Duck: Fur Sheep Crosses 



65 



PULTAVA, AN IMPORTED KARAKUL RAM 



He was supposed to be a pure blooded Karakul, but proved not to be as he sired many red, white, 

 and spotted lambs. About one-third of his offspring were off color, showing that he was hetero- 

 zygous for these desirable factors, and of little value for breeding purposes. Karakul sheep are 

 black but as they grow older their fleece turns gray, or nearly white, only the short hair on legs 

 and face retaining its original color. (Fig. 8.) 



or spotted, and 25 whites. The ques- 

 tion now arises, was this appearance of 

 such a large number of white, red, and 

 spotted lambs due to the known hete- 

 rozygous condition of the Fi ewes, or 

 was it the fault of the full-blooded, 

 imported sire, Pultava? Apparently 

 Pultava was the cause. On the basis 

 assumed in the original hypothesis one 

 of the 1912 and 1913 sires was hetero- 

 zygous for red (R), giving him the 

 form (BBRr). The Longwools (bbrr) 

 producing heterozygotes (BbRr) and 

 (Bbrr) in equal ratio. However, the 

 second sire produced no light colored 

 blacks out of over 100 lambs; it is 

 therefore safe to assume he was free 

 from the red color factor (R), making 

 his zygotic form (BBrr), with possible 

 gametes of (Br) only. The resulting 



zygote from a cross on the Longwools 

 would contain only a single dose of the 

 black factor (B), although, of course, 

 it is possible for a zygote, if properly 

 made, to have a double dose of any 

 factor. The only possible zygotic form 

 for the Fi ewes with respect to color 

 then is (Bbrr) and (BbRr), with a 

 mathematical ratio of three (Bbrr) 

 forms to one (BbRr) form, because one 

 sire produced only (Br) gametes, while 

 half of the other sires' gametes were 

 (Br) also. 



When the Fi ewes form gametes a 

 separation takes place between the part 

 of the zygotic cell containing (B) and 

 the part which does not contain it (b). 

 Half of the Fi gametes, therefore, will 

 be carriers of the black factor (B), 

 which Ls apparently correlated with the 



