Repeat sequence interspersion in coding DNA of peas does not reflect that in total pea DNA.

The pattern of sequence organization in the regions of the pea genome near sequences coding for mRNA differs significantly from that in total DNA. Interspersion of repeated and single copy sequences is so extensive that 85% of 1300 nucleotide-long fragments contain highly repetitive sequences (about 5000 copies per haploid genome). However, data presented here demonstrate that sequences which code for mRNA are enriched in the small fraction of fragments which do not contain these highly repetitive sequences. Thus, in contrast to the great majority of other sequences in the genome, most mRNA coding sequences are not located within 1300 nucleotides of highly repetitive elements. Moreover, our data indicate that those repeats (if any) which are closely associated with mRNA coding sequences belong to low copy number families characterized by an unusually low degree of sequence divergence.