162 Inheritance of Coat Colour in Mice 



In the case of the first mating I made between blue mice and blue 

 lilac the numbers yielded in the F^ generation are peculiar. 



Instead of a ratio of 9 : 3 : 4 as I expected, I got 27 blacks, 17 blues 

 and 18 blue lilacs. 



The Fi mice were black and therefore the blue lilacs were carrying 

 the determiner for concentration. 



The formula for the blue lilacs may be represented as eDB, where 

 e is the absence of dark eye, D the factor for concentration, B the factor 

 for blackness. 



The blue mouse can be represented as EdB, where E is the presence 

 of dark eye, d is the absence of concentration. 



The figures given above may possibly be an indication of spurious 

 allelomorphism between the factor for dark eye and the concentration 

 factor. 



The F^ mating would then be EdeD x EdeD. The results would 

 then be a ratio of 2 black to ] blue to 1 blue lilac, giving calculated 

 results of 31 black to 15'5 blue to 15*5 blue lilac. 



I was unable to repeat the combination owing to either the blues 

 used being heterozygous in chocolate or the blue lilacs heterozygous in 

 concentration. 



If this interpretation be correct, then all the blacks should be hetero- 

 zygous and all the blues homozygous. Unfortunately I only mated a 

 few of the offspring. 6 blues only were mated and 3 of these died 

 without young, the remaining 3 were homozygous ; 5 blacks were mated, 

 3 died without young, one had only 4 young and these were all black, 

 and the fifth was heterozygous. 



The results of mating chocolate-lilac mice with dark-eyed varieties 

 may give rise to various heterozygous forms. 



Thus the F^ generation of a mating between chocolate-lilac and 

 blue (giving black Fi) was 



19 black, 2 blue, 5 blue lilac, 6 chocolate-lilac. 



If the mating was EeDdBb x EeDdBB, the calculated numbers 

 would be 18 black, 6 blue, 4 blue lilac and 4 chocolate-lilac. 



From a mating of chocolate-lilac and black heterozygous in blue 

 giving black ^i, I got 



10 black, 4 blue, 6 blue lilac and 2 chocolate-lilac. 



If the mating were as above between EeDdBb x EeDdBB, there 

 should be 12"3 black, 4*3 blue, 27 blue lilac and 2*7 chocolate-lilac. 



