Human mitotic metaphase chromosomes are identified by size, centromere location, and banding pattern

Human mitotic metaphase chromosomes are identified by size, centromere location, and banding pattern. The relative size, centromere locations, and banding patterns for three representative human chromosomes are shown. Chromosome 3 is one of the largest human chromosomes and, because the centromere is centrally located, is a metacentric chromosome. Chromosome 17 is a submetacentric chromosome because the centromere divides the chromosome into two arms of unequal size. Chromosome 21 has a centromere placed very close to one end and is called an acrocentric chromosome. In humans, the short arm of each chromosome is called the p arm, and the long arm is called the q arm. The symbol p was chosen for the short arm because it stands for the word “petit,” which in French means small. The symbol q was chosen for the long arm because it is the next letter in the alphabet.