Why didn't Gregor Mendel find linkage?
IT is quite often said that Mendel was very fortunate not to run into the complication of linkage during his experiments. He used seven genes and the pea has only seven chromosomes. Some have said that had he taken just one more, he would have had problems. This, however, is a gross oversimplification. The actual situation, most probably, is shown in Table 1. This shows that Mendel worked with three genes in chromosome 4, two genes in chromosome 1, and one gene in each of chromosome 5 and 7. It seems at first glance that, out of the 21 dihybrid combinations Mendel theoretically could have studied, no less than four (that is, a–i, v–fa, v–le, fa–le) ought to have resulted in linkages. As found, however, in hundreds of crosses and shown by the genetic map of the pea1, a and i in chromosome 1 are so distantly located on the chromosome that no linkage is normally detected. The same is true for v or le on the one hand, and fa on the other, in chromosome 4. This leaves v–le, which ought to have shown linkage. ------------------ References 1. Blixt, S., in Handbook of Genetics, 2 (edit. by King, R. C.), (Plenum, New York, 1974).