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The Dogma of Life

Cells are the fundamental working units of every living system. All the instructions needed to direct their activities are contained within the chemical DNA (deoxyribonucleic acid). Dogmas are authoritative tenets common in religion and philosophy. But in molecular biology? Molecular biology has a central dogma, proposed by Francis Crick in 1953, that says that genetic information flows from DNA to RNA to proteins.

The journey from raw genetic information to life begins inside the cell's nucleus. There, instructions for life are coded in the language of DNA, or deoxyribonucleic acid. DNA language is written with just four 'letters' (bases): A (for adenine), T (thymine), C (cytosine), and G (guanine). The 'D' in DNA comes from one of DNA's components, the sugar deoxyribose. The sugar in RNA, or ribonucleic acid, is ribose, which has one more oxygen atom than deoxyribose. RNA uses the same letters as DNA, but instead of T it uses a U (for uracyl). Whereas DNA is double stranded (it is composed of two backbones bonded by pairs of letters, A pairs with T and C pairs with G), RNA is single stranded.

RNA polymerases synthesize one type of RNA, messenger RNA (mRNA), which is a copy of the DNA sequence in the nucleus. Then, mRNA carries the genetic information from the nucleus to the protein-making machine of the cell, the ribosome. The ribosome reads the sequence of letters in the mRNA - every 3 bases code for an amino acid - to form proteins. Proteins are long chains of amino acids that make up muscles and hair, sense light, and regulate vital functions in the human body. One could say then that life is what it is, thanks to a dogma.


About the Author

Diego PinedaDiego Pineda
Diego holds a master's degree in science and technology journalism from Texas A&M University and work as a science writer for Immunizations for the Public Health (I4PH), a Texas-based nonprofit corporation that provides information services on vaccines and immunizations. He enjoys writing about genetics, bioethics, and physics -- both in English or Spanish.
Diego Pineda - Science Writer

Further Reading
The Double Helix: A Personal Account of the Discovery of the Structure of DNA
by James D. Watson, Lawrence Bragg

Related Web Links
RNA is an Intermediary between DNA and Protein
by Dolan DNA Learning Center

Bringing RNA Into View
by University of Utah

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