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The bases of one helical strand in DNA are paired with complementary bases of the other. The configuration of the DNA molecule is highly stable, allowing it to act as a template for the replication of new DNA molecules, as well as for the production (transcription) of the related RNA (ribonucleic acid) molecule. A segment of DNA that codes for the cell's synthesis of a specific protein is called a gene.
DNA replicates by separating into two single strands, each of which serves as a template for a new strand.
The new strands are copied by the same principle of hydrogen-bond pairing between bases that exists in the double helix. Two new double-stranded molecules of DNA are produced, each containing one of the original strands and one new strand. This "semiconservative" replication is the key to the stable inheritance of genetic traits. Within a cell, DNA is organized into dense protein-DNA complexes called chromosomes. The genetic material of viruses may be single- or double-stranded DNA or RNA. Retroviruses carry their genetic material as single-stranded RNA and produce the enzyme reverse transcriptase, which can generate DNA from the RNA strand. Courtesy
Encyclopędia Britannica, Inc.
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