Plant Genetics

Macrotransposons

DNA transposons are efficient chromosome restructurers. Paired transposons, a common transposition outcome, cause chromosome breaks with frequencies inversely related to the distance between them. Huang and Dooner (2008) have shown that, in addition to breaks, transposon pairs in direct orientation produce many heritable rearrangements, including transposition of a macrotransposon extending from the 5' end of one transposon to the 3' end of the other. Chromosome breaks and rearrangements can be explained by alternative transposition reactions involving either the two internal or two external ends of the macrotransposon. The figure shows the mosaic color of maize kernels undergoing breakage-fusion-bridge cycles, which are initiated by alternative transposition of the macrotransposon's internal ends from one chromatid to its sister.