The mapping of ghost genes: Chromosome two krn2(tr2) and the Michoacan 21 latente supergene

In the MNL we have been reporting a series of tricks to detect and analyse "invisible" genes. We will try to show by cross-checking the relative effectiveness of the procedures used, summing up the available evidence for Krn2 (tr2), lte1 and Lsc. The independent bits of information are as follows. J.S. Rogers (Genetics 35:541) reported linkage of lg1 with a tr factor. P.C. Mangelsdorf (Corn, its Origin and Improvement) reported linkage of lg1 with a tr factor. W.C. Galinat (D.B. Walden, ed., Maize Breeding and Genetics pp. 99-100) reported a tr factor between lg1 and the centromere. Miranda et al. (MNL 61:32), analyzing D.H. Langham's data reported a loose linkage between lg1 and tr but commented that the distance was grossly overestimated by direct measurement. Miranda et al. (MNL 60:35) placed Krn2 at 23, with B at 49. Miranda et al. (MNL 60:29) calculated the distances Krn 14.1 Lsc 32.9 fl, which gives on the map Krn2 at 21, Lsc at 35, and fl at 68. Miranda et al. (MNL 58:47) placed lte1 at 30, and B at 49.

By the pooled evidence there is a tr2 (Krn2) gene about position 22, most probably within the lg1 gl2 span. These are also the best prospective markers for the latente-1 locus, which is at about the 30-35 position in 2S.

These results also illustrate the use of Krn factors in general mapping. If it were not for the eerie precision of Krn2 mapping we would not have so much confidence in the latente gene's position.

Regarding the trpd phenomenon makes one remember one Iberic proverb which, translated to English, goes more or less as "I don't believe in sorceries but it exists, exists".

Luiz Torres de Miranda and Luiz Eugenio Coelho 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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