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Nucleic acid and protein synthesis are connected through a series of steps that occur within biological cells. The genetic information of a living organism, which is encoded in its deoxyribonucleic acid (DNA), is expressed through the synthesis of proteins. The interactions of nucleic acid and protein synthesis can be broken down into two processes: transcription, in which the information in DNA is transcribed onto a ribonucleic acid (RNA) template, and translation, in which the RNA template is used to form a protein.
A molecule of DNA consists of two long chains of subunits called nucleotides, which are bonded to each other to form the characteristic double helix shape. Each nucleotide includes a molecular component known as a nucleobase, of which there are four types: adenine (A), guanine (G), cytosine (C), and thymine (T). In RNA, thymine is replaced by uracil (U). The organism’s genetic information is stored in repeating patterns of these four bases. Each nucleobase forms a base pair with a complementary nucleobase on the opposite strand — adenine binds with thymine or uracil, and guanine binds with cytosine.
During transcription, the first step in connecting nucleic acid and protein synthesis, enzymes split the DNA into its two constituent strands. A molecule of messenger RNA (mRNA) is then assembled from the exposed DNA template. MRNA is formed by enzymes which attach complementary nucleobases to those in the DNA, creating a copy of the information in a chain of nucleotides. This chain is then released from the DNA, forming a single-stranded mRNA molecule.
Transcription occurs in the nucleus of the cell, but the next step, translation, occurs in the cytoplasm — specifically, at the site of organelles known as ribosomes. MRNA moves to the ribosome and is decoded in sets of three-nucleotide codons. Each codon in mRNA corresponds to a complementary anticodon carried by a transfer RNA (tRNA) molecule. For example, the mRNA codon with bases GAU corresponds to the tRNA anticodon CUA.
Each tRNA molecule consists of the nucleotide triplet attached to a specific amino acid. As tRNAs bond to the mRNA strand, the amino acids they carry link together, forming a polypeptide chain. Eventually, translation is terminated and the polypeptide chain is completed, forming a protein.
Transcription and translation link nucleic acid and protein synthesis in multiple ways. The information in mRNA controls the sequence of amino acids in the polypeptide chain, and thus determines the protein being formed. MRNA is constructed from the original DNA sequence. TRNA, another nucleic acid, also plays an important role in constructing the polypeptide chain. In these ways, nucleic acid and protein synthesis are biological concepts which are intricately connected.