Monday, November 3, 2008

Q: Explain why the two strands of DNA elongate in opposite directions

The two strands of DNA are anti parallel. Their 5' to 3' direction is in opposite direction. As the active site of the enzyme DNA polymerase III only recognizes the 3' end of a DNA nucleotide, free nucleotides can only be added in the 3' direction. Hence each of the two strands of DNA can only elongate in different directions when undergoing replication.

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