DNA sequence analysis of a 5.27-kb direct repeat occurring adjacent to the regions of S-episome homology in maize mitochondria.

The DNA sequence of the 5270-bp repeated DNA element from the mitochondrial genome of the fertile cytoplasm of maize has been determined. The repeat is a major site of recombination within the mitochondrial genome and sequences related to the R1(S1) and R2(S2) linear episomes reside immediately adjacent to the repeat. The terminal inverted repeats of the R1 and R2 homologous sequences form one of the two boundaries of the repeat. Frame-shift mutations have introduced 11 translation termination codons into the transcribed S2/R2 URFI gene. The repeated sequence, though recombinantly active, appears to serve no biological function.