The DNA Molecule: Blueprint of Life

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  • Topic: DNA, Gene, RNA
  • Pages : 3 (848 words )
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  • Published : May 7, 2013
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The DNA molecule is often referred to as “The Blueprint of life”. Discuss. [SEP, 1999]

Synopsis
DNA structure
Why is DNA called “blueprint”
Features of the genetic code
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Deoxyribonucleic acid (DNA) is a vital component of both eukaryotic and prokaryotic cells. A blueprint is a detailed drawing or map which identifies and directs the construction and development of a building or an object. DNA is the hereditary material in almost all organisms. Nearly every cell in an organism’s body has the same DNA. DNA is the blueprint that guides the construction and development of living organisms. Some viruses have RNA as their genetic code.

DNA structure
DNA is a polymer, made up of many monomers called nucleotides which link together by condensation reactions. A nucleotide is composed of a pentose sugar called deoxyribose, a phosphate group and a nitrogenous base. Nucleotides link together by a phosphodiester bond.

Four types of bases occur in DNA. Two of the bases are purines - adenine and guanine.  The pyrimidines are thymine and cytosine. The pyrimidines are single ringed and the purines are double ringed.

DNA is composed of two antiparallel strands which are wound round each other in a right handed manner to form a double helix. In each strand the sugar and phosphate alternate to form a backbone and the bases are linked to the sugar. The two strands are held together by hydrogen bonds that occur between the bases. The way that bases link together is called complementary base pairing, where adenine always pairs up with thymine and guanine with cytosine. The base pairing is called complementary because there are specific geometry requirements in the formation of hydrogen bonds between the bases. This way of pairing, ensures that the bases fit in the space between the two strands. Two hydrogen bonds form between adenine and thymine and three between cytosine and...
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