Evidence for somatic crossing over in chromosome six

In the previous article, we described an open-pollinated isolation plot in which nearly all the plants were heterozygous for Y1 y1. One ear out of a population of 37,957 consisted of two sectors (Fig. 1). About 3/4 of the ear had only yellow kernels, while the balance of the ear had a 1:1 ratio of yellow to white kernels (see kernel count, Figure 1). Such a sector could be produced if a somatic crossover had occurred in one of the primordial cells giving rise to the ear, followed by mitotic segregation of the crossover chromatids. If both y1 chromatids go to the same daughter cell, one cell lineage would be y1 y1 (giving rise to the 1: 1 sector upon open pollination), and the other cell lineage would be Y1 Y1 (giving rise to the yellow kernel sector).

Figure 1. Ear map showing twin sectors resulting from a putative somatic crossover.

Philip Stinard and Donald S. Robertson

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