Depending on the location of its centromere
(point of attachment of the spindle during mitosis),
a chromosome can be distinguished as
submetacentric, metacentric, acrocentric, or
telocentric. The centromere divides a submetacentric
chromosome into a short arm (p arm)
and a long arm (q). In metacentric chromosomes,
the short and long arms are about the
same length. Acrocentric chromosomes show a
dense appendage called a satellite (not to be
confused with satellite DNA) at the end of the
short arm. Satellite size differs for each acrocentric
chromosome of an individual (chromosomal
polymorphism). Telocentric chromosomes
have neither a short arm nor a satellite.
None of the human chromosomes are telocentric,
whereas all chromosomes are telocentric in
the house mouse, Mus musculus. However, it is
debatable whether telocentric chromosomes
actually exist as defined.
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