THE PROBABLE ERllOKS OF CALCULATKD LINK- 

 AGE VALUES. AND THE MOST ACOl'KATK 

 METHOD OF DETEUMININC; (JAMETIC FItoM 

 CERTAIN ZYOOTK^ SERIES. 



Bv J. B. S. HALDANK, M.A.. 



Fellow of New College, Oxford. 



In view of tho controversy lus to the cause of coupling and repulsion 

 it is desinible to know the probable err(»r of any j^iven deh'rniination 

 of a gametic ratio, and also t<i obtain from an observed zygotic serit^s 

 the most accurate possible estimate of the corresponding gametic series. 

 By the probable ern)r of an observation is meant of course a number 

 such that the difference between the true and observed values is ecpially 

 likely to exceed it, or to fall short of it. 



We shall consider the case of a heterozygote AaBb which pnxluces 



gametes in the proportions ^AB: — ~- Ab: ^ aB :^ <ib. In the 



£t It JL Z 



case of repulsion p is the cross-over value, in that of coupling 1 - p. If 



we write the gametic series in the case of coupling as 



xABAAh'.\aB:xab, 

 in the case of repulsion as 



\AB : yAh : yaB : lab, 



then X = -^ — , V = ^ . 



The values of />, x, and y may be obtained directly from the cross 

 AaBb X aahb. Here if n is the total number of zygotes obtained, P the 

 observed value of p, and (AB), (ab) the observed numbers of zygotes of 



compositions ABab and abab respectively, 7^= - . If n were 



ft 



infinite P and p would of course be equal, actually the probable error 



of Pis 



P{l-P) 



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V n 



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