Chromosome Polymorphism and Human Pathology: About 27 Cases of Chromosome 9 Inversion in the Beninese Population
Simon AzonbakinAlfred OuedraogoAlexis OuedraogoDaniel SewadounoArnaud AgbanlinsouYannick GoussanouMarius AdjagbaJules AlaoAnatole Lalèyè
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Abstract:
The chromosomal polymorphism defined by variations of some chromosomal regions of a person (the constitutive heterochromatin and the short arms of the acrocentric chromosomes (13 to 15 and 21 - 22)) sometimes highlighted problems with regard to their safety and their pathogenicity. Polymorphisms are usually found in the same family and transmitted in the dominant Mendelian. Chromosome 9 inversion is a frequent phenomenon that some cytogeneticists consider as a variant of normal. Despite its classification as a minor chromosome rearrangement which does not correspond to abnormal phenotypes, many reports have raised conflicting opinions as well, and its complete safety is controversial. 27 cases of inversion of chromosome 9 were identified in our laboratory. The main indications for karyotype of the case of inv (9) were congenital cardiopathy (18.5%), sex development disorders of (18.5%), down syndrome (18.5%), and infertility (14.8%). This study stood out the observations of many authors who highlighted the involvement of inv (9) in the genesis of several pathologies.Keywords:
Mendelian inheritance
Chromosomal rearrangement
Chromosomal inversion
Chromosomal inversion
Breakpoint
Chromosomal rearrangement
Gene rearrangement
Derivative chromosome
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Chromosomal inversion
Chromosomal rearrangement
Chromosome 9
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Chromosomal inversion
Chromosomal rearrangement
Hominidae
Euchromatin
Pongidae
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Chromosomal inversion
Reversion
Chromosomal rearrangement
Gene rearrangement
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Chromosomal rearrangement
Chromosomal inversion
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INVERSIONS ARE INTRACHROMOSOMAL structural rearrangements. The commonest is the simple (or single) inversion. If the inversion coexists with another rearrangement in the same chromosome, it is a complex inversion. The simple inversion comprises a two-break event involving just one chromosome. The intercalary segment rotates 180°, reinserts, and the breaks unite (Fig. 9–1). The rearranged chromosome consists of a central inverted segment, and flanking distal, or noninverted segments. If the inverted segment includes the centromere, the inversion is pericentric; if it does not, it is paracentric. Figure 9–2 depicts two different pericentric inversions of chromosome 3. Note that the pericentric inversion has one break in the short arm and one in the long arm, whereas in the paracentric inversion both breaks occur in the same arm. Thus, when reading cytogenetic nomenclature, one can readily tell which is which: for example, 46,XX,inv(3)(p25q21) is pericentric and 46,XY,inv(11)(q21q23) is paracentric (inv = inversion). The clinical relevance of inversion chromosomes is that they can set the stage for the generation of recombinant (rec) gametes that may lead to abnormal pregnancy.The heterozygote is, other things being equal, a phenotypically normal person. The reorientation of a sequence of genetic material apparently does not influence its function, and breakage and reunion at most sites do not perturb the smooth running of the genome. Some inversions of the X may be an exception to this rule: a breakpoint involving the X long arm within the “critical region” can cause gonadal insufficiency. Some pericentric breakpoints occur at preferential sites, including 2p13, 2q21, 5q13, 5q31, 6q21, 10q22, and 12q13 (Kleczkowska et al., 1987); and certain paracentric breakpoints are likewise overrepresented (Madan, 1995).
Chromosomal inversion
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Chromosomal rearrangement
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A constitutional chromosome rearrangement in a phenotypically normal male orangutan is described. The rearrangement resulted from three breakages in chromosome 9 and involved a pericentric inversion and additional reciprocal transpositions of the terminal segments of both arms. Q-, G-, and C-banding studies were carried out, and it was shown that the chromosome affected was a member of the only pair in the complement that lacked a centromeric C-band and that its G-banding pattern closely resembled that of chromosome 12 in man. The origin of the rearrangement and the role of such rearrangements in producing chromosome polymorphisms are discussed, particularly in relation to evolution and speciation. An additional pair of heteromorphic chromosomes (No. 23) is also described. The short arm satellited region of one member of the pair was found to be variable and strongly C-banded.
Chromosomal inversion
Chromosomal rearrangement
Gene rearrangement
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Chromosomal inversion
Breakpoint
Chromosomal rearrangement
Chromosome 9
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Chromosomal rearrangement
Chromosomal inversion
Breakpoint
Cleidocranial Dysplasia
Comparative genomic hybridization
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Summary The mouse mutation hairy ears ( Eh ) originated in a neutron irradiation experiment at Oak Ridge National Laboratory. Subsequent linkage studies with Eh and other loci on Chr 15 suggested that it is associated with a chromosomal rearrangement that inhibits recombination since it shows tight linkage with several loci occupying the region extending from congenital goiter ( cog ) distal to caracul ( ca ). We report here (1) linkage experiments confirming this effect on recombination and (2) meiotic and mitotic cytological studies that confirm the presence of a chromosomal rearrangement. The data are consistent with the hypothesis of a paracentric inversion in the distal half of Chr 15. The effect of the inversion extends over a minimum of 30 cM, taking into account the genetic data and the cytologically determined chromosomal involvement extending to the region of the telomere.
Chromosomal inversion
Chromosomal rearrangement
Chromosomal crossover
Genetic linkage
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