Structure of Nucleic Acids

Structure of Nucleic Acids - Attached to the remaining free...

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Structure of Nucleic Acids The Deoxyribose Sugar The deoxyribose sugar in DNA is a pentose, a five-carbon sugar. Four carbons and an oxygen make up the five-membered ring; the other carbon branches off the ring. Similar to the numbering of the purine and pyrimidine rings (seen in ), the carbon constituents of the sugar ring are numbered 1'-4' (pronounced "one-prime carbon"), starting with the carbon to the right of the oxygen going clockwise (). The fifth carbon (5') branches from the 4' carbon. Figure %: Deoxyribose Sugar It is from this numbering system of the sugar group that DNA gets its polarity. The linkages between nucleotides occur between the 5' and 3' positions on the sugar group. One end has a free 5' end and the other has a free 3' end.
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Unformatted text preview: Attached to the remaining free carbons at the 1', 3' and 5' positions is an oxygen-containing hydroxyl group (-OH). The DNA sugar is called a de oxyribose because it is lacking a hydroxyl group at the 2' position. Instead there is just a hydrogen (see ). Phosphates A phosphate group consists of a central phosphorous surrounded by four oxygens. Figure %: Phosphate Group The phosphorous is single-bonded to three of the oxygens and double-bonded to the fourth. Due to the nature of the chemical bonds, there is a negative charge on each oxygen that has only one bond coming off of it. This negative charge accounts for the overall negative charge on the phosphate backbone of a DNA molecule....
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This note was uploaded on 01/27/2012 for the course BIOLOGY BSC1005 taught by Professor Rodriguez during the Winter '09 term at Broward College.

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