

32 



BULLETIN 905, U. S. DEPARTMENT OF AGRICULTURE. 



It was thus very easy to fix the chestnut color in the Sussex Punch 

 breed, but on the other hand, all other colors are dominant or, as is 

 usually said, prepotent over it. The degree of prepotency depends 

 on the dominant factors which are homozygous. A homozygous 

 gray stallion (GG) will produce nothing but gray colts, however 

 crossed. A heterozygous gray (Gg) will produce 50 per cent gray 

 and 50 per cent not gray in crosses with mares which are not gray. 



Fig. 7. — The spotted coat pattern of this scrub stallion is due to a dominant hereditary unit and may be 

 expected to appear in half of his progeny. The curby hocks and other unsoundness are also strongly 

 transmissible. 



COLORS OF HOGS. 



Curiously enough we know less about the mode of inheritance of 

 colors in hogs than in the larger animals. The results of the first 

 crosses between the various breeds are, however, well known. The 

 white of Yorkshires and Chesters is more or less prepotent over the 

 red of Tamworths and Duroc- Jerseys, and, probably for a wholly 

 different reason, over the black of Hampshires, Berkshires, and 

 Poland Chinas. The black of Hampshires is prepotent over the 

 red of the red breeds. Berkshires and Poland Chinas, on the other 

 hand, when mated with the red breeds, produce pigs with a tortoise- 

 shell mixture of black, red, and often white spots. The white belt 

 of Hampshires, like the white patterns of many other animals, is 

 very irregular in its heredity. It is doubtful whether a given type 

 of belt can ever be completely fixed. 



