DNA- Deoxyribonucleic Acid, Compostion, Characterstics-
DNA- Deoxyribonucleic Acid
- Deoxyribonucleic acid (DNA) is a molecule composed of two chains (made of nucleotides) which coil around each other to form a double helix carrying the genetic instructions used in the growth, development, functioning and reproduction of all known living organisms and many viruses. DNA and ribonucleic acid (RNA) are nucleic acids; alongside proteins, lipids and complex carbohydrates (polysaccharides), nucleic acids are one of the four major types of macromolecules that are essential for all known forms of life.
- DNA is appropriate for natural data stockpiling, since the DNA spine isimpervious to cleavage and the twofold abandoned structure furnishes the particle with an underlyingcopy of the encoded data. This data is repeated as when the two strandsindependent. An enormous piece of DNA (over 98% for people) is non-coding, implying that thesesegments don't act as examples for protein successions.
Components of DNA-
- There are three components, a pentose sugar, phosphoric acid and nitrogenous bases which combine to form monomer unit called as nucleotide. Large number of nucleotides joins to form polynucleotide chain. Each nucleotide is composed of one of four nitrogen-containing nucleobases i.e., cytosine (C), guanine (G), adenine (A) or thymine (T), a sugar called deoxyribose, and a phosphate group. The nucleotides are joined to one another in a chain by covalent bonds between the sugar of one nucleotide and the phosphate of the next, resulting in an alternating sugar-phosphate backbone. The nitrogenous bases of the two separate polynucleotide strands are bound together, according to base pairing rules (A with T and C with G), with hydrogen bonds to make double-stranded DNA.
The three components of DNA are:
(1) Sugar-
- The sugar present in DNA is a pentose sugarcalled as deoxyribose sugar. Its name indicates that it is derived from ribose sugar by loss of an oxygen atom. Deoxyribose sugar joins with a nitrogenous base to form nucleoside.
Structure of sugar
(2) Phosphoric acid-
- Phosphoric acid along with sugar molecule forms the backbone of polynucleotide chain. The bond formed by a phosphate between the sugar molecules of two different nucleotides is called phosphodiester bond. In one strand of DNA helix the phosphodiester bond is formed in the direction 3ˈ-5ˈ direction and in the other strand of the helix phosphodiester bonds are formed in 5ˈ-3ˈ direction.
(3) Nitrogenous bases-
- There are four nitrogenous bases present in structure of DNA which are grouped into two classes called as purines and pyrimidines. The complementary nitrogenous bases are divided into two groups, pyrimidines and purines. In DNA, the pyrimidines are thymine and cytosine; the purines are adenine and guanine.
Pyrimidines-
- Pyrimidines are simple aromatic compounds composed of carbon and nitrogen atoms in a six membered, heterocyclic ring system. The name also refers to a specific compound (composition C4H4N2), not found in nature that can be regarded as the parental structure of a wide range of naturally occurring chemical species. The most abundant naturally occurring pyrimidines are uracil (2, 4-dihydroxypyrimidine), cytosine (2-hydroxy-4-aminopyrimidine), and thymine (2, 4-dihydroxy-5-methyl pyrimidine). The first two are found predominantly in RNA, while the latter two are found predominantly in DNA. Small amounts of thymine are found in transfer RNA.
Structure of pyrimidine
- The two pyrimidines found in DNA are generally base-matched with a purine buildup on thereciprocal strand, so the purine to pyrimidine proportion in DNA is solidarity. In RNA, which is single-abandoned, this proportion shifts broadly.The term pyrimidine is likewise used to allude to pyrimidine subsidiaries, generally quite the threenitrogenous bases that, alongside the two purines, are the structure blocks of bothdeoxyribonucleic acids (DNA) and ribonucleic corrosive (RNA). The pyrimidine nitrogenous basesare gotten from the natural compound pyrimidine through the expansion of different usefulgatherings. Every pyrimidine ring has 2 nitrogen iotas present from the get go and third position and 4 carbon molecules present at second, fourth, fifth and sixth place of pyrimidine ring. In every one of the three pyrimidines C-2 isconnected to oxygen by double bond.
