The ABCs of molecular genetics

0 Comments | Saturday Evening Post, May-June, 2008

Dear Dr. SerVaas,

I consider myself an educated reader, but I have forgotten the basics about genes and how RNA differs from DNA, Could you address this in basic language?

Donald Ray

Indianapolis, Indiana

Molecular biologists explain it this way: DNA makes RNA, RNA makes protein, and proteins make us.

Our cells contain a unique set of 46 chromosomes, half from each parent. Chromosomes are long, coiled molecules of DNA (deoxyribonucleic acid) that together contain the blueprint for building cells on thousands of genes. In general, genes govern inherited traits and the synthesis, or manufacture, of proteins that regulate cell activity.

Remember, DNA makes RNA (ribonucleic acid), and RNA makes proteins. Only DNA passes genetic information from generation to generation. When the body needs certain proteins, DNA temporarily uncoils and separates at specific points. RNA molecules copy the gene sequence, then use it to produce proteins that control how our bodies look and function (see box above).

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For those interested in more technical terminology, the process of transmitting the genetic code from DNA to RNA is called transcription. The RNA molecule is usually a single strand that folds into different shapes and consists of base units (adenine, guanine, cytosine, and uracil) bonded together with the sugar ribose. DNA is a double, twisted strand containing thymine as a base unit instead of uracil. Inside of cells are three major types of RNA: transfer RNA to decode DNA, messenger RNA that is a temporary copy of genes, and ribosomal RNA to trigger protein synthesis. Researchers believe that additional types of RNA may be identified in the future.

Other common terms related to genetics include genome (all the genes in an organism's DNA), proteomics (the study of all the proteins controlled by a genome), and oncogene (a gene associated with cancer that often affects cell growth).

The Many Roles of Proteins

Proteins are needed for development and growth as well as for carrying out vital chemical functions in the body. Some proteins form structures such as hair and muscle. Others serve as antibodies, hormones, or enzymes, or (like oxygen-carrying hemoglobin) transport substances in the body.

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