Chromosomes are divided into two parts (p and q arms) with a constriction point called a centromere in the middle
The centromere can be located in different positions and this forms the basis for the four different classes of chromosome:
- Metacentric – centromere is in middle, meaning p and q arms are of comparable length (e.g. chromosomes 1, 3, 16, 19, 20)
- Submetacentric – centromere off-centre, leading to shorter p arm relative to q arm (e.g. chromosomes 2, 4 - 12, 17, 18, X)
- Acrocentric – centromere severely off-set from centre, leading to much shorter p arm (e.g. chromosomes 13 - 15, 21, 22, Y)
- Telocentric – centromere found at end of chromosome, meaning no p arm exists (chromosome not found in humans)
Types of Chromosomes
