May 24, 2009
"The beginning of existence is one and the same for body and soul." ~Saint Gregory of Nyssa
Today was the first day of the summer session of teaching Anatomy and Physiology! My part time teaching experiences over the past academic year have shown me the career path on which I belong. Any one know of a college professor position opening up in about a year? :) The last lecture I gave for this past spring semester was on Human Development, probably my most favorite topic in biology. I had the opportunity to share my enthusiasm with my students by explaining this complex and, actually, quite holy topic. Not surprisingly, the few faces of positive amazement were balanced by the few students who uncharacteristically walked out before the lecture ended.... In earlier posts, I wrote much about marriage and how it is a path toward holiness. Included in the marriage sacrament of our Church are prayers for the granting of children to the newly-married couple. My friend and I counted the exact number of prayers during a wedding service last summer, and to be exact, in it there are 15 prayers for the couple to be granted children! Here, I'd like to write about some basic biology about how a new person comes into being. It appears that many of us are not acutely aware of the beautifully precise biology involved at the initiation of and during our own development in our mother's womb. Perhaps this may aid us in seeing the sanctity of human life more concretely and to witness to the truth within our present society that is seemingly blind to the image of God that the developing child bears at conception and throughout his or her development. In Saint John Chrysostom's homily, "On Christian Marriage", he speaks about St. Paul's Epistle to the Ephesians 5:28-33: "...the one flesh is, father, and mother, and the child from the substance of the two co-mingled. For indeed by the co-mingling of their seeds is the child produced, so that the three are one flesh." Biologically speaking, we can assign to the word "seed" here as either egg or sperm, or more specifically, the nucleus (this is the cellular structure that houses DNA) of either of these gametes. According to medical classification, conception begins after fertilization, when the DNA from the sperm combines (or co-mingles) with the DNA of the egg. The reason for this is that the result of this combination of maternal and paternal genetic material (each is composed of 23 chromosomes) is a brand new, and let me emphasize, UNIQUE and COMPLETE human genome (now containing the complete chromosome count of 46). At this point, there is no egg or sperm present, but a zygote (Gr. ζυγοτός, something yoked). The zygote is living and functional and will go on to become an embryo (Gr. έμβριο, to become fuller) and eventually a fetus (Lat., offspring). All of these words represent different developmental stages of human development. DNA is the genetic material which encodes all the characteristics of a person. As soon as the new zygote is formed, the next step is to replicate the new genome and to begin cell division. The picture above shows a newly-formed zygote with the two pro-nuclei from the gametes (egg or sperm) of each parent fusing. Please note that this occurs within the first day after fertilization has occurred through the physical union of two persons. Yes, it happens fast. Quoting the textbook I use for my course, Human Anatomy and Physiology (Marieb and Hoehn, 7th ed. 2007): "By providing the information for protein synthesis, DNA determines what type of organism you will be--frog, human, oak tree--and directs your growth and development." I love to laugh at some of these science textbook one-liners that ironically state the truth and reduce human dignity to the equivalent of amphibians and trees. This quote represents the scientific community's knowledge that DNA is responsible for determining human development, indicating that DNA is of great significance. Another couple of quotes are also particularly truthful regarding the cell theory: "...the cell is the smallest living unit." "..when you define cell properties, you are in fact defining the properties of life." These quotes indicate that individual cells are living entities. They contain DNA which directs their development and function. When we concentrate on the cells within a developing embryo, we see that those particular cells are no exception to the same cell theory. What makes the embryonic cells even more unique is that they each contain a completely NEW genome. Thus, we have in the embryo cells which are the smallest living units and they contain novel and unique genetic information which directs their development into a new human person. These observations point us to the direction that even scientists believe that life begins at conception--since at conception, a new genome is created and replicated as new embryonic cells divide and multiply to eventually form all the rudimentary structures of the human body by the 8th week after fertilization. In the next few posts, I hope to share more of my thoughts that intertwine biology and Christian faith in the context of human development. This will include topics on bioethics, particularly reproductive cloning and abortion. Your feedback is greatly welcome!