How do chromosome abnormalities happen?

Chromosome abnormalities may happen due to unexpected changes that occur during meiosis, mitosis, or due to exposure to mutagens such as chemicals or radiation resulting in changes in the chromosome structure or number, chromosomal rearrangement or missing chromosome. Several things can go wrong during meiosis. Some portions of chromosomes may lag, causing them to get left out during nuclei reorganization. Some chromosomes may be digested by nucleases. An error during chromosome division may cause a portion or the entire chromosome to get duplicated. These errors can result in structural or numerical chromosomal abnormalities. Exploring mutagens such as chemicals or radiation may result in a wide range of chromosome abnormalities depending on the type of mutagen, extent of exposure, and position of the mutation.