Cytological localization of highly repeated DNA sequences, the FokI sequence family and BamHI sequence families, in Vica faba chromosomes.

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Abstract
Cytological localization of one of the highly repeated DNA sequences of Vicia faba, the FokI repeat sequence family, was determined by in situ hybridization. This sequence family was described in our previous paper (Kato et al. 1984) as tandem arrays of 59bp unit sequences. The distribution pattern of silver grains showed that the FokI family sequences are exclusively localized in certain median regions in the long arms of all five pairs of the subtelocentric (S) chromosomes, but are not found in any portions in the metacentric (M) chromosomes. These median regions in the S long arms correspond closely to the positions of C-band heterochromatin revealed by preferential Giemsa staining. Since M chromosomes also possess C-bands, the absence of the FokI repeat sequences in the M chromosomes indicates that V. faba C-band heterochromatin consists of at least two different DNA sequences. V. faba chromosomes also contain other repetitive sequences, which have been characterized as the 250, 850, 900, 990, 1150, 1500 and 1750 by BamHI sequence families (Kato et al. 1985). In situ hybridization with nicktranslated 250 and 1500bp BamHI family sequences indicated that these repeated sequences are generally spread all over the chromosomes.