Spindle attachment defects. (a) In amphitelic attachment, the sister kinetochores are correctly connected to microtubules from opposite poles, resulting in a bioriented chromosome. (b) In a monotelic attachment, only one of the sister chromatids is connected to a spindle pole; the chromosome is mono-oriented. (c) In a syntelic attachment, both sister kinetochores are attached to a single spindle pole, and the chromosome is mono-oriented. (d) In a merotelic attachment, usually one or, rarely, both sister kinetochores are connected to both poles instead of one. Chromosomes are bioriented in merotelic attachments.