DNA

• Meseison and stahi

  • grew bacteria (E-coli) with different N isotopes- semi conservative hypothesis
  • expose bacteria to N15 for many generations until exposed to a lighter N14
• Ligase


  makes sure all bonds are made
• point mutation


  a gene or point mutation is a change in the nucleotide sequence of a gene. This most commonly occurs during DNA replication
• DNA replication reasons


  reproduction and cell division
• DNA helicase


  breaks hydrogen bonds and unwinds molecule
• DNA polymerase 


  Forms covalent bonds between phosphates and sugars - oly done if nucleotides correctly paired up
• replication fork


  when strands split apart
• primed spot


  attaches to DNA polymerase
• semi conservative


  one strand stays the same
• Purine bases


  adenine and guanine
• pyramidine bases

  • thymine
  • uracil
  • cytosine
• schargraffs rule


  knowing the amount of one base - you'll know the amount of the rest of them
• transcription(in nucleus)

  • section of DNA unwinds and unzips (DNA helicase) - acts as a template
  • section of DNA transcribed (copied) to make mRNA (using RNA polymerase).
  • mRNA moves out of nucleus into cytoplasm where it attaches to ribosome. - Thymine replaced by uracil
• Translation(in cytoplasm)

  • tRNA picks up amino acids
  • one end of tRNA carries one amino acid and other end has a triplet code sequence which is complementary to codon on mRNA (anticodon)
  • once mRNA in cytoplasm and attached to a ribosome its read by tRNA
  • tRNA molecules line up against mRNA
  • peptide bonds made between amino acids