Nucleotide
A nucleotide is a fundamental building block of nucleic acids, specifically deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), which are essential for storing and transmitting genetic information. Each nucleotide consists of three components: a sugar molecule (deoxyribose in DNA and ribose in RNA), a phosphate group, and a nitrogenous base. There are five types of nucleotides, which include the bases adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U) in RNA. In DNA, the bases pair specifically; adenine pairs with thymine, while cytosine pairs with guanine, forming a double helix structure that resembles a twisted ladder.
Nucleotides can be produced within the body (endogenous) or obtained from dietary sources (exogenous), making them crucial for cellular function and health. A deficiency in nucleotides can impede DNA and RNA functions, potentially leading to serious health issues. The study of nucleotides, including their origins and functions, continues to be an area of scientific research, particularly in understanding how life may have begun on Earth. This exploration includes experiments that simulate prehistoric conditions to observe the formation of nucleotides. Overall, nucleotides are vital for the cellular processes that govern growth, reproduction, and genetic inheritance across all living organisms.
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Nucleotide
A nucleotide is a component of deoxyribonucleic acid, or DNA, and ribonucleic acid, or RNA. These nucleotides store the genetic information that helps in the formation of genes. They also help in the formation of proteins necessary for cell development and health. Nucleotides are one of the elements extracted from food and sent to cells during the digestive process. As part of ongoing studies into the origin and function of nucleotides, scientists have determined that at least some nucleotides likely formed spontaneously as life was forming in prehistoric times.
Background
All living organisms contain DNA, which includes all the instructions given to cells for how to develop and operate. DNA determines what function a cell will have and directs the production and formation of that cell. Nucleotides play a crucial role in the creation of DNA.
Scientists knew that DNA existed for years before they were able to describe what it is made of or what it looks like. In the 1950s, English chemist Rosalind Franklin and Maurice Wilkins, a New Zealand–born British physicist, used x-rays to study DNA. Although they struggled with professional differences, the pair managed to capture x-ray images of DNA.
Two molecular biologists, American James Dewey Watson and Englishman Francis Crick used the x-rays to study the DNA molecule. They were able to determine that it is in a formation known as a double helix, resembling a ladder that had been twisted into a corkscrew shape. This led to the understanding of how DNA is formed and how it provides a blueprint for the formation and function of cells. For this discovery, Watson, Crick, and Wilkins received the Nobel Prize in Physiology or Medicine in 1962. Franklin, who died in 1958, was not immediately recognized for her contribution; her role was acknowledged later.
Overview
Every cell in a living organism contains biomolecules, or organic compounds that help determine what that cell will be and how well it will work. One type of these biomolecules is known as a nucleotide. There are five types of nucleotides that make up DNA and RNA. Nucleotides are made up of three components. They include a molecule of deoxyribose, or sugar, and a molecule of phosphoric acid, a phosphate. The third component in a nucleotide is a base.
DNA bases are one of four types of chemicals. They can be either adenine (A), cytosine (C), guanine (G), or thymine (T). Adenine and guanine are known as purines, while thymine and cytosine are pyrimidines. These four bases pair up in a specific formation. A and T pair together, as do C and G; each pair includes a purine and a pyrimidine. RNA is similar, except instead of thymine they include another purine called uracil. Each base attaches to a molecule of sugar and phosphate. In the twisted ladder-like double helix formation, the sugar and phosphate form the sides of the ladder and the bases provide the rungs. The way these molecules combine and pair together make it possible for DNA to replicate itself; this is how cells know how to reproduce and how traits are passed from parent to child.
The nucleotides can have one, two, or three phosphate groups attached. These combinations are called monophosphates, diphosphates, and triphosphates, respectively. It is also possible for a configuration to exist with no phosphate. When there is only a base and sugar molecule, they form a nucleoside instead of a nucleotide.
Bases combined with sugar molecules assume a different name. Adenine becomes adenosine, guanine becomes guanosine, and thymine becomes thymidine. Nucleotides are named with three-letter abbreviations that come from the name of the base/sugar combination and the type of phosphate that is connected to it. For instance, a nucleotide with adenosine (A) that is connected to a triphosphate (TP) would become ATP.
These nucleotides connect to each other between the sugar molecule on one nucleotide and the phosphate molecule of the second. This creates nucleic acid, which combines in various patterns to form DNA. The way that these combinations come together provides the instructions to cells; these formations are known as chromosomes. These chromosomes determine the characteristics of individual cells and cumulatively determine the overall structure and design of the larger organism.
Organisms get nucleotides in one of two ways. Some are produced by the body. These are known as endogenous nucleotides because they are produced within; the prefix endo- is from the Greek word for "within," "inner," or "containing." Other nucleotides are absorbed from food sources. These dietary nucleotides are called exogenous nucleotides because they come from outside the body; exo comes from the Greek word for "outside" or "out of." Since all these nucleotides are needed to form DNA, it is important for any living organism, including humans, to ingest varied food sources that provide all five types of nucleotides. Without sufficient quantities of nucleotides, neither DNA nor RNA can function properly. DNA will not be able to properly control the function of cells, and RNA will not be able to help cells form proteins. This can result in damage to the cells and the tissues those cells make up and create serious health problems.
Once an organism ingests these nucleotides, the digestive process helps to extract them from the food. In humans, this happens when the pancreas releases deoxyribonuclease to work on DNA and ribonuclease to work on RNA. This creates short segments of nucleotides that are suitable for use by the cells.
Scientists still have much to learn about DNA, RNA, and their components. One area of study includes determining the origin of the first nucleotides that led to life. Some researchers have been able to observe how this might have happened by combining bases and sugars in a model environment representing the conditions on prehistoric earth. Researchers from the Georgia Institute of Technology have observed the successful combination of bases known to have existed in the prebiotic, or pre-life, time of the earth.
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