Explain a chromosome deletion and the effect it can have on a human.

Chromosome deletion is a mutation (a genetic aberration) in which a part of a chromosome or a sequence of DNA is lost during DNA replication. Deletions can be caused by errors in chromosomal crossover during meiosis, which causes several serious genetic diseases. Small deletions are less likely to be fatal; large deletions are usually fatal — there are always variations based on which genes are lost. Some medium-sized deletions lead to recognizable human disorders, affecting muscle tissue, brain function etc.