A Level Biology Practice Exam

What is the role of DNA polymerase during DNA replication?

1. to generate RNA strands

2. to catalyse the formation of phosphodiester bonds

3. to unzip the DNA strands

4. to repair DNA damage

The correct answer is: to catalyse the formation of phosphodiester bonds

During DNA replication, DNA polymerase plays a critical role in synthesizing new strands of DNA. Its primary function is to catalyze the formation of phosphodiester bonds between nucleotides, which are the building blocks of DNA. This process involves adding nucleotides to the growing DNA strand in a sequence that is complementary to the template strand. In the replication fork, DNA polymerase adds nucleotides one by one, ensuring that the new strand matches the template strand according to base pairing rules (adenine pairs with thymine, and cytosine pairs with guanine). The enzyme's activity creates a continuous DNA strand by linking the phosphate group of one nucleotide to the hydroxyl group of the sugar of the previous nucleotide, resulting in the formation of a stable sugar-phosphate backbone. Additionally, while the other options relate to important biological processes such as transcription (generating RNA strands) and DNA repair, they do not describe the specific function of DNA polymerase in DNA replication, which uniquely involves the synthesis of new DNA through the formation of phosphodiester bonds. Unzipping the DNA strands is primarily facilitated by helicase, not DNA polymerase, and DNA repair involves different enzymes tailored for correcting specific types of damage.