32 
BULLETIN 905, U. S. DEPARTMENT OF AGRICULTURE. 
It was thus very easy to fix the chestnut color in the Suffolk 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. 
