Holocentric chromosomes

Abstract

In contrast to the normal type of monocentric mitotic chromosomes, where spindle attachment is restricted to a single kinetochore, holocentric chromosomes are chromosomes to which spindle microtubules attach along the whole length through kinetochores that cover a substantial part of their poleward surfaces during mitosis. In addition, holocentric sister chromatids are interconnected along their whole lengths before anaphase disjunction, unlike monocentric chromatids, which cohere only in the pericentromeric area. The morphological distinctions between monocentric and holocentric chromosomes are associated with differences in chromatin structure and modified mitosis or meiosis, as well as karyotype evolution of the holocentrics themselves. In this chapter, we will survey these aspects of holocentrism and also discuss some hypotheses on the origin of holocentric chromosomes, their patterns of occurrence and methods of verification, particularly among plants.