When does neocentromere function and when does centromere function?
Answer Neocentromeres are rare human chromosomal aberrations where a new centromere has formed in a previously non-centromeric location. The emergence of a new centromere on a chromosome that already contains an endogenous centromere is normally a highly deleterious event which leads to dicentricity and mitotic instability of the affected chromosome. However, neocentromere formation also provides an important mechanism for the acquisition of a new centromere on chromosomal arm fragments that have separated during evolution from an endogenous centromere. Thus, neocentromeres can actually lead to mitotic stability of an acentric fragment. Neocentromeres have recently also been observed on apparently unrearranged chromosomes where the endogenous centromere has been inactivated. So, to answer your question: Yes, they can exist at the same time on the same chromosome but then the chromosome is highly unstable and may break apart. Or, one of the centromeres will become inactivated. Which one
