2. A recurring theme in human reproduction derived from outcome results from lit

Question

2. A recurring theme in human reproduction derived from outcome results from literally millions of IVF treatments is that the developmental fate of the embryo, i.e., whether it will progress to a normal birth, is largely determined (i) in the oocyte before fertilization, (ii) at fertilization, or (iii) by the 8-cell stage. Considering the discussions in class and from the assigned readings, what specific molecular, cellular, and genetic processes or events occurring at the level of the plasma membrane, cytoplasm or DNA need to occur: (a) at each of these three stages in order to promote normal and successful embryogenesis (10) (b) what specific dysfunction(s) at each of these three stages have been shown to cause embryogenesis to fail and why? (10)

Explanation / Answer

(a) There are three stages of embryogenesis which involves the unfertilized ovum, sperm and fertilization of the ovum by the sperm. The ovum is surrounded by corona radiata and zona pellucida layers with a small pore for the entry of the sperm cell with an acrosome containing enzymes for digesting the layers of the female ovum membrane. The sperm cell then enters the inside of the cell and fertilizes the egg. There are various stages in the cell with unequal division of the cells leading to the formation of morula, blastula and gastrula stages with the increase in the number of cells in each stage from 2 cell, 4 cell,8 cell, 16 cell and 32 cell stage following cell division. There was a clover shape for the formation of the fertilized cells after division which are used for transplantation in the surrogate mother. These are the stages of multi-nucleation and cell division with formation of large number of cells with replication of the DNA inside the cell.

(b) The events which lead to the failure during invitro fertilization include:

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