Contemplating Genetic Variability
Our previous post highlighted a unique animal—the eastern cicada killer wasp (phylum Arthropoda, order Hymenoptera, species Sphecius Speciosus). The post related some details of a recent family experience when our grandchildren encountered one of these wasps dragging its “kill” toward its underground burrow. It was an event to inspire admiration and respect from the grandfather and significant fear from some of the grandchildren. By coincidence, my pest service representative arrived a few days later for his regular visit to treat insect pests at our residence. Not knowing of our experience, he raised an unusual topic. Some of his customers a few doors away had just instructed him to “get rid of” cicada killer wasps inhabiting their property. This triggered a conversation and mutual agreement that generally, all wasps provide far more benefit than harm.
First-hand experience with neighborhood cicada killer wasps ignited other interesting discussions with friends. Some deeper discussions trended toward the genetic basis of morphology and unique behavior of these wasps. But what about the diversity of appearance and behavior in thousands of other species? Why do swarms of insects torment us in springtime? Or how does the last summer generation of beautiful Monarch butterflies know how to navigate to a tiny mountain forest site in southern Mexico? For observant, thoughtful, contemplative observers, morphology and behavior provide opportunities not only to describe, but also to explain the morphology and behavior of ALL living things in our neighborhood and on our planet. Description is easy; explanation is difficult!
We discuss a few highlights of the wonders of genetics. Examples below come from human genetics but our discussion concerning DNA, RNA, chromosomes, genes, proteins, codes, and codons applies to ALL living species. Genetics is an important topic in biology. From this term comes the more familiar exclamation, “It’s in my genes,” a term relating to one’s physical appearance or innate functional and behavioral traits. The popular statement “It’s in my DNA” is a take-off on the same expression. In the last seven decades our populace has been apprised of important details concerning the structure and function of the DNA molecule, thanks to the landmark discoveries of scientists James Watson and Francis Crick in the mid-20th century. Since then our knowledge of genetics has expanded exponentially.
Each of trillions of human cells in the human body contains 23 chromosomes located in the cell nucleus. Every chromosome is a “tightly wound” DNA molecule possessing numerous specific strands along its length. These key locations are termed genes—special segments of the magnificent DNA molecule. They are the ‘units of heredity’ on the DNA molecule. Why are they called units of heredity? Certain genes possess a “code” for the manufacture of proteins, the building blocks of one’s physical body. Protein building blocks are arranged in unique ways in each human body. We are able to observe living things as well as fellow human beings and make conclusions about their heredity. Their physical and behavioral characteristics were inherited, conferred to them from previous generations.
Altogether, there are about 20,000 genes distributed along human DNA molecules on 23 chromosomes. Lower numbered, larger chromosomes have more genes—specific segments of the entire DNA sequence of base pairs. For example, chromosome 1 has 2058 genes which “code for proteins.” Chromosome 22 has only 488 protein coding genes. In short, the protein coding mechanism relates to the sequence of chemical compounds (bases) arranged linearly on DNA and RNA molecules. A great majority of genes do not code for proteins, but they have many other important functions in living things.
DNA is found in the nucleus of almost all body cells. The DNA molecule must be transcribed to a similar chemical molecule called RNA and is re-located outside the nucleus in the cell’s cytoplasm. In cytoplasm the work of synthesizing and manufacturing proteins is accomplished. The sequence of four chemical bases on the strand of the RNA molecule (A, G, C, and U) may occur in many different ways. In the wisdom of the Creator, any three of these could occur randomly in any order just by chance. In God’s creative wisdom, however, twenty special combinations of three chemical bases code for each of twenty known amino acids, components of all proteins on Planet Earth. The combinations of three chemical uses are known as codons. The coding process is always the product of an intelligent mind.
The human body’s “building blocks” are really ‘proteins,’ sometimes lengthy chains of amino acids assembled in the cell’s cytoplasm from unique combinations of twenty amino acids. An array of protein building blocks is specific to each human on Earth. No two human beings are identical in appearance. (The exception is identical twins who share identical genetic traits.) Thousands of different proteins comprise each human body assembled in unique ways. Various estimates of the number of different proteins existing on our planet range far beyond one million. Humans possess tens of thousands of different proteins.
Our post has discussed only two living creatures—cicada killer wasps and humans! There are up to ten million separate species of living things on Planet Earth. The Creator of ALL Things has used the same template of life to create ALL living things.
We close with verses from Psalms which could apply to the wonder of living things “great and small,” from giant animals to humans to wasps to even tinier creatures. Only one of these living things is created imago dei (made in God’s image). We alone can learn and contemplate the beauty of God’s creative power and ability.
I praise you because I m fearfully and wonderfully made; your works are wonderful, I know that full well…..How precious to me are your thoughts, O God! How vast is the sum of them! Were I to count them, they would outnumber the grains of sand. (Psalm 139:14, 17-18 NIV)