noun, plural: submetacentric chromosomes
The centromere is the dense, constricted region in a chromosome. It contains highly-specialized repetitive DNA sequences (e.g. satellite DNA) that are packaged into heterochromatin. The centromere serves as the site for kinetochore assembly and therefore it is essential during the alignment of the chromosomes at the metaphase plate and the subsequent segregation of chromosomes during cellular division. The presence of the centromere results in the characterization of the chromosomal arms. The arm that is relatively shorter is called p whereas the one that is longer is called q. Based on the position of the centromere, the chromosome may be described as metacentric, submetacentric, acrocentric, telocentric, subtelocentric, and holocentric.
A submetacentric chromosome is a chromosome whose centromere is located near the middle. As a result, the chromosomal arms (i.e. p and q arms) are slightly unequal in length and may also form an L-shape. A chromosome with equal chromosomal arms is termed metacentric chromosome.
In humans, several chromosomes are submetacentric: chromosome 2, chromosome 4, chromosome 5, chromosome 6, chromosome 7, chromosome 8, chromosome 9, chromosome 10, chromosome 11, chromosome 12, chromosome 17, chromosome 18 and X chromosome.