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
Transient neonatal diabetes
UPD 14 mat/pat
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
Trisomy rescue ****
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
Bisulphate modification methods: MS-PCR, PCR & restriction analysis, melts curve analysis, pyrosequencing