Hi Dr. Smith In a prior post you said that the dna of the sperm can impact the cellular division of the embryos? when exactly do the dna of the sperm come into play with an embryo, on day 1 , day 2 or day 3?
The sperm DNA does not come into play until Day 3 of development, upon the activation of the embryonic genome (i.e. when the embryo becomes its own genetic entity). From Day 0 - Day 3, the egg DNA and cytoplasm runs the show. If the embryo is to develop beyond the 8-cell stage, the sperm and egg DNA have to be intact and competent to direct continued growth. Excessive DNA fragmentation in the sperm and/or abnormalities in chromosome number (from the egg of the sperm) can lead to arrested development at this stage. This is why I believe it is important to wait until Day 5 to transfer only those embryos demonstrating continuing developmental competence (i.e. blastocyst stage).
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