Further characterization of 19 cases of rea(21q21q) and delineation as isochromosomes or Robertsonian translocations in Down syndrome.
We have used 9 conventional RFLPs and 6 dinucleotide repeat polymorphisms on chromosome 21q to demonstrate that 17 of 19 cases of rea(21q21q) were consistent with isochromosomes i(21q) with the remaining 2 being true Robertsonian translocations. Eight of the 17 isochromosomes were of maternal origin and 9 cases were paternally derived. The 2 Robertsonian translocations were both maternally derived. Of the 17 isochromosomes, 7 were dicentric [idic(21q)] and 10 were monocentric [i(21q)]. Both rob(21q21q) were monocentric. Our findings agree with those made in 17 previously published cases of rea(21q21q). The parental origins of the i(21q) were equally divided between maternal (n = 17) and paternal (n = 15) origins. All 4 true rob(21q21q) reported to date are of maternal origin. Collectively, it appears that most homologous rearrangements of chromosome 21 are isochromosomes and only a small proportion are consistent with true Robertsonian translocations.
Shaffer
L G
LG
Institute for Molecular Genetics, Baylor College of Medicine, Houston, Texas 77030.
McCaskill
C
C
Haller
V
V
Brown
J A
JA
Jackson-Cook
C K
CK
D000328:Adult; D002675:Child, Preschool; D002891:Chromosomes, Human, Pair 21; D004314:Down Syndrome / Q000235:genetics*; D005260:Female; D006801:Humans; D008297:Male; D010375:Pedigree; D012150:Polymorphism, Restriction Fragment Length; D000091402:Prohibitins; D014178:Translocation, Genetic