Nucleic Acids

• DNA

  Deoxyribonucleic acid, an important information carrying molecule. The genetic material in all living organisms.
• Genome

  Cells' entire genetic content
• Eukaryotic DNA

  • DNA found mainly in the nucleus (but some in chloroplasts & mitochondria)
• Prokaryotic DNA

  • DNA not enclosed in a membranous envelope
• RNA

  Ribonucleic acid, similar to DNA, mainly involved in synthesising proteins
• Ribosomes

  Formed from RNA and proteins, the protein builders of the cell
• mRNA

  Transfers genetic information from DNA in the nucleus to the ribosomes in the rest of the cell
• Nucleic acids

  Carry the cell's genetic code, instructions for the function of the cell, important for passing on information from generation to generation
• Monomers

  Nucleotides, the smaller units that make up nucleic acids
• Polynucleotides

  Nucleotides joined together to form nucleic acids like DNA or RNA
• Nucleotide

  Formed from a pentose sugar, nitrogen containing organic base & phosphate group
• Phosphodiester bond

  Bond formed between the sugar group of one nucleotide and the phosphate group of another
• Components of DNA nucleotides

  • Deoxyribose sugar
  • Phosphate group
  • Adenine
  • Cytosine
  • Guanine
  • Thymine
• Components of RNA nucleotides

  • Ribose sugar
  • Phosphate group
  • Adenine
  • Cytosine
  • Guanine
  • Uracil
• Purines


  Adenine and Guanine, have a double ring structure
• Pyrimidines


  Thymine and Cytosine, have a single ring structure
• DNA structure

  • Two polynucleotide chains arranged in a double helix, held together by hydrogen bonds between complementary base pairs, with the sugar and phosphate forming the backbone
• RNA structure

  • Relatively short polynucleotide chain, single strand, composed of ribonucleotides linked by phosphodiester bonds
• Base pairing in DNA

  Adenine + Thymine, Guanine + Cytosine
• Antiparallel


  The two polynucleotide strands run in opposite directions (5'-3' and 3'-5')
• DNA replication

  1. DNA unwinds and the two strands separate (as DNA helicase breaks hydrogen bonds between the strands)

  2. Free-floating nucleotides line up and form hydrogen bonds with complementary bases

  3. Each strand is used as a template to produce a new complementary strand

  4. DNA polymerase forms phosphodiester bonds between the nucleotides

  5. Two new DNA strands are synthesised (semi-conservative replication)
• DNA strands

  Carbon atoms of the sugar molecule numbered 1'-5', phosphate residue attaches to 5' and 3' carbons
• DNA polymerase

  Catalyses the condensation reaction between nucleotides, forming phosphodiester bonds
• Watson and Crick proposed models of DNA replication, including the semi-conservative model
• Meselson and Stahl's experiment with E. coli proved the semi-conservative model of DNA replication
• DNA NUCLEIC ACID:

  
• DNA SEMI CONSERVATIVE REPLICATION