The Giemsa-staining centromeres of Nigella damascena.

The centromere regions of each chromosome in the complement of Nigella damascena (2n equals 2x equals 12) stain differentially with Giemsa at interphase and throughout all the principal stages of mitosis and meiosis. Each centromere is seen to consist of a pair of sister half-centromeres which appear as 2 differentially stained dots. The appearance and behaviour of these dots indicates that they are kinetochores. The technique used does not stain centromeres in other plant species investigated, a fact which shows that the centromeres of Nigella are in some way different. The implications of this observation in relation to centromere polymorphism are discussed.