DNA is the chemical name for the molecule that carries genetic instructions in all living things. The DNA molecule consists of two strands that wind around one another to form a shape known as a double helix. Each strand has a backbone made of alternating sugar (deoxyribose) and phosphate groups. Attached to each sugar is one of four bases--adenine (A), cytosine (C), guanine (G), and thymine (T). The two strands are held together by bonds between the bases; adenine bonds with thymine, and cytosine bonds with guanine. The sequence of the bases along the backbones serves as instructions for assembling protein and RNA molecules. DNA was first observed by a German biochemist named Frederich Miescher in 1869. But for many years, researchers did not realize the importance of this molecule. It was not until 1953 that James Watson, Francis Crick, Maurice Wilkins and Rosalind Franklin figured out the structure of DNA — a double helix — which they realized could carry biological information. Watson, Crick and Wilkins were awarded the Nobel Prize in Medicine in 1962 "for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material." Franklin was not included in the award, although her work was integral to the research. STRUCTURE OF DNA The discovery of the double helix structure of DNA was made thanks to a number of scientists in the 1950s. DNA structure can be thought of like a twisted ladder. This structure is described as a double-helix, as illustrated in the figure above. It is a nucleic acid, and all nucleic acids are made up of nucleotides. The DNA molecule is composed of units called nucleotides, and each nucleotide is composed of three different components, such as sugar, phosphate groups, and nitrogen bases. The basic building blocks of DNA are nucleotides, which are composed of a sugar group, a phosphate group, and a nitrogen base. The sugar and phosphate groups link the nucleotides together to form each strand of DNA. Adenine (A), Thymine (T), Guanine (G) and Cytosine (C) are four types of nitrogen bases. These 4 Nitrogenous bases pair together in the following way: A with T, and C with G. These base pairs are essential for the DNA’s double helix structure, which resembles a twisted ladder. Discovery of DNA The discovery of the double helix structure of DNA was made thanks to a number of scientists in the 1950s. DNA double helix, illustrating its right-handed structure. The major groove is a wider gap that spirals up the length of the molecule, while the minor groove is a smaller gap that runs in parallel to the major groove. The base pairs are found in the center of the helix, while the sugar-phosphate backbones run along the outside. DNA molecules have an antiparallel structure - that is, the two strands of the helix run in opposite directions of one another. Each strand has a 5' end and a 3' end. Solving the structure of DNA was one of the great scientific achievements of the century. Knowing the structure of DNA unlocked the door to understanding many aspects of DNA's function, such as how it is copied and how the information it carries can be used to produce proteins. What DNA is present in humans? There are two types of DNA in the cell – autosomal DNA and mitochondrial DNA. Autosomal DNA (also called nuclear DNA) is packaged into 22 paired chromosomes. In each pair of autosomes, one was inherited from the mother and one was inherited from the father. F DNA is the information molecule. It stores instructions for making other large molecules, called proteins. These instructions are stored inside each of your cells, distributed among 46 long structures called chromosomes. These chromosomes are made up of thousands of shorter segments of DNA, called genes. How much DNA is in the human body? The diploid human genome is thus composed of 46 DNA molecules of 24 distinct types. Because human chromosomes exist in pairs that are almost identical, only 3 billion nucleotide pairs (the haploid genome) need to be sequenced to gain complete information concerning a representative human genome.
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Allison Grey
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Gene Technology