DNA Diagram

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DNA is the basic hereditary material of organisms .It is seen in the cytoplasm as nucleoid and plasmids in prokaryotes and located inside the nucleus in eukaryotes.

DNA is the hereditary material through which characters are transferred from one generation to the next generation. It acts as the blue prints for the cell. The sudden change happening to the DNA is called mutation which results in alterations in the behavior of the cell.

Watson, Crick and Wilkins described the molecular arrangement of DNA .They were awarded the Nobel Prize in Medicine in 1962 for the discovery.

The proposed double helix model of DNA resembles a spiral ladder. It is made up of two polynucleotide chains paired by their nitrogen-containing bases. Two strands of alternating phosphate groups and deoxyribose sugars form the rail of the ladder.

Paired bases, held together by hydrogen bonds, form the steps of the ladder.

The nitrogenous bases are of two types-Purines and pyramidines.The two purines are Adenine and Guanine and the two pyrimidine are Cytosine and Thymine. One purine always pairs with one pyrimidine. Adenine always pairs with thymine and vice versa, and cytosine always pairs with guanine. The adenine and thymine pairs by two hydrogen bonds, cytosine and guanine pairs by means of three hydrogen bonds. The sugar and phosphate units in the DNA helix therefore build up the phosphate backbone of DNA.

It is in a specific way the twisted molecules are arranged, one strand is arranged in the 5' to 3' direction while the complementary strand is arranged in the 3' to 5' direction. The two strands are antiparallel to one another.

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