks occurred when the first- 

 generation offspring were bred inter se, that is, bred to their own kind. 

 The ratio of segregation was about 1 red to 2 smoky red to 1 black. 

 When smoky red foxes of the first filial generation were backcrossed 

 to the black parents, the result was a ratio of 1 smoky red to 1 black. 

 These ratios indicated that a single gene accounts for the difference 

 between pure standard blacks and reds. 



On some fox farms, however, where supposedly pure standard black 

 foxes were bred with pure red ones, mixed litters of smoky reds and 

 reds in about equal proportions were produced in the first generation. 

 Doubtless the black (silver) parents were not pure but had a hybrid 

 combination of the genes A and a. 



Some red foxes caught m the wilds of Canada, the Upper Peninsula 

 of Michigan, and northern Minnesota and Wisconsin when crossed 

 with pure standard blacks produced mixed litters, with blacks and 

 smoky reds in equal proportions. If these wild red foxes were really 

 hybrids or smoky reds, it would account for the results. 



When Alaskan blacks were crossed with red foxes, the first genera- 

 tion were all cross foxes, but no appreciable dominance of black or 

 red was in evidence. Wlien the first filial generation was bred inter 

 se, there was a segregation of 1 red to 2 cross to 1 black (silver). The 

 cross foxes when backcrossed to black parents again produced crosses 

 and blacks in equal proportions. The ratios again indicated a differ- 

 ence of one gene between pure red and pure Alaskan silver foxes. 



Hanson then crossed Alaskan and standard black (silver) foxes. 

 The first filial generation turned out to be blended cross foxes. This 



