The hereditary molecule that is tasked with carrying genetic instructions that are used in all living things in development, growth, reproduction and functioning is referred to as deoxyribonucleic acid (DNA). DNA molecules consist of two strands which are bipolar and are mostly coiled near to one another to form a spiral. This strands are referred to as polynucleotides simply because they are made of small units known as nucleotides.
The information of the DNA is stored in this nucleotides. This nucleotides are made of guanine, thymine, cytosine and adenine which are chemical bases, and they are usually denoted with letters G, T, C, and A respectively. In addition to the four chemical bases, the nucleotide has a sugar and a phosphate group. According to the base pairing rules, the two separate polynucleotides are bound together (A pairs T and C pairs G).
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How it works
Biological information is stored in DNA” its backbone is resistant to cleavage. The two strands store the same biological message, if the strands happen to separate the information in the strands is replicated. The double strands of DNA run in the opposite direction of one another.
Hence they are not parallel. In every sugar, one of the nucleobases types (A, T, G, and C) is attached. The sequence of this nucleobases, which is embedded in the backbone of the DNA, encrypts the biological information. Ribonucleic acid (RNA) is usually created by DNA strands in a process referred to as transcription, and the DNA strands act as the templates for this process.
Through the process of translation, the RNA strands using the genetic code create the amino acid within proteins sequence. (Glover, David, et al, 178)Chromosomes are structures into which DNA has been incorporated. During cell division, through the process DNA replication the chromosomes are duplicated, hence every cell is provided with chromosomes that are a complete set. Eukaryotic organisms which include fungi, animals and plants, use their cell nucleus is used to store most of their DNA and some of the DNA in organelles for example chloroplasts and mitochondria.
Whereas in bacteria and archaea (prokaryotes) use the cytoplasm to store their DNA. Histones are an example of proteins that structure and mold the DNA in eukaryotic chromosomes, this helps in controlling the parts that can be transcribed of the DNA, hence making the DNA and other proteins to interact smoothly.Classification of nucleobasesThe nucleobases in a DNA strand have to major groups. We have the purines, they include adenine denoted by (A) and guanine denoted by (G). The cytosine(C) and thymine (T) make up another group called pyrimidines.
Uracil is a pyrimidine nucleobase that RNA takes the place of thymine, the lack of methyl group on its ring, it makes it different from thymine.The DNA PropertiesNucleotides are units that make DNA and are repetitive hence causing a long polymer. Its dynamic along its length, hence making it possible to coil into loops and various shapes too. DNA in all species is comprised of paired chains that are brought together by hydrogen bonds. These chains join together around the same axis. It exists as molecules held tightly together in pairs rather than as a single molecule.
The strands interlace to form a double helix. Nucleotides are made of segments and nucleobase, the backbone is used to hold the chain together, and the nucleobase is used interact with another strand in the DNA in the double helix. A sugar that is linked to nucleobase is referred to as a nucleoside. And if a sugar that is combined with one or more phosphate groups is linked to a nucleobase then we have a nucleotide. While a polymer composed of multiple connected nucleotides is referred to as a polynucleotide. Alternating residuals of nucleotides and sugar make up the backbone of the strand of the DNA.
The sugar is a two deoxyribose that is a pentose sugar, phosphate groups join these sugars hence forming phosphodiester bonds. With these asymmetric bonds, it means that the DNA has a strand direction. The DNA strand is made stable by two units that is hydrogen bonds, which are used to bond nucleotides, the other is base stacking that is used for the nucleobases. The bases that are found in the DNA strand include ” Adenine, cytosine, guanine, and thymine, if these bases attached to a sugar-phosphate create a nucleotide. (Silverstein, Virginia, Laura, 269)
- Base pairingComplementary base pairing is where in a DNA double helix every nucleobase type from one strand links with only one type of nucleobase type from the other strand of. For instance, hydrogen bonds between purines and pyrimidines. Here adenine bonds to thymine with two hydrogen bonds, while cytosine to the guanine is bonded with three hydrogen bonds. This is a Watson-crick base pair, whereby two nucleotides across a double helix bound. In the case that there are two hydrogen bonds between guanine and cytosine then this is refed to as Hoostegeen base pairing.
- Sense and anti-sense Sense is the sequence of DNA, in case that the sequence of the messenger RNA is same as that of DNA, it is translated into a protein. An anti-sense is a sequence on the opposite strand, and these both can exist in the same double helix of DNA.
- Super-coilingDNA in its normal state forms a double helix that rotates once in every of its if base pairs, but if it’s twisted it becomes tight or loose. If turned towards the direction the helix is said to be positively super-coiled hence the bases are held more tightly, and if bent to the opposite direction it is supposed to be negatively super-coiled and the bases become loose and can disjoin easily.
- Alternative DNA structuresThere are different forms that DNA takes namely A, B, Z. These forms that the DNA take have been attributed to the super-coiling direction of the strands, the chemical modifications of the bases of the DNA, the level of hydration, existence of polyamines concentration and type of metal ions.
- Quadruplex structuresTelomeres are regions at the end of linear chromosomes. It uses the enzyme telomerase to allow the cell to replicate the ends of a chromosome. They also protect the ends of DNA and prevents the repair system of DNA form treating a cell as damage to be corrected.
- Branched DNAIn the event of existence of non-complimentary regions at the end of a strand that has a complementary region causes fraying of the DNA. A branched DNA can also survive if another strand of DNA comprises of intersecting regions is able to hybridize with the areas of preceding double-stranded that are frayed. DNA packaging and base modificationsHow a DNA is packaged in chromosomes, influences its expression of genes in a structure called chromatin, high levels of methylation of cytosine is directly linked with regions of low or no gene concentration.
(Dacascos, Jurgen, William, 297)DamageMutagens cause damage to DNA” these mutagens are ” oxidizing agents, alkylating agents and high electromagnetic radiations. Every mutagen creates a different type of DNA damage, for instance, electromagnetic radiation produces thymine dimers that form cross-links between pyrimidine, oxidants like hydrogen peroxide cause damages including base modifications, mostly of guanosine and breaks of double strands.
Glover, David M, David Dugan, Jeff Goldblum, James D. Watson, Francis Crick, Maurice Wilkins, and Peter Pauling. Dna. The secret of life, Princeton, NJ: Films for the Humanities & Sciences, 2008.
Silverstein, Alvin, Virginia B. Silverstein, and Laura S. Nunn.? Dna. Minneapolis: Twenty-First Century Books, 2009.
Dacascos, Mark, Jurgen Prochnow, and William Mesa.? Dna. La Crosse, WI: Platinum Disc Corporation, 2005.