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What is DNA, What are the properties and functions of DNA?
What is DNA, What are the properties and functions of DNA?
DNA, or deoxyribo nucleic acid, is a nucleic acid that carries genetic instructions necessary for the biological development and viability functions of some viruses and all organisms. The main role of DNA is the long-term storage of information. DNA is likened to a template or pattern because it covers the information needed to build other components that belong to the cell, such as RNA and Protein. DNA fragments covering genetic information are called genes, but other DNA sequences also have structural functions (such as determining The Shape of chromosomes). Other DNA sequences help regulate the conditions under which genetic information will be used and in which cells.
DNA consists of two long polymers, chemically called nucleotides, consisting of simple units. The backbone of polymers, on the other hand, consists of phosphate-sugar groups connected by ester bonds. Each sugar group in phosphate and sugar, which extend in the opposite direction to each other, is connected to one of the four molecules. This sequence, created along the DNA backbone, encodes genetic information. When this encoded information is read through the genetic code throughout protein synthesis, they determine the amino acid sequence of proteins. Information in DNA is copied (transcribed) to RNA, another nucleic acid, during this process.
DNA is found in structures called chromosomes within cells. Before the cell divides, these chromosomes are mapped, and at this time, DNA dualization occurs. Eukaryotic organisms, such as fungi, animal protista and plants, have their DNA inside the cell nucleus. In prokaryotic creatures such as bacteria and Arche, DNA is located in the cytoplasm of cells. Like histones, chromatin proteins contained in chromosomes compress and organize DNA. These congested and complex structures that are mentioned regulate the interactions between proteins and DNA and control which parts of the DNA to read.
What Are The Properties Of DNA?
DNA, which is 2.2 to 2.6 nanometers wide, is 0.33 nanometers long. DNA polymers consist of millions of nucleotides, and each unit is very small. Half of the DNA comes from the male individual and the other half from the female individual. DNA consists of a pair of molecules tightly wrapped together, not as a single molecule in living things. These molecules wrap around each other like ivy and form a double helix. Phosphate and sugar form the backbone of the DNA molecule, while the base interacts with the other DNA strand in the double helix. A base bound to one or more phosphates and a sugar is called a nucleotide, and a base bound to only one sugar is called a nucleoside. The fact that more than one nucleotide is connected to each other is also called polynucleotide.
The sugar found in DNA is five-carbon sugar (pentose). The phosphate group, located between carbon 3 of one of the two adjacent sugars and carbon 5 of the other, binds the sugars together, forming a phosphodiester bond. Because this bond is asymmetric, there is one side of the DNA strand. The direction in which nucleotides in one strand bind to each other is the opposite of those in the other strand. This order, which exists in DNA strands, is called anti-parallel. Hydrogen bonds between the bases attached to the two strands stabilize the DNA. Four bases in DNA; it is called cytosine, adenine, thymine and guanine. The four bases mentioned bind to phosphate and sugar to form nucleotides. For example, adenosine monophosphate is a nucleotide. Bases classified as two types are purine derivatives such as guanine and adenine. These derivatives, formed by the fusion of 5-and 6-membered rings, are heterocyclic compounds. Thymine and cytosine are pyrimidine derivatives and consist of six-membered rings. Uracil, on the other hand, can rarely be involved in DNA as a result of the destruction of cytosine. For example, RNA that has similarities to DNA has uracil, not thymine.
What is DNA
Biological Functions Of DNA
DNA is circular in prokaryotes and linear chromosomes in eukaryotes. A set of chromosomes in a cell is called the genome of that cell. The human genome consists of about 3 billion base pairs located within chromosomes (46 chromosomes). Information encoding functional RNA molecules and proteins is found in the sequence of DNA fragments (genes). The transfer of this genetic information in genes occurs as a result of base matching. For example; copying a DNA sequence in the form of a complementary RNA sequence during transcription is possible by attraction between DNA and RNA nucleotides. During a protein cycle called translation, the protein corresponding to the RNA sequence is synthesized, at the same time, base matching occurs again between RNA nucleotides. Another important biological function is the process of copying genetic information in the cell, called DNA twinning.
Can DNA damage occur?
Some mutagens can cause DNA damage, resulting in changes in the DNA sequence mentioned above. Oxidizer, i.e. oxidative factors, electromagnetic rays with high energy and alkylating factors, mutagens can be given as examples. The type of damage that occurs in DNA depends on the type of mutagenesis. For example, ultraviolet light creates twos of thymine, damaging DNA. Despite this, amplifying factors such as hydrogen peroxide and free radicals can cause various types of damage. Two-strand breaks and base change can be shown as examples of these damages.
500 bases are damaged daily in a human cell. The most damaging of these damages is called double-chain breakage. This damage is very difficult to repair and can cause insertions, point mutations, deletions in DNA. Many mutagens enter the space between two base pairs, this condition is called intercalation. Many of the intercalators are planar and aromatic molecules (such as bromide, ethidium, doxorubicin, and daunomycin). In order for any intercalator to enter between the base pair, the gap between the base pairs must be opened, and in order for this to happen, the DNA helix must be loosened in the opposite direction. If these occur, DNA and transcription duality is prevented, mutations and poisoning occur. Because of this, DNA intercalators are usually carcinogenic, and the best-known examples are acridine, benzopyrene, ethidium bromide, and aflatoxin, derivatives of diol epoxide. Despite all this, due to their ability to interfere with DNA transcription, these toxins are used in chemotherapy to prevent rapidly developing cancer cells.
All modern living things can function, that is, reproduce and grow with the genetic information contained in DNA. Despite this, from the beginning of humanity to date, DNA has not been proven to perform this function, and it has been argued that the inherited material used in this sense is RNA. RNA may have played an important role in the metabolism of the first cells, both because it has a catalyst nature as part of ribozymes and because it transmits genetic information. In particular, this ancient RNA world, in which nucleic acids play a role in both catalysis and inheritance, may have influenced the evolution of the modern genetic code to consist of 4 nucleotide bases.
It has been assumed that a small number of bases in a living being will increase replication efficiency, while a large number of bases will increase the catalytic efficiency of ribozymes. As a matter of fact, there is no conclusive evidence about genetic systems in ancient times, because it is not possible to obtain DNA from many fossils. The reason for this is that the DNA affected by environmental conditions is broken into small pieces over time in the solution. There are also some claims that ancient DNA was isolated. In particular, it is argued that living bacteria were isolated in the salt crystal, which remained about 250 million years ago, but such claims are only conjecture.