BIOL107 Lecture Notes - Lecture 29: Dna Ligase, Dna Polymerase Iii Holoenzyme, Helicase
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Biol 107 lecture #29 dna chemistry and replication pt. iv. Begins with the unwinding of the double helix at the origin of replication. Dna helicase unwinds it after the initiation protein attracts it. The unwound area is called a replication bubble and the end (y shaped) is called a replication fork. Primase synthesizes a short stretch of rna called the rna primer to which dna polymerase iii can begin adding nucleotides (in the 5" to 3" direction) Ssb"s (single stranded binding) proteins keep the bubble unwound by staying in the replication forks: elongation. Complementary base pairing occurs and dna polymerase iii catalyzes the actual joining of nucleotides. They are linked through phosphodiester bonds (adjacently) in a process called polymerization. Dna polymerase iii has no problem adding of the leading strand, adding 5" to 3". But in the lagging strand, it encounters a problem: the lagging strand is synthesized discontinuously in small fragments called okazaki fragments.