DNA+RNA

• DNA - deoxyribonucleic acid

  RNA - ribonucleic acid
• roles

  • storage and transport of genetic information
  • synthesis of proteins
• • DNA is a large and long molecule with a double helix shape
  • made from repeating monomers called (mono)nucleotides
• • nucleotides in DNA are made from 3 basic units

  1. deoxyribose (sugar) - pentose
  2. phosphate group - acidic and negatively charged
  3. nitrogenous base
• purines

  • double ringed structure
  • adenine
  • guanine
• pyrimidines

  • single ringed structure
  • thymine
  • cytosine
• • DNA is a large molecule with the following structure
  • 2 polynucleotide chains held together by hydrogen bonds that form between the bases
  • each chain runs in opposite direction to each other (antiparallel)
  • adenine and thymine (2 hydrogen bond)
  • cytosine and guanine (3 hydrogen bond)
• • DNA has a double helix structure and in every complete turn of the helix there are 10 base pairs
  • DNA is a stable molecule because phophodiester backbone provides protection to nitrogenous bases on the inside of double helix
  • DNA becomes more stable due to more C-6 bonds due to more hydrogen bonds
• • A and T , G and C form like this as they are complementary to each other
  • purines are larger than pyrimidines so having the combination of one large and one small molecule ensures the distance between the polynucleotide chains remains the same ensuring DNA is stable
• • function of DNA is to carry genetic information from one generation to the next and cell to cell
• • dna is stable helping to prevent changes to genetic information
  • 2 polynucleotide chains joined by weak hydrogen bonds allowing DNA molecules to seperate easily during replication
• • dna sequence codes for specific amino acid creating proteins
  • dna found in nucleus but too large and cant fit through pores in nuclear envelope
  • protein synthesis takes place in cells cytoplasm
• • RNAs job is to transfer genetic code from nucleus to cytoplasm
  • RNA is a polynucleotide
• RNA

  • has the bases g c a u
  • single stranded
  • shorter than dna
  • pentose sugar is ribose compared to dna which is deoxyribose
• • gain new cells through cell division 1. nuclear division (DNA copies itself and divides) 2. cell division ( where cell divides)
• stages of replication are

  1. hydrogen bonds between DNA bases broken by DNA helicase enzyme
  2. DNA strands unwind and separate
  3. activated complementary bases free in cytoplasm now bind to exposed bases on separate strands
  4. DNA polymerase enzyme joins activated nucleotides together forming new complem strand
  5. 2 identical DNA molecules formed with half original strand that’s why called semi conservative
  6. original strand acts as template for building of new strand
• • dna contains genes
  • genes are sections of dna that contain information for making polypeptides
  • polypeptides make proteins , proteins include enzymes which are responsible for controlling chemical reactions in the body
  • meaning that genes control all aspects of a living organism and any change in Dna sequence may result in different/non functioning protein
• • every 3 base pairs in DNA molecule codes for 1 amino acid
  • called a triplet code
  • sequence of amino acids that arise from triplet code within dna gives rise to different polypeptide chains which fold to create different proteins