Biology 2.1

  • Created by: Rushil
  • Created on: 26-03-13 13:34

AQA BIO2 Chapter 1


  • Made up of a pentose sugar called deoxyribose.
  • Phosphate Group has a negative charge so DNA can be seperated.
  • The base of a nucleotide can be any one of 4 
    • Adenine
    • Guanine
    • Cytosine
    • Thymine
  • Adenine and Guanine are Purines.
  • Cytosine and Thymine are Pyrimidines


Single nucleotides undergo a condensation reaction to form a phosphodiester bond between the phosphate group of one nucleotiode and the deoxyribose sugar of another nucleotide, when this occurs between several nucleotides a polynucleotide strand is formed

A Sugar Phosphate Backbone is formed between the pentose sugars and the phosphate group.

Base Pairing

bases only pair if they are complementary, hydrogen bond form between complementary bases

A=T require 2 hydrogen bonds.

GC requires 3 hydrogen bonds.

Base pairs involve 1 purine base and 1 pyrimidine base.


comprised of 2 polynucleotide strands that run anti-parralel to each other, each strand has bases that are complementary to the other strand

hydrogen bonds hold the two strands together.


5' end is when the…


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