Genetics
1p36 Deletion Syndrome is a congenital genetic disorder caused by the deletion of the most distal light band of the short arm of chromosome 1. Chromosome 1 is the largest human chromosome and represents about 8 percent of the total DNA in human cells. The "p" stands for the short or 'petite' arm of the chromosome. '36' stands for the location of the deletion on the chromosome.
The breakpoints for 1p36 Deletion Syndrome have been variable and are most commonly found from 1p36.13 to 1p36.33. 40 percent of all breakpoints occur 3 to 5 million base pairs from the telomere. The size of the deletion ranges from approximately 1.5 million base pairs to greater than 10 million. Studies have suggested that the larger the deletion, the more severe the symptoms exhibited in the individual, but this has not been proven definitively.
Most deletions in chromosome 1p36 are new mutations, that occur before fertilization, during the formation of gametes (eggs or sperm). There have also been reports of patients with 1p36 deletion syndrome whose parents have a balanced or symmetrical translocation. This means a portion of one chromosome is transferred to another chromosome, so the parent has the "36" portion of chromosome 1 attached in an alternate location. When this occurs, cell division creates gametes that are missing a piece of 36.
In new mutations, the mechanism causing chromosome breakage is unknown. Deletions of paternal origin (father) are larger than the deletions deriving from the maternal (mother) chromosome. The majority of deletions are maternally derived. There do not seem to be differences in the clinical manifestations (the symptoms or observable conditions which are seen as a result of 1p36) based on whether the deletion is on the paternal or maternal chromosome.
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