In the late 1850’s, a humble, inconspicuous monk began to experiment with pea plants. Born Johann Mendel, he assumed the name Gregor upon entering the monastic life. He had twice failed the oral exam to become a certified high school teacher, but upon further education was eventually named the abbot at St. Thomas Abbey.
Mendel began to experiment with pea plants in an effort to understand how various traits were passed along in organisms. For a long time, it had been widely accepted that characteristics were transmitted via what was called blending inheritance. But by the early 1860’s, Mendel began to notice something different in the over 28,000 plants that he raised. Unlike previous ideas, he realized that traits were often inherited and expressed through dominant and recessive patterns. He published a paper in 1866 that largely went forgotten until the early 1900’s. But as 20th century scientists began to look deeper into what makes us, they discovered the brilliance of his findings, which eventually became the cornerstone of what we know today. He posthumously became known as the father of modern genetics, and today his findings constitute “Mendel’s Laws of Inheritance.”
Recently I found myself brushing up—or shall I say relearning—the basics of genetics as part of research for another series. As part of the sources I sought out, I went after the most rigorous I could find—Genetics for Dummies—which might as well have been called Rocket Science for Beginners. Fortunately, my friend Dr. Sabrina Mitchell, staff geneticist at Vanderbilt University, was also available to help me with the basics. In doing so, I was reminded of just how remarkably complex, brilliantly simple, and profoundly mysterious the genetic world is, and how science and divinity meet in some of the most extraordinary ways. For starters, consider a few of the basics:
All somatic cells, which are the cells that make up our body (e.g., skin cells, fat cells, liver cells), have a complete copy of the entire genome, which includes all of person’s genes. Even though your eye cells only divide to make more eye cells, they have a map for everything that is you. Some genes are expressed in nearly all tissues of the body, but certain genes are only expressed at specific points in development or in certain tissues. Consider that a drop of blood contains an average of 7,000 to 25,000 white blood cells in healthy humans (many more in those with cancer). Every single one of those cells has a copy of a person’s genome.
All human cells start out as totipotent, which means that they can form any type of cells. But around the point that the initial cell (from conception) has divided into 16 cells, these cells begin to diversify and eventually become nullipotent, forever to make only a specific type of cell. Interestingly, for females, it is also at this very time that one of the X-chromosomes (recall that females have two X chromosomes) in each cell becomes completely inactivated for life. Scientists are still trying to understand how and why this happens.
Despite the enormous complexity of our genome, DNA is actually rather uncomplicated. It is composed of a sugar and phosphate backbone and 4 nitrogen-containing bases: guanine, adenine, cytosine, and thymine. These bases form pairs through chemical bonds resulting in the double helix configuration of DNA. Of course, I should mention that humans have around 3 billion base pairs, all of which reside in our 46 chromosomes. Through the process of supercoiling, the DNA is tightly packed so that it fits into the cell nucleus. Just how tight? Well, all of the DNA from one cell in your body, laid end to end, would stretch approximately 6 feet. Considering you have around 100 trillion cells in your body, it means that the DNA from all your cells laid end to end would extend to the sun and back—almost 100 times. Interestingly, you and your neighbor share 99.999% of the exact same base pairs. In this case, it really is the .001% that makes the difference.
Think that’s amazing? Consider that DNA is both durable and replicable on a grand scale. DNA is a stable molecule and has been uncovered from organisms believed to have resided over 100,000 years ago. Furthermore, your body is constantly undergoing the process of making new DNA through mitosis, or cell replication. At any given time, your body is undergoing a DNA review process that makes the NY Times editorial board look like a kid’s coloring club. Despite an astonishing amount of DNA replication that occurs, there is an average of one error per 10 million base pairs after proofreading, and before the cleanup enzymes come through to do a final sweep.
One of the most incredible scientific accomplishments of the last century is the sequencing of the human genome. Scientists were surprised to find that less than 2% of the genome codes for proteins. This is much lower than what was estimated prior to mapping the human genome. The remaining 98% of the genome is packed with other functional elements, such as non-coding RNAs and specific DNA sequences that are important for regulating expression of genes and proteins, and may affect how the DNA is packaged. Efforts have been focused on uncovering these DNA elements to bring about a better understanding of how the human genome functions.
Most of us regularly look for signs or miracles in our daily life, and are drawn to unbelievable stories that defy any rational or scientific explanation. A few months ago, I was blessed to witness the miracle of our 7th child, Samuel Augustine, being born. All scientific explanations of how he came to be fall short of knowing him as a real person. But it strikes me that over 160 years ago, a quiet, Augustinian monk began to uncover the unseen miracle of everyday life through his persistence. So, whether or not you are a person of faith, the next time you are looking for something that seems too impossible to be true, look no further than the DNA inside. It certainly has given me another miraculous perspective on the miracle of our new baby boy.
