Rv. Samonte et al., MOLECULAR CYTOGENETIC CHARACTERIZATION OF BREAKPOINTS INVOLVING PERICENTRIC INVERSIONS OF HUMAN-CHROMOSOME-9, Human genetics, 98(5), 1996, pp. 576-580
Pericentric inversions involving the secondary constriction (qh) regio
n of chromosome 9 are considered to be normal variants. The evolutiona
ry mechanisms and conservation of these inversions via Mendelian fashi
on have been investigated since the advent of banding techniques. Rout
ine cytogenetic techniques cannot provide the fine characterization ne
cessary to determine the type of genetic material involved in these re
arrangements. Therefore, the fluorescence in situ hybridization techni
que with the human centromere-specific alpha satellite and the beta sa
tellite (D9Z5) and classical satellite (D9Z1) human DNA probes were us
ed to identify the breakpoints of chromosome 9 pericentric inversions.
Four unique types of pericentric inversions involving the 9qh region
were observed, and the mechanism may be due to breakage and reunion at
the proposed breakpoints. They are: type A inversions consist of brea
kpoints within the alpha and beta satellite DNA regions; type B consis
t of breakpoints within the beta satellite DNA region and band 9q13; t
ype C involve breakage within the beta and classical satellite DNA reg
ions, and type D have breakpoints within the alpha and classical satel
lite DNA regions. Obviously, reshuffling of satellite DNA sequences ha
s occurred, which has given rise to a variety of heteromorphisms whose
clinical significance remains obscure.