1. Molecular biology as a discipline in Biology has grown enormously in the last 50 years. In the beginning, molecular biologists wanted to understand the structure of biological molecules (proteins and DNA for example). More recently they have focused on a variety of issues about those molecules. Most importantly, they wanted to understand how genetic information in the form of the nucleic acid DNA is expressed in a useful form in cells.
2. In the 1950s it became clear that DNA contained the information necessary for construction of proteins. Early in the 1960s molecular biologists found evidence of an unstable form of nucleic acid, ribonucleic acid or RNA, that had the properties of a messenger. Messenger RNA (mRNA) is an exact copy of a short section of the DNA and carries that information to where proteins are being constructed. In a eukaryote DNA resides in the nucleus and proteins are constructed in the cytoplasm, so mRNAs must travel out of the nucleus into the cytoplasm.
3. The central organizing principle of molecular biology, called with tongue somewhat in cheek the "Central Dogma", is that DNA is expressed into RNA which is expressed into protein. More succinctly: DNA®RNA®protein.
4. The sequence of monomers in a DNA polymer (nucleotides) must first be copied into an exact replica in RNA. Using the analogy of a scribe copying out ("transcribing") a manuscript, this process is termed transcription. Then the mRNA must be converted from the "language" of nucleic acids (nucleotides) into the language of proteins (which are polymers of amino acids). Synthesis of proteins following mRNA instructions is called translation.
5. The one-to-one translation of proteins from mRNA relies on a code, the "genetic code", in which a group of three adjacent nucleotides (a "codon") specifies one of the 20 amino acids found in proteins. In the process of translation each successive codon in an mRNA is decoded into an amino acid, with the amino acids being joined together into a protein polymer. The protein product, when finished and released, folds spontaneously into a structure that allows it to perform its cellular function.

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1. The "Central Dogma" expresses how the information in DNA becomes converted into proteins.
2. DNA copied into an exact replica as an mRNA in a process called "transcription"
3. The process of converting an mRNA sequence into a protein is called translation