The two basic parts of the tumbled pebble and the arrowhead we considered are hard and soft rock. Two basic parts of every living system are DNA and protein. DNA is the famous molecule of heredity. It's a focus of crime scene investigations, and we often hear news stories about it. This is the molecule that gets passed down from one generation to the next. Each of us starts oﬀ as a tiny little ball about the size of a period on a printed page. In that tiny ball, there are over six feet (2m) of DNA all coiled up. All of our physical characteristics (height, skin color, etc.) are "spelled out" in that DNA.
What are proteins? Proteins are the molecules of structure and function. Hair is mostly protein; skin cells are packed full of proteins; the enzymes that break down food and build it up are proteins; the filaments that slide together to make muscles work are proteins.
So DNA and protein are two basic "parts" of every living system. When you get down to a virus, that's all you find — DNA and protein. (In some viruses, RNA substitutes for DNA.) The DNA molecules code for the protein molecules that make us what we are. That same principle applies to all life forms: viruses, plants, and animals, as well as human beings.
My students study all of the details, but DNA and protein molecules are really quite simple in their basic structure. If you can picture a string of pearls, you can picture DNA: it is a chain of repeating units. Figure 2-A [shown in original article] is a diagram of a DNA molecule. The parts that look like railroad boxcars are sugar and phosphate groups, and the parts that stick out from each boxcar in the chain are groups called bases.
Proteins are built in about the same way. Proteins are also chains of repeated units. As shown in Figure 2-B, the links in protein chains are called amino acids. In all living things, inherited chains of DNA bases are used to line up chains of amino acids. These amino acid chains are the protein molecules responsible for structure and function. For example, chains of several hundred DNA bases tell the cell how to make a protein called hemoglobin, and that protein functions as the oxygen carrier in red blood cells. In short form, DNA → protein → trait, and that relationship is the physical basis of all life on earth.
Now, what about that relationship between DNA and protein? How did it get started? Evolutionists picture a time long ago when the earth might have been quite diﬀerent. They imagine that fragments of DNA and fragments of protein are produced. These molecules are supposed to "do what comes naturally" over vast periods of time. What’s going to happen? Will time, chance, and chemical reactions between DNA and protein automatically produce life?