Nucleotides, DNA & RNA

• DNA holds genetic information.
• RNA transfers genetic information.
• DNA nucleotides are composed of a deoxyribose sugar, a phosphate group and one of the nitrogenous organic bases adenine, cytosine, guanine or thymine.
• RNA nucleotides are composed of a ribose sugar, a phosphate group and one of the nitrogenous organic bases adenine, cytosine, guanine or uracil.
• Nucleotides join together by phosphodiester bonds formed during condensation reactions.
• Semi-conservative replication of DNA.

  • DNA helicase, causes the two strands of DNA to separate and unwind, breaking the hydrogen bonds between the complementary bases.
  • One of the strands is used as the template and the complementary base pairing occurs between the template strand and free nucleotides.
  • Then the enzyme DNA polymerase joins the complementary bases together by forming phosphodiester bonds. This results in two identical strands of DNA being formed.
• Types of RNA:

  • Messenger RNA (mRNA)
  • Transfer RNA (tRNA)
  • Ribosomal RNA (rRNA)