Chromosome

Abnormalities

Changes in chromosomal structure

Chromosomal changes can occur spontaneously or from radiation or exposure to certain chemicals

There are four means of chromosomal changes:

DeletionIn deletion, part of the chromosome is actually lost. Viruses, radiation and chemicals can cause a piece of a chromosome to become dislocated.

This piece may carry a specific gene which may have a large effect on the host.

Cri-du-chatMissing piece of chromosome 5Causes an abnormally developed larynxAffected infants cries sound like the mewing of a cat

DuplicationIn duplication, a gene sequence is repeated one or more times within a chromosome

At some point, too many repeats can affect the function of the gene

Fragile X SyndromeA specific sequence on chromosome X, normally repeated 29 times, is repeated 700 times!

Most common cause of autism

InversionIn inversion, a gene segment momentarily becomes free from its chromosome and then reinserts in the opposite order.

This can completely alter the gene’s activities

TranslocationIn translocation, part of a chromosome changes place with another part of either the same or a non-homologous chromosome.

Translocation can result in some cancers, Down Syndrome, and leukemia

Translocation and Disease

Linked to:CancerInfertility: Down syndrome