A novel mechanism for the origin of supernumerary marker chromosomes.
A ring chromosome 3 and a 47th chromosome formed by the portions of 3p and 3q distal to the r(3) breakpoints were found in a girl with mental retardation and minor facial anomalies. The supernumerary chromosome 3, rea(3), had a primary constriction inside its 3p portion (3p23) and was consistently stable both in lymphocytes and fibroblasts. In situ hybridization with alphoid probes revealed that the r(3) maintained its wild-type-centromere, whereas the rea(3) showed no alphoid-related signals. This case and a similar one recently reported demonstrate that acentric fragments can acquire a new centromere and become stable, and that supernumerary marker chromosomes can also originate by the junction of the acentric portions distal to the centric region forming a ring. The possibility of such a chromosome segregating will depend on its ability to (re)activate a new centromere.
Maraschio
P
P
Biologia Generale e Genetica Medica, Università di Pavia, Italy.
Tupler
R
R
Rossi
E
E
Barbierato
L
L
Uccellatore
F
F
Rocchi
M
M
Zuffardi
O
O
Fraccaro
M
M
D000328:Adult; D002869:Chromosome Aberrations; D025063:Chromosome Disorders; D002874:Chromosome Mapping; D002893:Chromosomes, Human, Pair 3 / Q000235:genetics*; D005145:Face / Q000002:abnormalities; D005260:Female; D005819:Genetic Markers; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008607:Intellectual Disability / Q000235:genetics; D007621:Karyotyping; D000091402:Prohibitins; D012303:Ring Chromosomes
D005819:Genetic Markers; C000717331:PHB2 protein, human; D000091402:Prohibitins