64 GENETIC STOCKS AND BREEDING METHODS 



variance as the amount of information /, or \jV p — I p . If I p is the amount of informa- 

 tion about p contributed by a whole body of data, then I p jn = i p may be designated as 

 the amount of information contributed by a single individual. 

 We have already seen that 



1 d 2 L sr ( d 2 log m\ 



Therefore 



L = ni r 



2 1 d 2 log m\ 



2 1 d 2 log m\ 

 \ m -djr\ 



and 



which can be shown to be equivalent algebraically to 



The quantity i p is a constant for any particular kind of mating and value of/? and 

 can be calculated in advance and used as a weight by which to multiply the total number 

 of progeny to obtain I p . 



The test of significance is therefore 



_ _D_ D D 



W D VT p Vni p 

 with probability obtainable from a normal table, or alternatively, 



2 & 



D and I p have the useful property of additivity such that they can be summed for 

 different types of matings to give a test of significance based on all appropriate matings 

 available. 



Table 17 (adapted from Carter and Falconer 172 ) gives scores and values of i p for 

 the detection of linkage for a number of different types of linkage matings. A numerical 

 example will illustrate their use for this purpose. 



Table 18 gives the data of Fisher and Snell 379 on the linkage of ruby (ru) and 

 jerker (je) in the mouse. The calculations of D and I p are set out in the table. The 

 X 2 test for significance of the deviation of p from one half is 



. (-140.889)' 

 1 2655.111 



