Stages of replication:
- In the first stage, no replication has taken place but the strands of DNA in the parent chromosomes are being unwound by the enzyme helicase. Another enzyme known as DNA gyrase relieves the strain caused by unwinding and cutting the strands.
- In the second stage, new DNA for the daughter cell is formed by an enzyme complex called DNA polymerase and other proteins that cause the two strands to break apart
- In the third stage, the new double helix DNA contains one of the original DNA strands from the parent and the newly synthesised strand. The newly joined DNA strands are rewound into the double-helix shape; they are then recoiled around histone proteins and further wrapped up to form chromatids
Image: http://en.wikipedia.org/wiki/Semiconservative_replication
Details on replication models: Biozone student workbook, AQA biology AS CGP
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