Nucleic acids

• What does DNA and RNA Stand for and roles

  Deoxyribonucleic acid and ribonucleic acid

  both in living cells

  both needed to build proteins and both important information carrying molecules

  RNA ribose sugar has hydroxyl (OH) group at 2 position

  DNA deoxyribose sugar has hydrogen at 2 position
• function of dna 


  hold or store genetic informations and contains instructions for growth and development of all organisms

  double stranded
• function of RNA 


  transfer genetic code found in DNA out of nucleus and carry it to ribosomes in cytoplasm for protein synthesis

  due to hydroxyl group at 2 position more susceptible to hydrolysis

  single stranded
• what is a nucleotide

  DNA and RNA are polymers and made up of repeating units called nucleotides

  each nucleotide formed from a

  phosphate group

  pentose sugar

  and a nitrogen containing organic base
• What are the organic bases

  Adenine , cytosine guanine , uracil and thymine
• What are purines and pyrimidines

  Nitrogenous bases have two structural forms purines and pyrimidines

  adenine and guanine purines - double ring structure

  cytosine thymine and uracil pyrimidines as single ring structure
• How are nucleotides joined to form polynucleotides

  by a condensation reaction that occurs between the phosphate group of one nucleotide and pentose sugar of another . Forms phosphodiester bond
• Structure of DNA 


  Contains two Polynucleotide

  Each strand as alternating deoxyribose and phosphate to form phosphodiester bonds and sugar phosphate backbone

  has a 3 and 5 end

  hydrogen bonds form between complimentary base pairs AT and CG

  double helix structure
• structure of RNA 


  single polynucleotide strand

  base pairings AU GC

  shorter than DNA

  has a sugar phosphate backbone
• why was dna doubted to carry genetic code 


  due to its simple chemical composition many doubted that it could carry
• who confirmed double helix structure of DNA

  Watson and Crick in 1953 using Rosalind franklin x ray data
• What is semi conservative replication 


  Each new dna molecule produced contains one strand from original dna molecule and a new strand synthesised by the cell
• Importance of semi conservation

  Ensures genetic continuity and all cells produced in cell division inherit all their genes from parent . Important as division occurs regularly
• process of semi conservative replication 


  DNA helical unwinds and unzips helix by breaking hydrogen bonds

  each strand acts as a template for new strands

  free nucleotides join to bases by complimentary base pairings

  DNA polymerase joins new nucleotides as it catalyses condensation reaction to produce phosphodiester bonds

  original strand and new strand join by hydrogen bonding between base pairs