03/10/97 DNA FOR DUMMIES: THE BASICS YOU NEED TO KNOW

"DNA FOR DUMMIES: THE BASICS YOU NEED TO KNOW

The blueprint of life is DNA. Its famous double helix is a long, long chain built by linking together four simple molecules. The order in which those molecules are linked determines the information contained in the DNA. It is the SEQUENCE of those molecules that molecular biologists are now busily decoding. All of the DNA in an organism is referred to as the organism's GENOME.

GENES are DNA chains made up of hundreds or thousands of simple molecules. Each gene contains instructions to make another type of crucial molecule, a PROTEIN. Proteins include everything from hormones such as insulin--which regulates blood-sugar levels--to enzymes that help digest the food we eat. Some proteins turn other genes on and off, which then affect still other genes, creating complicated feedback loops.
Individual proteins are but tiny cogs in incredibly complex biological systems. Consider the immune system, in which thousands of genes and proteins work together to field an army of cells and antibodies (another type of protein) against intruders. The DNA in each of the body's cells contains all the genetic information to produce a person. But in any given cell, only some of the genes are switched on; the rest are dormant. That's what makes a liver cell, say, different from a skin cell--different sets of genes are turned on in each."