Formation of a<unk>  chromosome<unk>  is caused by a<unk>  chromosome, a form of chromosome mutation where the ends of a chromosome lose genetic material and attach to one another, forming a<unk>  is one of the acrocentric chromosomes, meaning the short arm is unusually small and lacks genes relevant to development; accordingly, the phenotype of<unk>  is caused only by the loss of genes in the long arm. The amount of genes lost in a deletion can vary significantly, with reports of the loss of anywhere between 0.15% and 21% of chromosome<unk>  in different symptomatic cases.<unk>  chromosomes virtually always arise sporadically, with few documented cases of parent-to-child transmission. Due to the inherent instability of<unk>  chromosomes, inheritance is uncommon even with affected parents. However, cases have been reported of intergenerational inheritance of<unk> . Significant overlap exists between the phenotype of<unk>  and that of Phelan-McDermid syndrome, another chromosome<unk>  deletion syndrome. This is ascribed to a shared deletion of the SHANK3 gene at<unk> q13.3. Reports exist of people with<unk> <unk>  who lack the SHANK3 deletion and have normal phenotypes, marking SHANK3 as a critical region for the<unk>  syndrome.
Ring chromosome 22
Ring chromosome 15
Ring chromosome 18
X chromosome
Y chromosome
Dup15q
Distal 18q-
Ethosome