Endonuclease recognition sites mapped on Zea mays chloroplast DNA

Abstract

The closed-circular DNA molecules of 85 .times. 106 daltons from Z. mays chloroplasts were isolated, digested with the restriction endonucleases Sal I [Streptomyces albus garcia], Bam I [Bacillus amyloliquefaciens] and EcoRI [Escherichia coli]. The resulting fragments was sized by agarose gel electrophoresis. A map of maize chloroplast DNA, showing the relative location of all the Sal I recognition sequences and many of the Bam I and EcoRI recognition sites, was determined. A DNA sequence representing approximately 15% of the Z. mays chloroplast genome is repeated. The 2 copies of this sequence are in an inverted orientation with respect to one another and are separated by a nonhomologous sequence representing approximately 10% of the genome length. The inverted repeats contain the genes for chloroplast ribosomal RNAs.