What is the term for one of two identical chromosomes held together at a centromere?

The correct term for one of two identical chromosomes held together at a centromere is not spindle fibre, but rather sister chromatids. During cell division, specifically in the phases of mitosis and meiosis, chromosomes are duplicated and each duplicated chromosome is referred to as a sister chromatid. The centromere is the region where these two sister chromatids are joined together, allowing them to be pulled apart into two new cells during division.

Spindle fibres, found in the process of cell division, are the structures that help separate the chromosomes but do not refer to the chromosomes themselves. Homologous chromosomes are pairs of chromosomes containing the same genes but possibly different alleles, and they do not refer to identical chromosomes since they originate from different parents. A gamete is a reproductive cell (sperm or egg), and a zygote is the cell formed when two gametes fuse during fertilization; neither term applies to the sister chromatids concept related to the centromere.