What is a part of a chromosome that determines specific traits?

A gene is a specific segment of DNA that provides the instructions for building proteins, which in turn determine specific traits in an organism. Genes are the basic units of heredity and carry the information necessary for the development of physical and biochemical characteristics. Each gene has a particular location (locus) on a chromosome and can exist in different forms known as alleles, which influence variations in traits.

The other terms listed refer to different aspects of cellular biology. A chromatid is an identical half of a duplicated chromosome, which plays a role during cell division, but does not itself determine traits. Spindle fibers are structures that help segregate chromosomes during cell division and are not connected to the determination of traits. Alleles are variations of a gene, but they are not the gene itself; rather, they contribute to the expression of a trait. Therefore, identifying a gene as the part of a chromosome that determines specific traits is accurate.