Genetics

About Dna Structure



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Deoxyribonucleic acid, DNA for short, is the hereditary material found in humans. DNA is located in the nucleus of almost every body cell and is considered to be the human blueprint. Structure wise, DNA is made up of nitrogen bases, hydrogen bonds, phosphate groups and the sugar, deoxyribose all wound together tightly.The four bases in DNA are Adenine, Guanine, Cytosine and Thymine. The phosphates and sugars (deoxyribose) form the backbone of the double helix while the bases act like the rungs on a ladder. The sequences that the bases are found in is what determines the instructions found in the DNA. The instructions  for  proteins which in turns represent a gene.

Each group of units in DNA is composed of a base attached to a phosphate and a sugar backbone. The sugar, one which contains five carbons, is deoxyribose. This is then attached to a phosphate group and a sugar, Cytosine, Guanine, Thymine or Adenine. Each of these units is connected to another unit both above and below it, as well as across from it. The unit which is across from it is attached by a corresponding base. If the original nitrogen base is guanine, the corresponding base would be cytosine. If the original base is adenine, the corresponding base is thymine.


When the two DNA strands that are corresponding are lined up they are wound together in a tight double helix. The two strands are held together by bonds, strong, yet weak enough to be able to be broken apart when DNA replication is to occur. These somewhat weak bonds are called hydrogen bonds. It is these hydrogen bonds which help with the stability of DNA. When Guanine and Cytosine are paired, they have three hydrogen bonds between them, making them a more stable pair than adenine and thymine, which share two hydrogen bonds.


DNA structure was discovered by scientist Watson and Crick who used X-Ray diffraction studies to show that the DNA molecule was in the shape of a double helix. When DNA is treated with various enzymes, it loses this double helix shape and can be broken apart into individual strands. This is necessary, when DNA replication is to occur, and new strands are produced. This procedure is necessary for the cell growth in an organism. An enzyme known as helicase splits the DNA molecule by unwinding it, leaving its two original strands open so that each can then get a complementary DNA strand with the help of another enzyme, one called DNA polymerase.

The structure and functions of DNA are very complex and are interdependent upon proteins. The presence of many important proteins, known as enzymes play a role in DNA structure and function. DNA contains a code or set of instructions within it to help regulate cell structure and function, and life itself.



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