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American College of Medical Genetics statement of diagnostic testing for uniparental disomy.

Shaffer LG, Agan N, Goldberg JD, Ledbetter DH, Longshore JW, Cassidy SB - Genet. Med. (2001 May-Jun)

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.

ABSTRACT

Chromosomes of known clinical relevance include 6, 7, 11, 14, and 15.

patients presenting with prenatally detected mosaicism or Robertsonian translocations for clinically relevant chromosomes.

patients presenting with features of disorders known to be associated with UPD.

patients presenting with features of disorders known to be associated with UPD.

Testing should be performed on DNA collected from the mother, father, and child/fetus using polymorphic markers.

Reporting of results includes at least two fully informative markers from each chromosome of interest and reported using the ISCN 1995 guidelines.17

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Related in: MedlinePlus

Common mechanisms resulting in uniparental disomy involving acrocentric chromosomal rearrangements. (a) Trisomy rescue of a trisomy conceptus from a Robertsonian translocation carrier results theoretically in UPD in 50% of cases. Since the non-disjunction must occur in meiosis I, the resulting UPD would be heterodisomic. (b) Monosomy rescue of a monosomic conceptus resulting from meiosis I nondisjunction and fertilization of a isomic gamete. Duplication (through isochromosome formation) of the only copy of a homologue would result in isodisomy in 100% of cases. Since the majority of nondisjunction occurs in maternal meiosis, most cases of isochromosomes arising through this mechanism would result in paternal isodisomy.
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f2-acmg_upd: Common mechanisms resulting in uniparental disomy involving acrocentric chromosomal rearrangements. (a) Trisomy rescue of a trisomy conceptus from a Robertsonian translocation carrier results theoretically in UPD in 50% of cases. Since the non-disjunction must occur in meiosis I, the resulting UPD would be heterodisomic. (b) Monosomy rescue of a monosomic conceptus resulting from meiosis I nondisjunction and fertilization of a isomic gamete. Duplication (through isochromosome formation) of the only copy of a homologue would result in isodisomy in 100% of cases. Since the majority of nondisjunction occurs in maternal meiosis, most cases of isochromosomes arising through this mechanism would result in paternal isodisomy.

Mentions: UPD arises usually from the failure of the two members of a chromosome pair to separate properly into two daughter cells during meiosis in the parent’s germline (nondisjunction). The resulting abnormal gametes contain either two copies of a chromosome (disomic) or no copy of that chromosome (isomic), instead of the normal single copy of each chromosome (haploid). This leads to a conception with either three copies of one chromosome (trisomy) or a single copy of a chromosome (monosomy). If a second event occurs by either the loss of one of the extra chromosomes in a trisomy or the duplication of the single chromosome in a monosomy, the karyotypically normal cell may have a growth advantage as compared to the aneuploid cells. UPD results primarily from one of these “rescue” events2 (Fig. 1). Other mechanisms can also lead to UPD, including a postfertilization error (via somatic recombination or gene conversion), gametic complementation, and somatic replacement of a derivative chromosome.3,4 These mechanisms, with the exception of a postfertilization error, will result in UPD of the entire chromosome (holochromosomic). Since the majority of nondisjunction occurs in maternal meiosis I,5 it is more likely for a trisomy to consist of two maternal chromosomes and one paternal chromosome. In this case, maternal UPD will result if the paternal chromosome is lost and the two maternal homologues are retained (Fig. 1a). Therefore, in a trisomy rescue, the ensuing UPD will most often result in heterodisomy (inheritance of the two different homologous chromosomes from one parent). Regions of isodisomy (homozygosity of contiguous loci) may result from meiotic recombination. Trisomy associated with Robertsonian translocations may also resolve to disomy through loss of a chromosome and would result in UPD in 50% of cases (Fig. 2a). The relatively rarer monosomy rescue through duplication of a chromosome during mitosis results in isodisomy for the whole chromosome (two identical homologues). Since most nondisjunction events occur during maternal meiosis I, rescue of a monosomic conceptus through chromosomal duplication (or isochromosome formation, see below) would be expected to result most often in paternal UPD (Figs. 1b and 2b).


