额外的小环状染色体。

Kaffe S, Kim H J, Hsu L Y, Brill C B, Hirschhorn K

J Med Genet. 1977 Dec;14(6):447-51. doi: 10.1136/jmg.14.6.447.

A supernumerary small ring chromosome was found in 30% of cultured peripheral leucocytes and 50% of skin fibroblasts in a 6-year-old boy with mild mental retardation and midline cleft palate. The extra chromosome appeared to carry a densely staining region on Giemsa banding. The banding patterns of the remaining 46 chromosomes were normal. C banding indicated that the ring chromosome contained mainly centromeric constitutive heterochromatin. Chromosome analysis of both parents showed normal karyotypes by both conventional and banding techniques; thus the origin of the ring chromosome could not be determined.

在一名患有轻度智力发育迟缓及正中腭裂的6岁男孩中，30%的培养外周血白细胞和50%的皮肤成纤维细胞中发现了一条额外的小环状染色体。这条额外的染色体在吉姆萨染色带型上显示有一个浓染区。其余46条染色体的带型正常。C带显示环状染色体主要包含着丝粒组成型异染色质。对父母双方进行染色体分析，通过常规和带型技术均显示核型正常；因此，环状染色体的起源无法确定。