Genomic Imprinting and Embryo Implantation Flashcards
What is genomic imprinting?
In some cells only the maternally derived alleles of certain genes are active whilst in other cells only the paternally derived alleles of certain genes are active
What is genomic imprinting thought to be a result of?
Differential methylation of DNA during gamete maturation.
Where are embryos implanted in mammals?
The uterine wall (endometrium).
What is a haemochorial placenta?
Where the placenta tissue is in direct contact with maternal blood, leading to highly efficient exchange of nutrients.
Even though embryo implanting is a semi-allograft, why is it not rejected by the immune system?
The trophoblast expresses MHCI rather than MHCII
What occurs during the implantation window?
Changing steroid levels prime the endometrial epithelium, resulting in a change of cell surface proteins and sugars, as well as suppression of mucin molecules.
What is the role of the syncytial trophoblast?
To invade the uterine epithelium to reach the underlying stroma, basal lamina, and maternal blood vessels.
What is trophoblast invasion dependent on and why?
Metalloproteinases, enzymes which digest the extracellular matrix of the stroma.
What is a hydatiform mole? What causes it?
A tumour of the trophoblast tissue, failure of the female/male pronucleus to divide so the progeny offspring if entirely paternally/maternally derived.
