Yb. Yurov et al., ANALYSIS OF PERICENTROMERIC CHROMOSOME-21 SPECIFIC YAC CLONES BY FISH- IDENTIFICATION OF NEW MARKERS FOR MOLECULAR-CYTOGENETIC APPLICATION, Human genetics, 95(3), 1995, pp. 287-292
Fluorescence in situ hybridization (FISH) of chromosome 21 specific ye
ast artificial chromosome (YAC) clones after Alu-PCR (polymerase chain
reaction) amplification has been used to find new region-specific DNA
probes for the heterochromatic region of chromosome 21. Six overlappi
ng YAC clones from a pericentromeric contig map (region 21cen-21q11) w
ere analyzed. Four YAC clones were characterized as hybridizing to sev
eral chromosomal locations. They are, therefore, either chimeric or sh
ared by different chromosomes. Two of them containing alphoid satellit
e DNA, are localized at the centromeric regions of chromosomes 13 and
21 (clone 243A11), and on 13cen, 21cen and 1q3 (clone 781G5); the two
others are localized at both 21q11 and 13q2 (clone 759D3), and at 18p
(clone 770B3). Two YACs were strongly specific for chromosome 21qll on
ly (clones 124A7 and 881D2). These YACs were used effectively as probe
s for identifications of chromosome 21 during metaphase and interphase
analysis of 12 individuals, including three families with Down syndro
me offspring, and 6 amniocyte samples. The location of YAC clones on 2
1q11 close to the centromeric region allows the application of these c
lones as molecular probes for the analysis of marker chromosomes with
partial deletions of the long arm as well as for pre- and postnatal di
agnosis of trisomy 21 when alphoid or more distal region-specific DNA
probes are uninformative. Overlapping YAC clones covering human chromo
some 21q may be systematically used to detect a set of band-specific D
NA probes for molecular-cytogenetic application.