nucleotides + nucleic acids

• replication - needed to create more DNA for cell division

  • occurs in the nucleus
  • helicase enzyme breaks hydrogen bonds to create 2 templates - a large section
  • DNA free nucleotides join to complimentary base pairing (A-T) on the existing strand, DNA polymerase assists
  • phosphodiester bonds between between nucleotides form for a new backbone, ligase enzyme assists
  • semi-conservative, one new strand, one original strand
• transcription - needed to code for amino acids to make proteins

  • occurs in the nucleus
  • RNA polymerase binds to section of DNA - helicase unzips, creating a template - a small section
  • RNA free nucleotides join to complimentary base pairings (A-U)
  • RNA polymerase joins them together forming a single mRNA strand that leaves the nucleus
• translation - needed to join amino acids to make proteins

  • occurs in cytoplasm
  • mRNA attaches itself to a ribosome, tRNA molecules carry amino acids to the ribosome
  • tRNA attaches by complementary base pairing, tRNA molecule has anticodon to mRNA
  • rRNA in ribosome catalyses formation of peptide bond between amino acids attached to tRNA molecule to join them together
  • ribosome moves along to create continous chain of amino acids
• similarities between replication, transcription and translation

  • both replication and transcription occur in the nucleus
  • helicase is involved in both, H-bonds broken
  • both transcription and translation help to make new proteins
  • free nucleotides in DNA/RNA/tRNA+mRNA join up
  • all 3 involve complementary base pairing
• differences between replication, transcription and translation

  • different types of free nucleotides join up
  • in transcription, the template is a small section, large section of 2 templates in replication
  • translation occurs in the cytoplasm, not the nucleus
  • single strand of mRNA formed in transcription, double strand of DNA formed in replication
  • uracil in RNA, thymine in DNA
  • clover shaped tRNA with anticodon
  • peptide bonds to join amino acids in translation, hydrogen bonds in transcription/replication
• role of ligase in dna replication

  assists dna polymerase + seals sugar-phosphate backbone
• role of helicase in dna replication

  unzips dna helix, breaks hydrogen bonds to separate base pairs to form 2 single strands which can act as a template
• why is the triplet codon degenerative

  there are more possible codon combinations than there are amino acids, meaning multiple codons can code for the same amino acid (except for methionine and tryptophan)
• what happens when two nucleotides in a polynucleotide strand join together

  • a phosphodiester bond forms between them
  • connecting the 5' phosphate group of one nucleotide and the 3' hydroxyl group of the next nucleotide
  • chain-like structure with a repeating sugar-phosphate backbone  
  • condensation reaction, water molecule released
• dna extraction

  1. cut, then mash up kiwi, add to water and add detergent + salt
  2. heat mixture in water bath - detergent + heat break down phospholipid bilayer to release dna for 15 mins
  3. cool in ice bath - prevents dna itself from breaking down
  4. filter mixture with filter paper - remove cell debris
  5. add protease to denature + remove proteins, leaving only dna
  6. add ice cold ethanol at an angle - nucleic acids are insoluble in ice-cold ethanol, so dna forms a precipitate
• ATP - 3 phosphate groups, 1 ribose sugar, 1 adenine

  ADP - 2 phosphate groups, 1 ribose sugar, 1 adenine (+ inorganic phosphate which is used to phosphorylate other compounds, increasing reactivity for cell cycle)
• ADP -> ATP

  • dna replication requires this process
  • energy is released when ATP is hydrolysed to form ADP, catalysed by ATP hydrolase
  • condensation of ADP is catalysed by ATP synthase
• suggest a suitable substance to release DNA from a crushed banana

  detergent + salt

  • detergent breaks down the nuclear envelope to release DNA by breaking cell membrane phospholipid bilayer
• state what structural detail of a polypeptide is altered by gene mutations

  sequence of amino acids
• explain why there are likely to be more differences between DNA base sequences than between amino acid sequences

  • only 20 amino acids
  • only 64 potential codon combinations
  • but billions of potential DNA combinations
  • far more likely to have differences due to quantity
• explain how the structure of DNA allows for replication

  • DNA has double helix structure, which can be unzipped to create 2 templates
  • complementary base pairings (A-T, G-C) allow for accurate copying of genetic info
  • weak hydrogen bonding between base pairs easily broken by helicase
  • sugar phosphate backbone provides stability and allows polymerase to attach to build new strands
  • antiparallel strands - polymerase builds the leading strand and the lagging strand in fragments, ensuring both strands are copied