"Forming an embryo is the hardest thing you will ever do."
[Gilbert, 2000]
[Slide 1 Making of a Baby 1 PPT]
The prodigious task of the embryo as it labors to continuously remold itself on the fly up to the moment it emerges from the womb is surely one of the most phenomenal undertakings in the universe. Hidden by the womb, the embryo constructs all of its body parts using a molecular toolkit that is far too small to observe with the naked eye. The complexity of its task is likely unrivaled on earth.
The embryo, however, is not left to do it all entirely on its own. The mother, in addition to providing the essential building blocks to make fats, sugars, and proteins, has also carefully stocked the maternal egg with “messages”, as it were, which contain the instructions for making the first proteins, several of which in turn will be used to generate the next set of recipes.
These messages are in the form of messenger RNA (mRNA). The messages themselves are copied from the “Book of Life” which is encoded in the DNA [Slide 5 DNA-Primer-PPT-03]. We can think of the DNA as a library, with each book representing one of the genes from which proteins are ultimately made.{See: "It’s a DNA World Baby" for details.}
The set of messages that the mother has bequeathed to the single-celled zygote, the outcome of its parents desire, is enough to initiate within the zygote a process that will eventually lead to an adult human, a complex being possessing 100 trillion cells. If this is not a miracle, it is hard to fathom what qualifies. Despite this, expectant parents have good reason to believe their child will be born healthy.
These mRNA’s are provided by nurse cells, which “attend” the eggs much like servants in a queen’s retinue.[Slide here] Already in the egg at the time of fertilization are the instructions for determining the axial polarities of the future embryo which will determine where the head and tail will go, where the spinal cord and gut will go, where the heart and liver will go. Surprisingly few genes make the decisions that will specify the body plan axes for all bilateral organisms – from fruit fly to human. While there are differences between fruit fly and man they are largely just variations on a master plan for development of bilateral organisms formulated over 500 million years ago. So “thoroughly modern man” may not be so modern after all. We shall see time and again how the embryos of man and his fellow mammals use the same basic molecular tool kit to fashion themselves, surely evidence of the oneness of life on earth.
