Duplications also result from the reuniting of broken pieces of homologous chromosomes. In some cases the chromosome pieces rejoin in such a way that there is a doubling, or redundancy, of a portion of the chromosome. This changes the number of genes present and may result in a problem with health, development, or growth.

Large insertions and deletions prevent the production of useful proteins. The effect of smaller insertions or deletions depends upon how many bases homologous similar in structure


Schematic representation of four types of chromosomal aberrations.

are involved. Sometimes an entire gene can be inserted (in duplications) or deleted. The effect depends upon where in the genome the changes occur and how many base pairs are involved.

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