Genomic Imprinting Disorders Flashcards
What is androgenesis?
Development of an embryo containing only paternal chromosomes.
What is parthenogenesis?
Reproduction by development of an unfertilized female gamete.
-e.g. gecko
What is a hydatidiform mole?
Mass of tissue in womb that won’t develop into a baby.
- androgenetic (usually 46, XX)
- false pregnancy
What is a potential complication of a hydatidiform mole?
Can develop into malignant trophoblastic tumour.
What can parthenogenesis cause?
Benign ovarian teratomas.
- from oocytes than have complete 1st/both meiotic divisions
- predominantly epithelial tissue
Are androgenesis and parthenogenesis viable?
Not in humans.
-even though there’s a normal chromosome number
Why do pathenogenesis embryos die?
Due to failure of development of extraembryonic structures.
-e.g. trophoblast, yolk sac
Why do androgenetic embryos die?
Poor embryo development.
-well developed extra-embryonic membranes
What stage do androgenetic embryos die at?
6 somite stage.
What is genomic imprinting?
Certain genes are expressed in a parent-of-origin specific manner.
-if a gene is imprinted, it’s silenced (epigenetic)
What are the main features of angelman syndrome?
- Facial dysmorphism (smiling)
- Mental disability
- Seizures
What are the main features of Prader-Willi syndrome?
- Hypotonia
- Mental disability
- Hypogenitalism
- Hyperphagia (obesity)
How are Angelman syndrome and Prader-Willi syndrome linked genetically?
Both due to deletion on chromosome 15 (q11-13).
- always de novo
- UBE3A gene
What is the genetic difference between Angelman syndrome and Prader-Willi syndrome?
Angelman is due to maternal chromosome deletion.
Prader-Willi is due to paternal chromosome deletion.
What is DNA methylation?
Epigenetic mechanism to control gene expression.
- CH3 added to cytosine
- doesn’t normally alter DNA sequence
