Early Embryogenesis Flashcards
When is the term zygote used?
When the oocyte has been fertilised
What are pronuceli?
They are the two haploid nuclei of the sperm and the egg before they fuse. The pro-nuclei can be seen on day 0.
What happens on day 1 post fertilisation?
2 cell stage embryo
Maternal genomic transcription
What happens on day 2 post fertilisation?
4 cell stage
Zygote genomic transcription begins
What happens on day 3 post fertilisation?
8 cell stage (blastomeres)
It is now described as a morula
What happens on day 4 post fertilisation?
Compacting morula. Tight junctions start to appear between the blastomeres.
Blastomeres start to loose their totipotency as they become polarised, they are now pluripotent
What happens on day 5 post fertilisation?
Inner cell mass and trophectoderm cells start to differentiate. Blastocele starts to form. It is now described as a blastocyst
What happens on day 6 post fertilisation?
The blastocyst hatches from the Zona Pellucida
What are blastomeres?
Individual cells within the embryo
Describe the name of the trophectoderm cells that sit next to the ICM?
Polar trophectoderm cells
Describe the name of the trophectoderm cells that line the blastocoele
Mural trophectoderm cells
Describe epigenetic modification and DNA methylation
Both the oocyte and the sperm have completentary methylation and gene expression determining whether RNA polymerase can bind or not and therefore whether the gene is switched on or off. This means that development cannot occur without fertilisation.
The blastocyst erases these markers, however the come back later in development
