Polarity continued Note that the two DNA strands go in opposite directions 5 to

Polarity continued note that the two dna strands go

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Polarity continued Note that the two DNA strands go in opposite directions 5’ to 3’ and 3’ to 5’ This is called antiparallel structure 5’ 3’
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DNA Structure Video
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Origins of replication DNA is a huge molecule. It must have an efficient method for replicating (copying) itself Bubbles, daughter strands, and replication forks: DNA replicates by splitting into single strands in numerous places forming “bubble-like” structures. This allows the huge molecules to copy themselves efficiently. H-bonds are easily broken to allow single- stranded “bubbles” to form. The bubbles eventually run together to connect the sections into a fully copied new strand
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The replication fork The new strand is formed 5’ to 3’. This directionality makes it easy for one of the new strands to replicate. It’s called the “Leading Strand.” It goes toward the fork as the template strands come apart at the fork, The other strand is called the “Lagging Strand.” This strand is formed in pieces in the opposite direction, away from the fork. Okazaki Fragments are small bits of new DNA that must added toward the fork as it opens. These strands must be ligated (joined) together. The fork is formed as the template strands come apart The template strands are now farther apart
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Priming the reaction DNA polymerase is the enzyme that adds nucleotides to the growing DNA strand. Before it can start adding nucleotides, it needs a preliminary sequence of nucleotides to attach its first nucleotide to. This preliminary strand, called the RNA primer , consists of RNA nucleotides. It is laid down by the enzyme Primase . Eventually, the RNA primer strand is replaced with DNA nucleotides RNA primer (RNA) Primase RNA replaced with DNA later
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The key enzymes Primase provides the RNA primer strand to which new nucleotides are added. DNA Polymerase adds DNA nucleotides starting at the end of the RNA primer strand DNA Ligases join Okazaki fragments together DNA Polymerase replaces RNA nucleotides in the primer sequence with DNA nucleotides
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Other proteins/enzymes assist the process Single-strand binding proteins stabilize unwound DNA by holding strands apart. Helicases unwind the helix and separate strands to form the replication bubble
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Ta-da: Review video
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DNA Replication Video 1
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DNA Replication Video 2
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  • Fall '19
  • DNA, Frederick Griffith

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