What are the genetic changes related to 1q21.1 microdeletion ?
Most people with a 1q21.1 microdeletion are missing a sequence of about 1.35 million DNA building blocks (base pairs), also written as 1.35 megabases (Mb), in the q21.1 region of chromosome 1. However, the exact size of the deleted region varies. This deletion affects one of the two copies of chromosome 1 in each cell.  The signs and symptoms that can result from a 1q21.1 microdeletion are probably related to the loss of several genes in this region. Researchers are working to determine which missing genes contribute to the specific features associated with the deletion. Because some people with a 1q21.1 microdeletion have no obvious related features, additional genetic or environmental factors are thought to be involved in the development of signs and symptoms.  Researchers sometimes refer to 1q21.1 microdeletion as the recurrent distal 1.35-Mb deletion to distinguish it from the genetic change that causes thrombocytopenia-absent radius syndrome (TAR syndrome). TAR syndrome results from the deletion of a different, smaller DNA segment in the chromosome 1q21.1 region near the area where the 1.35-Mb deletion occurs. The chromosomal change related to TAR syndrome is often called the 200-kb deletion.