Alex Gepneris, age 12, of Lethbridge, Alberta, Canada, for his question:
Where would you go to find a gene?
You might try peeking inside a living cell. Its nucleus would get lost inside a pinprick, but it is big enough to contain thousands of genes. If you view them through a super superior microscope, you might mistake them for bumpy strings of beads. Yet these tiny genes contain the blueprint that governs all the biochemical activities of the human body, including the traits and features that make it unique.
Scientists learned about the genes in easy stages. The investigation has been going on a long time and the final details still are shrouded in mystery. Actually, it began ages ago, when our ancestors realized that, though children tend to resemble their parents, each person is unique. This natural observation took a scientific turn when researchers traced the laws that govern a person's inherited characteristics from both sides of the family.
The next advance came when stronger microscopes vaguely revealed the outline and structure of the living cell. It is, of course, a small miracle of electro magnetic activity, encased in a thin membrane. The stuffing is a slightly jellified liquid, peppered with assorted granules. More or less in the center is the dense little nucleus. It holds the blueprint of all cellular activity and its orders are obeyed.
Powerful light microscopes reveal that the nucleus contains a number of small threads. When thin slices of tissue are stained for microscope slides, these come out in vivid color. Hence, they were named the chromosomes, meaning color bodies. There are 60,000 billion living cells, more or less, in a human body and the nucleus of each cell contains 46 chromosomes in 23 pairs. Light microscopes also reveal that each chromosome is a bumpy thread with about 1,250 little beads. These are the genes and the nucleus in every living cell in your body has about 57,000 of them.
At this point, researchers knew that the genes are inherited in equal numbers from both sides of the family. Each person inherits a unique pattern which is duplicated in every cell. Each gene governs certain biological functions and features and contains more items than a whole shelf of textbooks. The next breakthrough had to wait for the electron microscope and new skills in molecular biology. Then it was learned that the beady genes are wads of deoxyribonucleic acid the miraculous biochemical known as DNA.
Genes are present in the living cells of all plants and animals. The basic number varies in different species, though all contain the inherited blueprints that determine biological functions and features. At the chemical level, this miracle of heredity is performed by long spiral molecules of DNA. If the DNA threads in a single human gene are unwound, they measure about three feet.