12 



Eesearch in Animal Breeding. 



[Apr , 



It was proved years ago that Mendel's principles of heredity 

 apply equally to animals and plants, and the importance of the 

 subject led the Board of Agriculture some years ago to set aside 

 a small grant from the Development Fund for research in 

 animal breeding. The sum allotted, less than £200 per annum, 

 only allowed of work being undertaken with small animals 

 such as poultry and rabbits, but this in itself was no disadvan- 

 tage, for the object of the work was not to improve the breeds 

 of rabbits and poultry, but to acquire knowledge of the laws 

 which underlie inheritance in animals generally. In this series 

 of brief articles an attempt will be made to indicate the drift 

 of these experiments, and their possible bearing upon economic 

 problems. Before doing so, however, some account must be 

 given of the nature of Mendel's discovery itself; this is the 

 corner stone of our present knowledge, and unless it is clearly 

 understood, later developments must prove unintelligible. 



The essence of Mendel's discovery may best be made clear 

 by a simple example, from cattle. The breeder knows, perhaps 

 only too well, that red calves are apt to appear occasionally 

 even in the most highly pedigreed breeds of Aberdeen Angus 

 or Holstein. They are rarely welcomed, and in most cases the 

 breeder would go to a great deal of trouble to ensure that they 

 never appeared in his herd. He tries to get rid of the taint by 

 vealing the red calves, but still they come from time to time. 

 He may try to explain their appearance as a throw-back to some 

 remote ancestor, and though this may ease his conscience it 

 does not help to purify the herd. Mendelism enables the 

 breeder to understand why these red calves appear, and 

 provides the knowledge which can be used to prevent their 

 ever appearing again. 



Let us suppose a Mendelian analysis of this case to be made 



in the usual way. The first step is to cross the red with the 



black, and it will be found that the pure black bull crossed 



with red cows will produce black calves only (see Fig. 1) . For 



this reason, black is said to be dominant to red, which is recessive. 



The next step is to mate together these first crosses, or Fl* 



animals as they are termed. It will be found that their 



progeny, the F2 generation, consists of both blacks and reds, 



but not mixtures of the two colours, and if a sufficient number 



* For the saVe of clearness in experimental work the cross is taken as thn 

 point of clopnrtnre. The first cro^s nniinals belong to the first filial = Fl 

 .i^eneration. Wh "n Fl animals are mated to^rethr-r they produce the 2nd filial or 

 F2 generation, F2 animals mated together give a 3rd filial or F3 generation, 

 and so on. Sitnilarlv in the other 'h're'-tion the parents are labelled as the 

 PI generation, the grandparents as the P2 generation, and so on. 



