MATRIX ATTACHMENT REGIONS AND TRANSCRIBED SEQUENCES WITHIN A LONG CHROMOSOMAL CONTINUUM CONTAINING MAIZE ADH1

We provide evidence for the location of matrix attachment sites along a contiguous region of 280 kb on maize chromosome 1. We define nine po tential loops that vary in length from 6 kb to >75 kb. The distributio n of the different classes of DNA within this continuum with respect t o the predicted structural loops reveals an interesting correlation: t he long stretches of mixed classes of highly repetitive DNAs are often segregated into topologically sequestered units, whereas tow-copy-num ber DNAs (including the alcohol dehydrogenase1 [adh1] gene) are positi oned in separate loops. Contrary to expectations, several classes of h ighly repeated elements with representatives in this region were found to be transcribed, and some of these exhibited tissue-specific patter ns of expression.