Assume that the sequence of bases shown below is present on one nucleotide chain of a DNA duplex and that the chain has opened up at a replication fork. Synthesis of an RNA primer occurs on this template starting at the base that is underlined. In the intact RNA primer, which nucleotide has a free 3'-OH terminus? 3'.......GGCTACCTGGATTCA....5'

Key Concepts

DNA Replication

DNA replication is the biological process by which a cell duplicates its DNA, allowing genetic information to be passed on during cell division. It involves unwinding the double helix at the replication fork, where each strand serves as a template for synthesizing a new complementary strand. This process is essential for cell growth and reproduction.

RNA Primer

An RNA primer is a short strand of RNA that provides a starting point for DNA synthesis during replication. It is synthesized by the enzyme primase and is necessary because DNA polymerases can only add nucleotides to an existing strand. The primer is later removed and replaced with DNA nucleotides to complete the new DNA strand.

3'-OH Terminus

The 3'-OH terminus refers to the end of a nucleic acid strand that has a free hydroxyl (-OH) group attached to the third carbon of the sugar molecule. This free 3'-OH group is crucial for DNA and RNA polymerases, as it is the site where new nucleotides are added during synthesis, allowing the strand to elongate in the 5' to 3' direction.