DNA

• composed pf 2 long polynucleotide chains
• two strands twisted into double helix
• sugar-phosphate backbone provides strength and stability
• sugar phosphate backbone protects bases / protects hydrogen bonds
• long/large molecule can store lots of information
• helix / coiled compact so a lot of information can be stored in a small place
• base sequence codes for amino acids / protein
• double stranded replication can occur semi-conservatively so both strands can act as templates
• weak hydrogen bonds can be broken easily and many make it strong and stable
• nucleotide structure

  A) phosphate

  B) base

  C) pentose sugar

  
• The bases are amine, thymine, adenine and cytosine
• purines are adenine and guanine. they have 2 hydrogen bonds
• cytosine and guanine are pyrimidine and have 3 hydrogen bonds
• DNA strands are antiparallel
• one strand runs '5 to '3 and one 3' to 5'