What is DNA?
Introduction:
Relative to the cell, the large nucleoprotein molecule is called deoxyribonucleic acid or DNA."DNA is the self-replicating, mutable, regulator of all biological functions and the carrier and carrier of hereditary characteristics contained in living cells." Chromosomes in the cell nucleus contain mainly DNA. However, some DNA is found in mitochondria, centrosomes, and even in the cytoplasm.
Discovery: In 1868, Miescher first discovered DNA.
The physical structure of DNA: DNA molecules in real cells are straight and unbranched like threads. They can be spherical in the original cells. The shape of DNA varies from cell to cell. The diameter of mitochondria is about 5 microns. Virus DNA is several microns long.
Chemical Structure of DNA: DNA is a single long large chemical compound. The molecular weight of each DNA molecule is between 106 and 109. Its chemical structure is discussed below.
Each DNA molecule is made up of:
1. A pentose sugar with five carbons
2. Inorganic phosphates and
3. With nitrogen-containing bases.
Nitrogen bases are of two types:
Purine: Consists of adenine and guanine.
Pyrimidine: Consists of thymine and cytosine.
A molecule of deoxyribose sugar combines with a molecule of nitrogenous base to form a molecule of nucleoside. Again, one molecule of nucleoside is combined with one molecule of inorganic phosphate to form one molecule of nucleotide.
If two nucleotides contain the nitrogenous base adenine, it is called D-oxy adenosine monophosphate. If guanine is present, it is called D-oxyguanosine monophosphate. If cytosine is present it is called D-oxycytosine monophosphate and if thymine is present it is called D-oxythymidine monophosphate.
The above four D-oxy ribonucleotides are the molecular structure of the largest DNA molecule. They are joined by hydrogen bonds to form the DNA molecule.
Structure of DNA molecule:
One of the world's best and breakthrough discoveries is the structure proposal of DNA. In 1953, James D. Watson and Francis Crick proposed a DNA model based on X-ray diffraction patterns of Franklin and Wilkins through various experiments. This model of DNA is known as Watson and Crick's double helix model. They received the Nobel Prize in 1963 along with Wilkins for this model proposal.
In 1953, scientists Watson and Crick formulated the model of DNA molecule, which is briefly mentioned below:
1. The DNA molecule is a large molecule consisting of several thousand nucleotides that is several billion times larger than a hydrogen molecule. A molecule is made up of two polynucleotide sequences. It is called a paired coil.
2. Two polynucleotide strands twist to the right like an iron ladder to form a double helix.
3. The rungs of the ladder are formed by sequential attachment of deoxyribose sugar (S) and phosphate (P) and the rungs are composed of two nitrogenous bases (A, C, T, G).
4. Of the two formulas one is upward, one is downward. That is, if the phosphate is attached to the 5th carbon molecule of the sugar of one nucleotide, the phosphate is attached to the 3rd carbon molecule of the sugar of the other nucleotide. The nitrogenous base is always attached to the 1st carbon of the sugar.
5. Bases are joined by hydrogen bonds. So the outside of the ladder is the phosphate and the inside is the nitrogenous base. Guanine of one formula is connected to cytosine of other formula by three hydrogen bonds (G≡C) and adenine of one formula is connected to thymine of other formula by two hydrogen bonds (A = T).
6. Two stair-like spirals revolve around an imaginary central axis. The two sutras are parallel but opposite to each other. That is, one formula is 5 to 3 oriented and the other is 3 to 5 carbon oriented.
7. Diameter of helix is 20Ã…. Length may vary.
8. 10 nucleotides are required to complete a patch.
9. A complete patch is completed every 34Ã… distance. Each patch contains about 25 hydrogen bonds.
10. The base pairs are 3.4Ã… apart at an angle of 36°.
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