Nucleic acids are vital for cell functioning, and therefore for life. There are two types of nucleic acids, DNA and RNA. Together, they keep track of hereditary information in a cell so that the cell can maintain itself, grow, create offspring and perform any specialized functions it's meant to do. Nucleic acids thus control the information that makes every cell, and every organism, what it is.
Definition
Nucleic acids are a macromolecule found in cells. Like proteins and polysaccharides, the other macromolecules, nucleic acids are long molecules made up of many similar linked units.
There are two classes of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Each is made up of four different nucleotides--adenine, cytosine, guanine, and thymine in DNA, and adenine, cytosine, guanine and uracil in RNA.
DNA
DNA is a hereditary molecule that maintains and transmits information that cells need in order to survive and create offspring. It has two functions: to replicate itself during cell division, and to direct transcription (creation) of RNA. The information it contains is found in genes, which are sections along the DNA molecule that contain a "code" that the cell uses to create RNA and, ultimately, proteins. DNA is a double-stranded helix; this structure helps store information safely by essentially maintaining a double copy of its information.
RNA
RNA is created when the cell "reads" genes from DNA and makes a copy of them. RNA can also function as a hereditary molecule, storing information permanently the way DNA does, in viruses. In non-viral cells, messenger RNA (mRNA) copies information from DNA and brings it to the cell's machinery for creating proteins, the ribosomes. Ribosomes use the information in RNA as blueprints to create proteins, and proteins carry out nearly all of the cell's functions. Transfer RNA (tRNA) carries amino acids to the ribosomes in order to synthesize proteins.
Importance in Science
Nucleic acids are the only way a cell has to store information on its own processes and to transmit that information to its offspring. When nucleic acids were discovered to be the carriers of hereditary information, scientists were able to explain the mechanism for Darwin and Wallace's theory of evolution and Mendel's theory of genetics.
Importance in Disease
Understanding how genes are read by the cell and used to create proteins creates enormous opportunities for understanding disease. Genetic diseases occur when errors are introduced into the genes that DNA carries; those errors create faulty RNA, which creates faulty proteins that don't function the way they're supposed to. Cancer is caused by damage to DNA or interference with the mechanisms for its replication or repair. By understanding nucleic acids and their mechanics of action, we can understand how diseases occur and, eventually, cure them.
