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Chromosomal Aberrations

Advances In Chromosomal Analysis, Chromosomal Aberrations, Aneuploidy, Disorders Associated With Aneuploidy, Abnormalities Of Chromosomal StructureUnbalanced Chromosome Rearrangements

Chromosomal aberrations are abnormalities in the structure or number of chromosomes and are often responsible for genetic disorders. For more than a century, scientists have been fascinated by the study of human chromosomes. It was not until 1956, however, that it was determined that the actual diploid number of chromosomes in a human cell was forty-six (22 pairs of autosomes and two sex chromosomes make up the human genome). In 1959 two discoveries opened a new era of genetics. Jerome Lejeune, Marthe Gautier, and M. Raymond Turpin discovered the presence of an extra chromosome in Down syndrome patients. And C. E. Ford and his colleagues, P. A. Jacobs and J. A. Strong first observed sex chromosome anomalies in patients with sexual development disorders.

A rearrangement is considered unbalanced if it results in extra or missing information. Structural rearrangements may be caused by a number of factors including chemicals, some viral infections, and ionizing radiation. Because the complement of DNA or genetic material in the chromosomes is greater or less than the complement of DNA in a normal set of chromosomes, there is likely to be abnormal development.

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Medicine EncyclopediaGenetics in Medicine - Part 1