Unit 2) 8.1 Structure of DNA

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Structure of DNA

DNA is the chemical that determines inherited characteristics and it contains vast amounts of information in the form of genetic code.

Nucleotide Structure

A nucleotide (monomer) is made up of 3 basic components:

  • deoxyribose sugar
  • a phosphate group
  • organic base, belonging to 1 of 2 groups
    • single ring bases- cytosine (C) and thymine (T)
    • double ring bases- adenine (A) and guanine (G)


These 3 basic components are compined through condensation reactions; this creates a single nucleotide (mononucleotide)

2 mononnucleotides may be combined as a result of a condensation reaction between the deoxyribose sugar of 1 and the phosphate of the other. This creaates a dinucleotide.

Repeated condesation reactions like this forms a long chain of mononucleotides known as a polynucleotide.

DNA Structure

The DNA structure was worked out by Francis Crick and James Watson in 1953, who were followig the work of Rosalind Franklin on the X-ray diffraction patterns of DNA.

DNA is made up


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