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. If the RNA primer consists of eight nucleotides, what is its base sequence?

Key Concepts

DNA Structure

DNA is composed of two strands forming a double helix, with each strand made up of nucleotides. Each nucleotide consists of a phosphate group, a sugar, and a nitrogenous base (adenine, thymine, cytosine, or guanine). The sequence of these bases encodes genetic information, and during replication, the strands separate to allow for the synthesis of new complementary strands.

RNA Primer Synthesis

During DNA replication, an RNA primer is synthesized by the enzyme primase. This primer is essential for DNA polymerase to initiate DNA synthesis, as it provides a free 3' hydroxyl group for the addition of DNA nucleotides. The RNA primer is complementary to the DNA template strand and is typically shorter than the DNA strands being synthesized.

Base Pairing Rules

Base pairing rules dictate how nucleotides pair in DNA and RNA. In DNA, adenine pairs with thymine (A-T) and cytosine pairs with guanine (C-G). In RNA, uracil replaces thymine, pairing with adenine (A-U). Understanding these rules is crucial for determining the sequence of the RNA primer based on the DNA template strand.