Replication

• Semiconservative


  Each strand of DNA in the double helix acts as a template strand for a new complimentary strand
• DNA polymerase


  Enzyme responsible for synthesizing DNA by adding complimentary nucleotides to the 3' end of a strand that follows a preexisting one. Proofreads its work over and cannot start a new strand from nothing (needs a primer)
• Primer


  Preexisting chain or short strand of nucleotides necessary for polymerase to start its work
• Nucleotides get the energy to attach themselves to a chain through releasing two phosphate groups, along with a lot of energy
• Origins of replication


  Specific spot on DNA with a start codon that replication has to begin from
• Replication forks


  2 Y-shaped proteins on DNA that open up a replication bubble for new DNA
• Replication bubble


  When DNA slowly gets unzipped by each strand getting a new complimentary strand
• Helicase


  Enzyme to load off at the origin of replication, and moves the replication forks away from each other (expanding the bubble) by undoing the hydrogen bonds between complimentary nucleotides
• Single strand binding proteins


  Proteins that coat the separated strands of DNA near the forks to make sure that they don't come back together
• Primase


  RNA primer enzyme 5-10 nucleotides long that attaches to the start codon. Its end provides a hydroxyl group (3' end) for the new nucleotides polymerase will put down
• Template strand

  DNA strand that another strand is getting built off of
• Leading strand

  DNA strand in the replication fork that gets added onto in the 5' - 3' direction that gets appended smoothly and continuously
• Lagging strand


  DNA strand in the replication fork going in the 3' - 5' direction. The Polymarase has to keep backtracking as new segments are exposed by the helicase, meaning it attaches nucleotides in a way that leaves okazaki fragments
• Okazaki fragments


  Small fragments that the DNA on the lagging strand is placed in
• Sliding clamp


  Ring-shaped protein that holds down DNA polymerase III as it synthesizes DNA, stops it from floating off when it makes a new okazaki fragment on the leading strand
• Topoisomerase


  Prevents the DNA ahead of the replication forks from getting too tightly wound by creating little nicks that loosen the tension (they get fixed right after)
• DNA ligase


  Enzyme that fixes up the nicks left by topoisomerase once the primers are replaced
• Chargaff rules


  Idea that A T C and G aren't equal, but A and T, and C and G are