Structure of DNA and RNA

Topic 2.6

Essential idea: The structure of DNA allows efficient storage of genetic information.


2.6.U1 The nucleic acids DNA and RNA are polymers of nuclei acids

DNA nucleotides are made up of a sugar (deoxyribose), base (adenine, guanine, cytosine, thiamine) and phosphate.

dna structure link dna structure animation
DNA nucleotide structure

RNA nucleotides are made up of a sugar (ribose), base (adenine, guanine, cytosine, uracil) and phosphate.

RNA nucleotide structure

2.6.U2 DNA differs from RNA in the number of strands, the base composition and the type of pentose

Using the figure below compare the structures of RNA and DNA. Place your mouse pointer on the figure to show the differences.

rna vs dna structure

2.6.U3 DNA is a double helix made of two antiparallel strands of nuculeotides linked by hydrogen bonding between                      complementary base pairs

How are DNA nucleotide joined together?

DNA nucleotides are joined together in a condensation reaction which produces water and a covalent bond between the two nucleotides. The figure below illustrates a condensation reaction between two DNA nucleotides. These reactions are continued until a single-strand of DNA is composed.

Nucleotide Condensation
Structure of a DNA strand

How is a DNA double helix formed?

The DNA double helix is formed by using complementary base pairing (i.e., adenine bonds thymine and cytosine bonds guanine). In the figure below key points include complementary base pairing held together by hydrogen bonding in the sugar-phosphate backbone.

DNA structure


2.6.A1 Crick and Watson's elucidation of the structure of DNA using model making

Elucidation of DNA structure Elucidation of DNA

2.6.S1 Drawing simple diagrams of the structure of single nucleotides of DNA and RNA, using circles, pentagons and rectangles                      to represent phosphates, and pentoses and bases

DNA nucleotide structure
RNA nucleotide structure
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