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DiGeorge syndrome is typically due to the deletion of 30 to 40 genes in the middle of chromosome 22 at a location known as 22q11.2. [3] About 90% of cases occur due to a new mutation during early development, while 10% are inherited. [7] It is autosomal dominant, meaning that only one affected chromosome is needed for the condition to occur. [7]
The following conditions are caused by changes in the structure or number of copies of chromosome 22: 22q11.2 deletion syndrome: Most people with 22q11.2 deletion syndrome are missing about 3 million base pairs on one copy of chromosome 22 in each cell. The deletion occurs near the middle of the chromosome at a location designated as q11.2.
Alright as a quick recap, DiGeorge syndrome or 22q11.2 deletion syndrome, is a genetic condition where the q11.2 portion of DNA on chromosome 22 is deleted, which can cause developmental issues like thymic and parathyroid hypoplasia, congenital heart defects, facial abnormalities, mental health conditions, and others.
That is, a fragment of chromosome 11 is moved, or translocated, to chromosome 22. 22q11 deletion syndrome [2] is a rare condition which occurs in about one in 4000 births. This condition is identified when a band in the q11.2 section of the arm of chromosome 22 is missing or deleted.
22q11.2 distal deletion syndrome is a rare genetic condition caused by a tiny missing part of one of the body's 46 chromosomes – chromosome 22. 22q11.2 distal deletion syndrome appears to be a recurrent genomic disorder distinct from 22q11.2 deletion syndrome also known as DiGeorge syndrome (DGS; 188400) and velocardiofacial syndrome (VCFS; 192430).
[1] [2] Three chromosomal abnormalities with ISCN nomenclature, with increasing complexity: (A) A tumour karyotype in a male with loss of the Y chromosome, (B) Prader–Willi Syndrome i.e. deletion in the 15q11-q12 region and (C) an arbitrary karyotype that involves a variety of autosomal and allosomal abnormalities. [3]
In humans, chromosomes Y and 22 have the greatest proportion of SDs: 50.4% and 11.9% respectively. [2] SRGAP2 is an SD. Misalignment of LCRs during non-allelic homologous recombination (NAHR) [ 3 ] is an important mechanism underlying the chromosomal microdeletion disorders as well as their reciprocal duplication partners. [ 4 ]
Twins in Poland with 22q11 microdeletion syndrome. A microdeletion syndrome is a syndrome caused by a chromosomal deletion smaller than 5 million base pairs (5 Mb) spanning several genes that is too small to be detected by conventional cytogenetic methods or high resolution karyotyping (2–5 Mb).