however , the 5 ' 37 codon of nicotiana chloroplast rps12 could not be identified by electron microscopy of rna-dna hybrids within a dna region extending 4000 bp upstream of codon 38 , nor by computer search of a completely sequenced region extending for more than 9000 bp upstream of this codon .
C0012854
dna
C0000702
a dna