Human Body
The machine that is the human body is so dependable, so familiar that we are often
surprised at its amazing inner complexity. Bone, fluids, muscle, skin and all the other
parts are constructed of cells. Brain cells remember. They react to information, to
stimuli, then send electrical commands through nerve cells to muscle cells: constrict!
As you are reading these words with the cells in your eyes, please pause and lift your
right index finger and touch the tip of your nose. Notice the smoothness of operation.
Millions of cells in your body participated smoothly in that motion. Each of us is an
electrochemical machine -- animal -- being -- composed of cells. What gives life to our
cells?
Your left hand
Please bring your left hand closer to your eyes. Focus on the tiny lines of your skin.
The lines are valleys, separating broad, pliable plateaus. Skin cells form a rather thin
covering around our wet muscles, bones, nerves and tubes made of cells. On your
hand, can you see blood vessels beneath your skin? What are you made of?
Cell workings
The building blocks of your body are small masses of protoplasm bounded by a membrane.
Cells are the fundamental units of any living organism. It is a busy, watery place inside a
cell. Virtually every cell in your body contains a complete copy of your genome, the genetic
material of you as an organism.
Imagine the genome as the United States. Each chromosome is a different state. As many as
100,000 genes are the cities and towns.
Organizing genes
A chromosome is a small package of genes in the nucleus of a cell. Different kinds of
organisms have different numbers of chromosomes. Homo sapiens have 23 pairs of
chromosomes, 46 in all, including two sex chromosomes. In mating, each parent contributes
one chromosome to each pair, so a child gets half of his chromosomes from his mother and
half from his father.
Files of fate
Much about your life, your proclivity for mental or physical ailments, the color of your eyes,
is determined inside your chromosomes. A human chromosome is extremely small. But it
may contain a string of DNA 2.8 inches (7 centimeters) long -- perhaps as long as your little
finger!
The importance of proteins
A gene, which is a length of the DNA double helix, is a unit of heredity, passed from parent
to offspring. Genes are pieces of DNA, and most genes contain the formula for making a
specific protein. Not much happens in our bodies without proteins. They labor inside cells and
perform many jobs, working as enzymes, hormones, antibodies. Each protein is the product
of a particular gene.
Designer kid?
The encircling structure is made of sugar and phosphate. Like a twisting ladder, the famous
double helix holds the recipe for life itself. The rungs of the DNA ladder are made of four
chemicals known by the letters A, T, G and C. They come in pairs and spell the words, give the
commands. Human beings have about 3.2 billion pairs.
As we expand our knowledge of how these codes control our bodies, our lives, scientists may be able to return sight to blind eyes, may be able to give you a "designer kid." How tall, how smart? How much money would you pay to give your child an additional 50 I.Q. points?