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The sequence of nucleobases on a nucleic acid strand is translated by cell machinery into a sequence of amino acids making up a protein strand. Each group of three bases, called a codon , corresponds to a single amino acid, and there is a specific genetic code by which each possible combination of three bases corresponds to a specific amino acid.
Three sequences, UAG, UGA, and UAA, known as stop codons, [note 1] do not code for an amino acid but instead signal the release of the nascent polypeptide from the ribosome. [7] In the standard code, the sequence AUG—read as methionine—can serve as a start codon and, along with sequences such as an initiation factor, initiates translation.
Nucleic acids are formed when nucleotides come together through phosphodiester linkages between the 5' and 3' carbon atoms. [3] A nucleic acid sequence is the order of nucleotides within a DNA (GACT) or RNA (GACU) molecule that is determined by a series of letters.
DNA and ribonucleic acid (RNA) are nucleic acids. Alongside proteins, lipids and complex carbohydrates (polysaccharides), nucleic acids are one of the four major types of macromolecules that are essential for all known forms of life. The two DNA strands are known as polynucleotides as they are composed of simpler monomeric units called nucleotides.
Biomolecular structure is the intricate folded, three-dimensional shape that is formed by a molecule of protein, DNA, or RNA, and that is important to its function.The structure of these molecules may be considered at any of several length scales ranging from the level of individual atoms to the relationships among entire protein subunits.
From the very early stages of structural studies of DNA by X-ray diffraction and biochemical means, molecular models such as the Watson-Crick nucleic acid double helix model were successfully employed to solve the 'puzzle' of DNA structure, and also find how the latter relates to its key functions in living cells.
With some exceptions, [1] a three-nucleotide codon in a nucleic acid sequence specifies a single amino acid. The vast majority of genes are encoded with a single scheme (see the RNA codon table ). That scheme is often called the canonical or standard genetic code, or simply the genetic code, though variant codes (such as in mitochondria ) exist.
DNA sequencing is the process of determining the nucleic acid sequence – the order of nucleotides in DNA. It includes any method or technology that is used to determine the order of the four bases: adenine, guanine, cytosine, and thymine. The advent of rapid DNA sequencing methods has greatly accelerated biological and medical research and ...