Final answer:
A piece of a chromosome that has lost its centromere is called an acentric fragment. This fragment cannot be properly included during cell division, leading to genetic mutations or cell dysfunction.
Step-by-step explanation:
A piece of a chromosome that has lost its centromere is referred to as an acentric fragment. This fragment lacking a centromere is no longer capable of proper movement during cell division. Chromosomes consist of chromatids, which are two identical copies of a chromosome joined together at a centromere before a cell divides. During the process of cell division, such as mitosis, cohesin proteins degrade and the sister chromatids separate at the centromere.
Each chromatid is then pulled towards the centrosome. If a piece of a chromosome loses the centromere, it will not attach to spindle microtubules and therefore will not be included in the daughter cells after cell division. Conditions like this often arise during chromosomal mutations termed deletions, where sections of a chromosome are lost, which can lead to significant genetic dysfunctions.