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Flashcards in UPD Deck (13):

What mechanisms can cause an imprinting disorder

1) UPD of imprinted region.
2) Deletion: del of gene or del of ICR
3) Duplication: ↑ expression of imprinted genes
4) Mutation on active allele
5) Epimutation: hypomethylation / hypermethylation @ ICR alters expression of imprinted gene.


Name 2 imprinting disorders

Beckwith weideman
Russell silver
Transient neonatal diabetes
UPD 14 mat/pat
UPD 20


What causes a complete hydatidiform mole

UPDpat diploid complement


What causes a partial hydatidiform mole

triploidy (46 of pat origin)


What's causes a benign cystic ovarian teratoma

UPDmat diploid complement


What disorder is associated with a segmental UPD

Beckwith weideman 15-20% cases


For carrier of structural rearr, rob, reciprocal translocation what are the mechanisms that cause a risk of UPD

postzygotic correction of an interchange trisomy.
monosomy rescue of monosomy from a 3:1 segregation
Acrocentric chrom isochrom formation.


What are the mechanisms for complete chromosome UPD

Gamete complementation
Trisomy rescue ****
Monotony rescue
Mitotic error


Describe gamete complementation

Mitotic NDJ in both parents results in a disomic gamete from one parent & a nullisomic gamete for the same chrom from the other parent.

result in a diploid zygote with UPHD


Describe trisomy rescue

Mitotic NJD in one parent results in a disomic gamete.
Fertilisation of a haploid gamete results in a trisomic conceptus.

Rescue͟ through loss of one homologue (perhaps anaphase lag)
at a very early postzygotic stage (poss in zygote)

UPD in 1/3 cases.
Meiosis I nondisjunction :UPHD
Meiosis II nondisjunction :UPID


Describe monosomy rescue

Meiotic NDJ results in a nullisomic gamete.
Fertilisation with a haploid gamete : monosomic conceptus.

Rescue͟ through mitotic NDJ/ mitotic misdivision leads to isochrom formation or duplication

In this case the UPD would be an isodisomy.


Name two different methods for detecting UPD

Methylation specific methods: Southern blotting, MLPA
Microsatellite analysis
Bisulphate modification methods: MS-PCR, PCR & restriction analysis, melts curve analysis, pyrosequencing
SNP array


What's an imprinting disorder

Disorder arising from the altered expression/function of an imprinted gene/ collection of genes