DNA

Article

January 23, 2022

DNA (DeoxyriboNucleic Acid, deoxyribonucleic acid, deoxyribonucleic acid) is a high molecular compound with a double helix structure in which two long strands, which are polymers of nucleotides, are twisted together. Although it was discovered in the nucleus of a cell and given the name nucleic acid, organelles other than the nucleus also have independent DNA, such as mitochondrial DNA. DNA consists of strands in which four types of nucleotides are connected through polymerization. This strand is often called a DNA sequence because cytosine, guanine, adenine, and thymine are distinguished by unique nucleobases. The DNA sequence can be divided into a gene section representing genetic information and an uncoding DNA section that does not. Even if it was a gene with a function in the past, when it becomes a pseudogene that loses its function through mutation, it becomes uncoding DNA. DNA replicates itself and causes gene expression through genetic information. A gene is a specific section of a DNA chain and includes exon sections that are involved in expression such as actual protein formation and introns that do not. DNA does not directly carry out gene expression, and the actual expression process is carried out by codons of messenger RNA (mRNA) transcribed from DNA. A codon is a genetic unit in which three base sequences are bound, and consists of a start codon, a stop codon, and codons that indicate the actual amino acid binding between them. mRNA makes ribosomes synthesize enzyme-like proteins. DNA was first discovered by Friedrich Mischer of Switzerland in 1869. He called it a nuclein, meaning an acid found in the nucleus of a cell. Since then, DNA has been pointed out as the cause of heredity for a long time. In 1944, through the transformation experiment of Oswald Avery, DNA was confirmed as the genetic material, and in 1952, it was confirmed by the Hershey-Chase experiment of Alfred Hershey and Martha Chase. The double helix structure of DNA was first revealed by James Watson and Francis Crick in a 1953 paper in the journal Nature. However, the X-ray diffraction image of DNA, which is conclusive evidence that DNA has a double helix structure, was taken by Rosalind Franklin, and Wilkins, a fellow scientist who was an ally of her, analyzed the diffraction images without Franklin's prior permission and provided them to Watson and Crick. Because Watson and Crick's research was possible, they were later criticized for "stealing Franklin's glory." Meanwhile, Franklin died of cancer in 1958 and was not nominated for the Nobel Prize.

Structure

DNA has a double helix structure in which two polymers of nucleotides are twisted together. Nucleotides constituting DNA are centered on deoxyribose, and phosphate is bonded to one side, and one of four types of nucleobases is bonded to the other side. The deoxyribose and phosphate groups form the backbone of a single chain through the polymerization process, and the nucleobases form base pairs through complementary hydrogen bonds to form a double helix. On the other hand, this complementarity of DNA means that only one side can predict the other. The double helix structure is essential for the functioning of DNA. The nucleobases of nucleotides store genetic information, and because they are held by hydrogen bonds, they can be easily released and closed. Because of this, the double helix can be partially unwound and closed for gene expression, or it can be fully unwound and replicated during cell division. The partially or completely unwrapped double helix is ​​closed again when gene expression is terminated or replication is complete. Meanwhile

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