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Genetic and Rare Diseases Information Center (GARD)

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Chromosome 1q21.1 duplication syndrome

Other Names for this Disease
  • 1q21.1 microduplication syndrome
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What causes chromosome 1q21.1 duplication syndrome?

Chromosome 1q21.1 duplication syndrome can occur sporadically (by chance) from a de novo mutation or can be inherited in an autosomal dominant manner from a parent that has the same duplication. When the condition occurs sporadically, it is caused by a random error during the formation of the egg or sperm cell, or during the early days after fertilization.[1] The duplication occurs when part of chromosome 1 is copied (duplicated) abnormally, resulting in the extra genetic material from the duplicated segment.[2] If the condition is inherited from a parent, it means that one of the parents also has the extra piece of genetic material. In these cases, the parent with the duplication has a 50% chance with each pregnancy to pass the duplication on to his/her child. The only way to know if it has been inherited from a parent is for the parents to have genetic testing. A parent with the duplication may not have any signs or symptoms. In both cases, nothing that either parent does, or does not do, can cause this syndrome to occur.

Individuals who are interested in genetic testing for themselves or family members should speak with a genetics professional.
Last updated: 8/15/2013

  1. 1q21.1 Microduplications. Unique. June 2011; Accessed 8/15/2013.
  2. Chromosomal duplication. Genetics Home Reference. August 12, 2013; Accessed 8/15/2013.