Conservation of the X-Linkage Group in Toto by All Eutherian Mammals

Ohno, Susumu

doi:10.1016/b978-0-12-728960-1.50010-0

Cited by 3 publications

(3 citation statements)

References 27 publications

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“…The X chromosome has been largely conserved. Studies have indicated that genes on the long arm of the human X chromosome are especially conserved in all mammals, suggesting that this region was part of a n ancient mammalian X chromosome [Ohno, 1994;Watson et al, 19911. In contrast, the Y chromosome has undergone extensive changes and has been reduced substantially in its size. Indeed, the Y chromosomes of different primate species show variability.…”

mentioning

confidence: 99%

Phenotype/Karyotype correlations of Y chromosome aneuploidy with emphasis on structural aberrations in postnatally diagnosed cases

1994

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Over 600 cases with a Y aneuploidy (other than non-mosaic 47,XYY) were reviewed for phenotype/karyotype correlations. Except for 93 prenatally diagnosed cases of mosaicism 45,X/46,XY (79 cases), 45,X/47,XYY (8 cases), and 45,X/46,XY/47,XYY (6 cases), all other cases were ascertained postnatally. Special emphasis was placed on structural abnormalities. This review includes 11 cases of 46,XYp-; 90 cases of 46,XYq- (52 cases non-mosaic; 38 cases 45,X mosaic); 34 cases of 46,X,r(Y) (9 cases non-mosaic and 25 cases 45,X mosaic); 8 cases of 46,X,i(Yp) (4 non-mosaic and 4 mosaic with 45,X); 12 cases of 46,X,i(Yq) (7 non-mosaic and 5 mosaic); 44 cases of 46,X,idic(Yq); 80 cases of 46,X, idic(Yp) (74 cases had breakpoints at Yq11 and 6 cases had breakpoints at Yq12); 130 cases of Y/autosome translocations (50 cases with a Y/A reciprocal translocation, 20 cases of Y/A translocation in 45,X males, 60 cases of Y/DP or Y/Gp translocations); 52 cases of Y/X translocations [47 cases with der(X); 4 cases with der(Y), and 1 case with 45,X with a der(X)], 7 cases of Y/Y translocations; 151 postnatally diagnosed cases of 45,X/46,XY; 14 postnatally diagnosed cases of 45,X/47,XYY; 18 cases of 45,X/46,XY/47,XYY; and 93 aforementioned prenatally diagnosed cases with a 45,X cell line. It is clear that in the absence of a 45,X cell line, the presence of an entire Yp or a region of it including SRY would lead to a male phenotype in an individual with a Y aneuploidy, whereas the lack of Yp invariably leads to a female phenotype with typical or atypical Ullrich-Turner syndrome (UTS). Once there is a 45,X cell line, regardless of whether there is Yp, Yq, or both Yp and Yq, or even a free Y chromosome in other cell line, there is an increased chance for that individual to be a phenotypic female with UTS manifestations or to have ambiguous external genitalia. This review once again shows a major difference in reported phenotypes between postnatally and prenatally diagnosed cases of 45,X/46,XY, 45,X/47,XYY, and 45,X/46,XY/47,XYY mosaicism. It appears that ascertainment bias can explain the fact that all known patients with postnatal diagnosis are phenotypically abnormal, while over 90% of prenatally diagnosed cases are reported to have a normal male phenotype. Further elucidation of major Y genes and their clinical significance can be expected in the rapidly expanding gene mapping projects. More, consequently better, phenotype/karyotype correlations can be anticipated at both the cytogenetic and the molecular level.

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mentioning

confidence: 99%

Phenotype/Karyotype correlations of Y chromosome aneuploidy with emphasis on structural aberrations in postnatally diagnosed cases

1994

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“…These observations suggest occurrence in wood lemmings of a gene in Xp, rearrangement of which can block the normal function of the Y chromosome. But according to Ohno's law, a gene on the X chromosome in one eutherian mammal will be found on the X chromosome in all eutherian mammals (Ohno, 1994;1967). Occurrence of at least one Xlinked sex-reversing gene may thus be inferred in the human.…”

Section: The Scandinavian Wood Lemming: a Role Of The X Chromosome Inmentioning

confidence: 99%

X-linked sex-reversing genes

Wachtel

1998

Cytogenet Genome Res

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Rearrangement of the X chromosome generates fertile XY females in the wood lemming, and a duplication has been discovered in Xp21 in some XY females in the human. This has enabled identification and mapping of a novel sex-reversing gene in the human, double dosage of which blocks development of the testis. Whether or not the human gene is related to the gene that causes sex reversal in the wood lemming remains to be seen. Yet similar genes must exist in all eutherian mammals, according to Ohno’s Law.

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“…According to Ohno (1994), all placental mammals of today descended from a common stock of protoinsectivores that emerged at the dawn of the Cenozoic era. Extensive speciation from a common ancestor was accomplished without substantial change in the total DNA content, and almost exclusively by allelic mutation of individual gene loci, with little or no change in the total number of gene loci.…”

Section: Introductionmentioning

confidence: 99%

Late-replicating X-chromosome: replication patterns in mammalian females

Tunin

Otto

2002

Genet. Mol. Biol.

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The GTG-banding and 5-BrdU incorporation patterns of the late-replicating X-chromosome were studied in female dogs and cattle, and compared to human female patterns. The replication patterns of the short arm of the X-chromosomes did not show any difference between human, dog and cattle females. As to the long arm, some bands showed differences among the three studied species regarding the replication kinetics pattern. These differences were observed in a restricted region of the X-chromosome, delimited by Xq11 → q25 in humans, by Xq1 → q8 in dogs, and by Xq12 → q32 in cattle. In an attempt to find out if these differences in the replication kinetics could be a reflection of differences in the localization of genes in that region of the X-chromosome, we used the probe for the human androgen receptor gene (AR) localized at Xq12, which is in the region where we observed differences among the three studied species. We did not, however, observe hybridization signals. Our study goes on, using other human probes for genes located in the region Xq11 → Xq25.

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Conservation of the X-Linkage Group in Toto by All Eutherian Mammals

Cited by 3 publications

References 27 publications

Phenotype/Karyotype correlations of Y chromosome aneuploidy with emphasis on structural aberrations in postnatally diagnosed cases

Phenotype/Karyotype correlations of Y chromosome aneuploidy with emphasis on structural aberrations in postnatally diagnosed cases

X-linked sex-reversing genes

Late-replicating X-chromosome: replication patterns in mammalian females

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