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DNA Replication – the process. DNA replication. When a cell divides the DNA has to copy itself (m&m!) Because the DNA contains important information the DNA has to copy itself without making mistakes. DNA replication - eukaryote. The DNA strand starts by ‘unzipping’.
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DNA replication • When a cell divides the DNA has to copy itself (m&m!) • Because the DNA contains important information the DNA has to copy itself without making mistakes.
DNA replication - eukaryote • The DNA strand starts by ‘unzipping’. • The two strands break apart at the weak hydrogen bonds. The enzyme helicase does this. • Nucleotide bases now attach to the unzipped strands to make new strands.
DNA replication • Animation • Nucleotides are assembled in opposite directions from the 5’ to the 3’ by the enzyme DNA polymerase. • Replication forks move until whole strand is copied. • New strands rewind – semiconservative.
DNA replication • Another animation • Okazaki fragments • Because DNA antiparallel one side can be continously copied and the other is copied in fragments. The fragments are turned into one strand by the enzyme ligase.
DNA replication • Error rate in copying of one in 10000 base pairs but there is a system of ‘proof reading’.