284 Colour and Markings in Pedigree Hereford Cattle 



in the first generation proves the genetic constitution of the pgirents. 

 Both bull and cows must have carried the factor for too much white. 

 The five normally marked cows with which Lowland Paradigm was 

 mated, and which were proved by their produce to be heterozygous for 

 the character in question, had by him seventeen calves, twelve being well 

 marked and five badly. The ratio expected from the mating of hetero- 

 zygotes is 3 : 1 when dominance is, as in this case, complete ; but the 

 difficulty of getting at the facts when working with such small figures 

 is apparent, for the shifting of an individual from one class to another 

 will make all the difference whether the result agrees with expectation 

 or not. The figures obtained are 12 : 5, a really satisfactory agreement 

 with expectation. 



Lowland Paradigm was also the sire of thirteen calves from five 

 cows believed to be homozygous for the typical markings. These calves 

 were all normal in appearance. Half of them should according to theory 

 have carried the factor for excessive white, but unfortunately the majority 

 could not be tested as they were sold young, only three heifers being 

 kept to breed from. These three young cows proved when bred to a 

 bull known to carry the factor for white to be two pure dominants and 

 one heterozygote. The latter, Olive Oil by name, has so far produced 

 three well marked to one badly marked calf. This it will be noted is in 

 exact agreement with the expected 3 : 1 ratio. 



Lowland Paradigm's five badly marked calves from the cows that 

 carried the factor for white were, as would be expected, pure for excessive 

 white, i.e. they were extracted recessives. If we indicate those individuals 

 homozygous for the typical markings by the letters NN, those bearing 

 both factors by NW, then the calves referred to above will be of the 

 genetic constitution TTTT^ That this assumption was correct was 

 proved by their produce. Four out of the five were heifers and were 

 kept for stock. Up to date these young cows have had 21 calves by 

 heterozygous bulls, the result being 10 typically marked, to 11 with too 

 much white. 11 : 10 is again a very fair approximation to the expected 

 1 : 1 ratio that results from the mating of a homozygous recessive with 

 a heterozygote. 



To take now the produce of another bull, by name Bounds Chance 



^ As the white face of the Hereford is dominant in crosses with distinct breeds, and 

 even with species such as the bison, it seems that the white is due to the presence of a factor, 

 and not merely due to the absence of that for normal pigmentation, so I have indicated 

 excessive white by a capital IF, and not by the small letter which is used to show the 

 absence of a factor. 



