Margaret C. Green, Ph.D. 



METHODS for TESTING LINKAGEt 



Methods for detecting and measuring linkage have been summarized and the 

 theory has been explained in an excellent monograph by Mather. 858 Tables of scores 

 which greatly simplify the calculations for the more common types of data have been 

 published by Carter and Falconer 172 for the detection of linkage and by Finney 364 and 

 Allard 7 for the estimation of recombination frequencies. Carter and Falconer 172 

 have also discussed the design of stocks for the detection of linkage and have suggested 

 a particular set of such stocks for the mouse. It is the intent of this paper to provide 

 only a brief introduction to methods of linkage useful for laboratory mammals, and to 

 direct the reader to the above and other sources for a more detailed discussion of the 

 methods and their rationale. The linkage testing stocks of the mouse maintained at 

 the Jackson Memorial Laboratory will be described and the latest linkage map of the 

 mouse presented. 



Linkage tests fall into two general classes, those in which the main interest is in 

 detecting linkage, and those in which the main interest is in measuring more exactly a 

 linkage already known to exist and determining the order of the two linked genes with 

 respect to other genes in the same linkage group. Positive tests of the first type, of 

 course, give preliminary information on the closeness of the linkage observed, but 

 usually more extensive tests using different stocks will be desirable. 



Whether the purpose of the mating is detection or estimation, only certain types of 

 matings will yield information of any kind about linkage. The necessary requirement 

 is that one of the mated animals should be heterozygous for each of the two loci with 



f Part of the work on which this paper is based was supported by research grants 

 NSF G-6200 and NSF G-7023 from the National Science Foundation and ACS E-162 

 from the American Cancer Society. 



56 



