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Introduction
DNA, or deoxyribonucleic acid, is more than simply a collection of nucleotides that have been meticulously organised and coordinated to form the notorious ‘double helix.’ DNA and its structure, which are commonly researched at a molecular level, have proven crucial in understanding evolution. The significance of DNA cannot be emphasised, as it has several uses in a variety of industries. Understanding and appreciating the structure and function of DNA have opened up many new research avenues, including genetic engineering, which is becoming increasingly popular. DNA fingerprinting and sequencing are also used extensively in forensic science and genealogy to get information.
What is DNA?
DNA is a molecule in charge of carrying and transferring genetic information or blueprints from parents to children. Deoxyribonucleic acid is the correct term for DNA. It’s a molecularly distinct organic chemical with a distinct molecular structure. It can be present in prokaryotic and eukaryotic cells alike.
Besides being responsible for transmitting genetic data in all living things, DNA is also essential for protein synthesis. Nuclear DNA seems to be the DNA found in every cell of a eukaryotic organism’s nucleus. It is responsible for the bulk of the organism’s genomes, with mitochondrial and plastid DNA handling the rest.
Mitochondrial DNA refers to the DNA found in the cell’s mitochondria. There are around 16,000 base pairs in mitochondrial DNA in humans. Plastids, too, get their DNA & play an essential part in photosynthesis.
Types of DNA
There are three distinct forms of DNA:
DNA in the B-form:
Most people are familiar with B-DNA, which is the Watson–Crick version of the double helix. Two strands of DNA, each in a right helix, would be twisted around the same axis, they proposed. H-bonding between the bases holds the two strands together. The duplex’s two strands are platonically coiled and antiparallel. The nucleotides on one strand that are arranged in a 5′ to 3′ orientation match with corresponding nucleotides on the opposing strand that are arranged in a 3′ to 5′ orientation.
DNA in its A-form:
The confirmation of the deoxyribose sugar ring is the main distinction between A-form and B-form nucleic acid. In B-form, it is in the C2′ endocon formation, whereas in A-form, it is in the C3′ endocon formation. The placement of base-pairs within the duplex is a second major difference between A-form and B-form nucleic acids. The base pairs are almost centered over the helical axis in B-form, whereas they are pushed away from the central axis and closer to the main groove in A-form. In A-form, this results in a ribbon-like helix with a more open cylindrical core.
DNA in the Z-form:
Z-DNA has a drastically unusual duplex structure, with the two strands coiling in left-handed helices and the phosphodiester backbone having a prominent zig-zag pattern (hence the name). When DNA is in an alternating purine-pyrimidine sequence, such as GCGCGC, Z-DNA can develop because the G and C nucleotides are in different conformations, resulting in a zig-zag pattern. The G nucleotide is where the significant difference is.
Discovery
Friedrich Miescher, a Swiss researcher, discovered DNA in 1869 while researching the makeup of lymphoid cells (white blood cells). Instead, he extracted a novel molecule from a cell nucleus that he named nucleon (DNA with related proteins).
Structure of the DNA
The DNA molecule’s structure resembles a twisted ladder. Nucleotides are the building blocks of DNA, and every nucleotide is made up of three separate components: sugar, phosphate groups, and nitrogen bases. Each strand of DNA is formed by the sugar-phosphate groups linking the nucleotides together. Nitrogen bases include adenine (A), thymine (T), guanine (G), and cytosine (C).
The four nitrogenous bases are coupled in this sequence: A with T, C with G. The double helix structure of DNA resembles a twisted ladder that requires these base pairs. The genetic code, or DNA instructions, is determined by the arrangement of the nitrogenous bases. Sugar is the backbone of the DNA molecule, and it is one of the three components that make up its structure. It’s also known as deoxyribose. The opposing strands’ nitrogenous bases establish hydrogen bonds, generating a ladder-like structure.
Purines are A and G, whereas pyrimidines are C and T. DNA is split into two strands that run in opposing directions. The hydrogen connection between the two complementary bases holds these strands together. The strands become helically twisted, with each strand forming a right-handed spiral and a single turn consisting of 10 nucleotides. Each helix has a 3.4 nm pitch. As a result, 0.34 nm separates two successive base pairs. Chromosomes are composed of a single molecule of DNA that coils up to form chromosomes. In the nucleus of each cell, humans contain about twenty-three pairs of chromosomes. In the process of cell division, DNA is also essential.
DNA Characteristics
- Right-handed and left-handed DNA helices exist. The B – conformation of DNA with right-handed helices, on the other hand, is the most stable.
- The two strands of DNA split from one other when heated, then re-hybridize when cooled.
- Melting temperature is the temperature at which the two strands are entirely separate (Tm). The melting temperature varies depending on the sequence.
- Because the C-G pair contains three hydrogen bonds, the B sample of DNA with the higher melting point should have a greater C-G concentration.
- The amino acid sequence of every protein in all animals is encoded by the arrangement of bases along the DNA molecule.
Conclusion
DNA is a molecule in charge of carrying and transferring genetic information or blueprints from parents to children. Deoxyribonucleic acid is the correct term for DNA. There are three distinct forms of DNA, namely A-DNA, B-DNA, and Z-DNA.
The DNA molecule’s structure resembles a twisted ladder. Each strand of DNA is formed by the sugar-phosphate groups linking the nucleotides together. Adenine (A), thymine (T), guanine (G), & cytosine (C) are nitrogen bases (C). During cell division, the replication of DNA is a critical activity. Also, it’s known as semi-conservative duplication, which occurs when DNA duplicates itself. Apart from carrying genes, DNA has various processes.
