Question

Problems to consider with DNA replication:

Problem: DNA Polymerase III can’t initiate replication on single-stranded DNA

Solution:

Answer 1

DNA polymerase can only extend a nucleotide sequence from a free 3' OH group and can not initate a new nucleotide synthesis on its own.

This problem is solved by an enzyme called Primase. Primase synthesize RNA primers complementary to the DNA. These primers are 8 to 12 nucleotide sequences. Once primers are synthesized, the DNA polymerase 3 can start extending the nucleotide chain from the 3' OH group of the last nucleotide of primer. After the replication is complete, these RNA primers are removed by DNA polymerase 1 and are replaced with DNA sequences.

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