If the number of chromosomes in a cell changes as in Down's syndrome, or the mutation affects the whole chromosome, this is known as a chromosome mutation. Normally, chromosome mutations occur during meiosis and whilst they may be silent, they often lead to problems in development. Chromosome mutations include deletions, duplications, inversions and translocations.
- Translocations - a part of one chromosome breaks off and attaches to another
- Inversion- a part of a chromosome breaks off and joins in the reverse direction
- Deletion - a part of the chromosome is lost
- Duplication - a part of the chromosome gets duplicated.
