Heterogeneity of Pumpkin Ribosomal DNA

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Abstract
The ribosomal DNA (rDNA) of C. pepo L. consists of tandemly arrayed repeat units, most of which are 10 kilobases in length. Thirty-six repeat units, cloned into the HindIII site of pACYC 177, fall into 7 classes which differ from each other in length and/or nucleotide sequence. Most of the heterogeneity occurs in noncoding portions of the repeat unit although there is some nucleotide sequence variation in the coding portion as well. Heterogeneity of base modification was observed in genomic rDNA of which 2 examples are: all of the repeat units have 3 BamHI sties, one of which is unavailable for restriction in about half of the units and all of the CCGG sites except one are methylated at the internal cytidine in many of the units, a 2nd site is unmethylated in some of the units and in a very few units a 3rd site remains unmethylated.