Genes are made up of DNA, the famous double helix, and they reside on long, densely packed fibers called chromosomes. The rest is called junk DNA, because it has no apparent function. The information encoded in genes must be copied into RNA, a close cousin of DNA, and then used to assemble proteins, the real workhorses of the cell. Hemoglobin, which carries oxygen through the bloodstream, is one example.
Proteins have their own code, which is more complex than the genetic code.
Among the things the protein code does is knot the molecules into the complicated shapes necessary for them to function properly. A mistake in a single base in a gene that is thousands of bases long can lead to serious disease. Other illnesses, such as heart disease and obesity, are more complex, resulting from particular combinations of genes. Specific genes are flipped on at different times in different tissues. The McGraw-Hill Companies Inc. All rights reserved.