The DNA “Blueprint”—An Exquisite Design
EACH of us begins life as a tiny single cell that some 20 years later yields a full-grown adult. From that one minuscule cell come all the various body parts: heart, stomach, liver and other internal organs; the intricate eyes and ears; the versatile fingers. Have you ever contemplated the sheer volume of information contained in that original single cell and its positively exquisite design?
Consider the following example. Suppose you needed to explain to someone who had never seen an automobile how to build one from raw materials. Each part, from the rearview mirror to the valves in the carburetor, must be described in every detail. Then you would have to explain how to manufacture and assemble these parts. Where do the spark plugs go? How is the steering wheel attached? All this information would have to be so precisely written that the reader could not possibly misunderstand. He must be able to build a complete and fully functional automobile by following your instructions to the letter. Imagine the number of pages of detailed instructions that it would take!
Now think again about that single human cell. The human body is far more complex than an automobile, yet, as the Bible says, “all its parts were down in writing.” (Psalm 139:16) The Creator has provided the entire blueprint in one tiny cell. Where does the cell store this huge amount of information?
All this information is found in a substance called DNA (deoxyribonucleic acid), most of which is located in a small compartment in the cell known as the nucleus. Human nuclei have 46 chromosomes. These chromosomes are essentially very long, thin strands of DNA. The strands are so long because all the needed information, contained in 3 to 4 million genes, is stored in the sequence of the DNA.
The Amazing DNA
The DNA is only about 0.00000008 inch (0.0000002 cm) wide. However, the total length of the DNA strands in a single human cell is 5 feet 8 1⁄2 inches (1.74 m). Each gene is a tiny section about 0.00001 inch (0.00003 cm) long. Imagine: all the information to make a complete human body is stored on strands less than 6 feet long and only 80 billionths of an inch wide!
Incredibly, this 5 feet 8 1⁄2 inches of DNA is contained in a nucleus that is only about 0.00004 inch (0.0001 cm) wide! We can more easily comprehend how amazing that is by visualizing the DNA as 600 times larger, a thread 0.024 inch (0.06 cm)—about 1⁄40 inch—wide. On this scale the nucleus would be a ball about a foot (30 cm) in diameter. This ball would contain lengths of thread totaling in all 330 miles (530 km)! To get an idea of the genetic complexity of the human body, picture yourself walking 330 miles and seeing a new gene every 5 inches.
A Packaging Problem
How is all this DNA packaged into the cell nucleus? Because the cell must be able to consult its “blueprint” by “reading” the genes along its DNA, these strands cannot simply be crammed into the tiny nuclear space. Even though there are so many long, thin strands, no strand can become tangled up in any other strand. The DNA is so neatly arranged that small sections of any strand can be quickly and easily “read” whenever necessary.
The DNA blueprint is vital to a cell. When a cell divides, each of the two new cells will need its own blueprint. This means that before a cell can divide, all the DNA must be copied to generate a duplicate set of genes. After the DNA has been carefully copied, the strands are coiled back and forth on themselves into very dense bundles. As the cell divides, these bundles are divided equally between the two new cells so that each receives an identical blueprint. Once inside the new cells, the bundles are uncoiled. All these manipulations are performed in such a meticulous manner that no sections of the strands—none of the vital genes—are accidentally knotted up, broken off or lost. Yet these processes occur inside a cell nucleus only a tiny fraction of the length of the DNA. What an extraordinary feat of design!
An Awesome Marvel
Many other features of the cell and its DNA remain a mystery to scientists. Adult humans have 90 to 100 different types of cells, each with a distinctive shape and size, and each specialized to perform a different task. Since almost every cell in the human body contains an identical copy of DNA strands, why do certain cells become skin cells and others become muscle, nerve or bone cells? In other words, how does the cell know which part of the DNA to “read” and when to “read” it?
Pondering over the cell and its DNA, we become awed by the creativity and intelligence of the One who designed this marvel, Jehovah God. As was Job, we are moved to say: “I have come to know that you are able to do all things, and there is no idea that is unattainable for you.”—Job 42:2.
[Picture on page 13]
Model of DNA molecule as proposed in 1953 by biologists Francis Crick and James Watson