Allometric genetics and reciprocal translocation backcrosses for general mapping

In the preceding report we completed the protocol for a thorough analysis involving p, recombination values and a and b, the allometric coefficients of the effects of genes A and B and the variance of all parameters. To evaluate the potential value of the procedure, analysis was illustrated in actual numbers with data from D.L. Langham (Genetics 25:88) involving F2 data between pd and tr and standard markers in crosses of maize with Durango teosinte. Searching for another batch of data with the widest possible interest we analyse here backcross data involving translocations T wx reported by E.G. Anderson, et al. (MNL 39:106-109, 1965). We picked only those which are in the waxy and nonwaxy reciprocal translocations listed in MNL 61:113, which are a standard set. The results are presented in Table 1. The p values were calculated by the Product Ratio method, by maximum likelihood and by our allometric method. Our method gives p values between the others, nearer to the maximum likelihood, and the p values are always smaller in the normal cases. But most important are the even smaller variances, so that a much more exact pooling of different sets of data can be arrived at by weighting the invariances.

There is no sign of allometrical effects indicated by the t values. In other words, semi-sterility affects equally all four classes a, b, c, d. The Product Ratio method exaggerates the strength of linkages, underestimating the error variances at the tight p values.

The mean of the 12 p values gives p = 5.91. In MNL 61:34-35 using our whole set of genetricks we obtained a mean p = 7.54 for 12 estimates of the standard T wx set, although between them only 2 are common. Of these, in 10 cases we believe that, more probably than not, the correct orientation was arrived at using information from some of our other reports. Perhaps a more realistic comparison is made by taking out 9L.10;5L.14, giving then p = 6.31 (it was deleted from the standard set). For the present set S.17;L.69 should then be taken out, and now gives p = 3.29 (it should also be discarded from the standard set). Taking into account also the common segregation for Krn factors, we can in many cases increase considerably the efficiency of the process of mapping as we have done in prior works. We think the correct mapping of T wx (and Krn factors) of utmost interest for greater marginal returns by getting the second approximation to the correct position in one strike.

Table 1. In this table are analyzed the data with those wx T9 translocations reported by Anderson et al. in MNL 39:106-109, 1965 that are listed in the standard translocations from the Cooperation Stock Center in MNL 61:113.

Luiz Eugenio Coelho de Miranda and Luiz Torres de Miranda

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.

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