DNA replication diagram drawing takeaway notes

Key Idea: that 5’ → 3’ shit

• In DNA replication nucleotides are always being added to the 3’ end of the growing strand

  • 5’ end of new nucleotide is attached to the 3’ end of the pre-existing strand through hydrolyzation → covalent (phosphodiester) bond forms → two phosphate groups are released

• Leading Strand

  • The leading strand is being replicated toward the fork

  • Remembering that DNA is antiparallel → the new nucleotides will run in the opposite direction

    • Rep fork is in the direction of the 5’ end of the original DNA

    • primase attaches at the 3’ end of the specific section of the DNA @ the point of origin

• Lagging Strand

  • Lagging strand is being replicated away from the fork

  • Again, the antiparallel structure of DNA means that new nucleotides run in the opposite direction from that of the original

    • Rep fork is in the direction of the 3’ end of the original DNA → 5’ end of the new DNA, would mean that replication would go from 3’ → 5’

      • but DNA polymerase can only synthesize the DNA from 5’ → 3’

      • additional primase adds nucleotides and Okazaki fragments (tiny subsections of DNA) are created following the 5’ → 3’ direction

Vocabulary

• Okazaki fragments

  • small sections of nucleotides that are added in the lagging strand

• (RNA) Primer

  • 5-10 RNA nucleotides added to the 3’ OH at the point of origin (what allows for DNA polymerase to add more nucleotides) \

• Primase

  • the enzyme that adds the RNA nucleotides

• Helicase

  • the unzipper for the DNA

• Topoisomerase

  • prevents bunching up/supercoiling of DNA so that helicase can unzip

    • by breaking phosphodiester bonds ? (verify)

  • comes BEFORE helicase

  • telephone cord analogy

• SSBP’s

  • wet clay base analogy

  • keeps the strands of DNA temporarily apart during replication as they will want to remerge due to h-bond interactions