Genetics of resistance to bacterial and parasitic infection / edited by D. Wakelin and J.M. Blackwell.

Date:
1988
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Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Genetics of resistance to bacterial and parasitic infection / edited by D. Wakelin and J.M. Blackwell. Source: Wellcome Collection.

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    Mode of inheritance of host response 55 Table 2.14. Calculations for goodness of fit to a single locus model using the Kolmogoroff-Smirnoff statistic as described by Fuller (1974). Explanation of the columns: A Class mid-point, i.e. 2-2 means 2-1 -2-3; B,C Observed number of Fl mice and NMRI mice, respectively ; D,E Frequency of Fl and NMRI in each class, respectively; F l/2(Col D)+ l/2(ColE). Were a 3:1 ratio being tested, then the two coefficients would be 1/4 and 3/4, depending on dominance; G Cumulative frequency for the parents combined ; H Observed animals in the backcross generation ; 1 Col H on a frequency basis ; J Cumulative frequency; К Difference between the two cumulative frequencies of Col J and Col G. The absolute value of the largest number in this column is X 100, which is compared with the tabulated values for the Kolmogoroff-Smirnoff statistic. In this case, for a sample size of 47, the critical tabulated value at alpha = 0-05 is 0-19. As theD^axof 0 1459 is less than the critical value, we conclude that we are unable to reject the hypothesis that the two distributions (i.e. the combined parental and the F2) are different, so the hypothesis of control by a single genetic locus would not be rejected. The distribution on the polygene hypothesis should be: 2/ (x) = N (XFl + XP, Vbx)/2 2 The log likelihood of this hypothesis is: log L (polygenes) log^ 2/ (x¿) I 2 [log L (one gene) - log L (polygenes)] is distributed as chi-squared with 1 degree of freedom. Example calculations are set out in table 2.16. They are tedious but not intrinsically difficult. They can be done quite quickly using the MINITAB interactive statistical package, and could be programmed in BASIC on any microcomputer. They could probably be done on a microcomputer using a spreadsheet program such as Lotus 1-2-3 provided the spread-sheet has the appropriate log and exponential functions. The main problem is to ensure that no arithmetic errors have been made. It might therefore be wise to try them out on the data presented in tables 2.15 and 2.16 to make sure that the calculations are
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