American College of Medical Genetics statement of diagnostic testing for uniparental disomy.

Shaffer LG, Agan N, Goldberg JD, Ledbetter DH, Longshore JW, Cassidy SB - Genet. Med. (2001 May-Jun)

Common mechanisms resulting in uniparental disomy involving acrocentric chromosomal rearrangements. (a) Trisomy rescue of a trisomy conceptus from a Robertsonian translocation carrier results theoretically in UPD in 50% of cases. Since the non-disjunction must occur in meiosis I, the resulting UPD would be heterodisomic. (b) Monosomy rescue of a monosomic conceptus resulting from meiosis I nondisjunction and fertilization of a isomic gamete. Duplication (through isochromosome formation) of the only copy of a homologue would result in isodisomy in 100% of cases. Since the majority of nondisjunction occurs in maternal meiosis, most cases of isochromosomes arising through this mechanism would result in paternal isodisomy.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3111049&req=5

f2-acmg_upd: Common mechanisms resulting in uniparental disomy involving acrocentric chromosomal rearrangements. (a) Trisomy rescue of a trisomy conceptus from a Robertsonian translocation carrier results theoretically in UPD in 50% of cases. Since the non-disjunction must occur in meiosis I, the resulting UPD would be heterodisomic. (b) Monosomy rescue of a monosomic conceptus resulting from meiosis I nondisjunction and fertilization of a isomic gamete. Duplication (through isochromosome formation) of the only copy of a homologue would result in isodisomy in 100% of cases. Since the majority of nondisjunction occurs in maternal meiosis, most cases of isochromosomes arising through this mechanism would result in paternal isodisomy.
Mentions: UPD arises usually from the failure of the two members of a chromosome pair to separate properly into two daughter cells during meiosis in the parent’s germline (nondisjunction). The resulting abnormal gametes contain either two copies of a chromosome (disomic) or no copy of that chromosome (isomic), instead of the normal single copy of each chromosome (haploid). This leads to a conception with either three copies of one chromosome (trisomy) or a single copy of a chromosome (monosomy). If a second event occurs by either the loss of one of the extra chromosomes in a trisomy or the duplication of the single chromosome in a monosomy, the karyotypically normal cell may have a growth advantage as compared to the aneuploid cells. UPD results primarily from one of these “rescue” events2 (Fig. 1). Other mechanisms can also lead to UPD, including a postfertilization error (via somatic recombination or gene conversion), gametic complementation, and somatic replacement of a derivative chromosome.3,4 These mechanisms, with the exception of a postfertilization error, will result in UPD of the entire chromosome (holochromosomic). Since the majority of nondisjunction occurs in maternal meiosis I,5 it is more likely for a trisomy to consist of two maternal chromosomes and one paternal chromosome. In this case, maternal UPD will result if the paternal chromosome is lost and the two maternal homologues are retained (Fig. 1a). Therefore, in a trisomy rescue, the ensuing UPD will most often result in heterodisomy (inheritance of the two different homologous chromosomes from one parent). Regions of isodisomy (homozygosity of contiguous loci) may result from meiotic recombination. Trisomy associated with Robertsonian translocations may also resolve to disomy through loss of a chromosome and would result in UPD in 50% of cases (Fig. 2a). The relatively rarer monosomy rescue through duplication of a chromosome during mitosis results in isodisomy for the whole chromosome (two identical homologues). Since most nondisjunction events occur during maternal meiosis I, rescue of a monosomic conceptus through chromosomal duplication (or isochromosome formation, see below) would be expected to result most often in paternal UPD (Figs. 1b and 2b).

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.

ABSTRACT

Chromosomes of known clinical relevance include 6, 7, 11, 14, and 15.

patients presenting with prenatally detected mosaicism or Robertsonian translocations for clinically relevant chromosomes.

patients presenting with features of disorders known to be associated with UPD.

patients presenting with features of disorders known to be associated with UPD.

Testing should be performed on DNA collected from the mother, father, and child/fetus using polymorphic markers.

Reporting of results includes at least two fully informative markers from each chromosome of interest and reported using the ISCN 1995 guidelines.17

Show MeSH
Related in: MedlinePlus