Purines-
- A purine is a heterocyclic aromatic organic compound that consists of a pyrimidine ring fused to an imidazole ring. Purine gives its name to the wider class of molecules, purines, which iclude substituted purines and their tautomers, are the most widely occurring nitrogen-containing heterocycle in nature. Purine is water soluble, are found in high concentration in meat and meat products, especially internal organs such as liver and kidney.
- All purines contain a twofold ringed construction that comprises of a six-membered ring combinedto a five-membered ring; consider a honeycomb cell joined to a pentagon. The purine ring isconsidered a heterocyclic particle, meaning it is a shut ring containing no less than two distinctsorts of particles. Every one of purines rings contains two nitrogen particles, for a sum of four inside thetwofold ringed design. These nitrogen molecules are situated in similar situations in all purines.
Structure of purine
- The leftover five situations inside the rings are involved via carbon particles. The purine ring iscircled by hydrogen molecules, which can be supplanted by different particles or gatherings of iotas to framevarious purines.
- Purines are twofold ringed nitrogenous bases viewed as present in nucleic acids. Both DNA andRNA contain two kinds of purines which are adenine and guanine. Carbon particles in purine ringare numbered in enemy of clock wise course and carbon molecules in imidazole ring are numbered inclockwise course. C-4 and C-5 are normal to both the rings. The four nitrogen iotas arepresent at first, third, seventh and ninth position.
Nucleoside-
- Nucleoside is a particle shaped by relationship of nitrogenous base and pentose sugar.Nitrogenous bases get joined to C-1 of pentose sugar. When a glycosidic bond is shapedamong sugar and nitrogenous base, C-1 of sugar is constantly involved. On the off chance that the nitrogenous base is apurine, the nitrogenous base is connected to the sugar by means of its N-9 particle, while on the off chance that it's a pyrimidine, it isconnected by means of its N-1 particle. Contingent on the kind of sugar present, nucleosides are of two types-
- Ribonucleosides and Deoxyribonucleosides. Because the pentose sugar present in DNA is deoxyribose, hence, nucleoside present in DNA called Deoxyribonucleosides.
There are four types of deoxyribose nucleosides present in DNA molecule:
1. Deoxyadenosine = Adenine + Deoxyribose
2. Deoxyguanosine = Guanine + Deoxyribose
3. Deoxycytidine = Cytosine + Deoxyribose
4. Deoxythymidine = Thymine + Deoxyribose
Nucleotide-
- Nucleotides are monomers which get connected to each other to frame a polynucleotide chainpresent in DNA atom. Nucleotides are the structure blocks of nucleic acids; they aremade out of three subunit particles: a nitrogenous base, a five-carbon sugar (ribose ordeoxyribose), and something like one phosphate bunch. Nucleotide is framed by expansion of phosphoriccorrosive to nucleoside. Thus one might say that a nucleotide is nucleoside monophosphate.
- The phosphate bunch gets appended to C-5 of deoxyribose sugar. Since there are foursorts of nitrogenous bases, subsequently, there exist four kinds of nucleotides which are:
- Deoxyadenosine monophosphate (dAMP), Deoxyguanosine monophosphate (dGMP), Deoxycytidine monophosphate (dCMP) and Deoxythymidine monophosphate (dTMP)
1. Deoxyadenylic acid or (dAMP) = Adenine + Deoxyribose + Phosphoric acid
2. Deoxyguanylic acid or (dGMP) = Guanine + Deoxyribose + Phosphoric acid
3. Deoxycytidylic acid or (dCMP) = Cytosine + Deoxyribose + Phosphoric acid
4. Deoxythymidylic acid or (dTMP) = Thymine + Deoxyribose + Phosphoric acid
