Match each of the following protein functions during DNA replication with its correct protein on the figure: 1. Unwinds the DNA double helix 2. Prevents the separated DNA strand from reannealing 3. Helps DNA polymerase to be processive (to continue on the DNA) 4. Creates the RNA primer 5. Synthesizes new DNA strand 6. Unknown protein function
The Correct Answer and Explanation is:
Correct Matching of Protein Functions During DNA Replication:
- Helicase – Unwinds the DNA double helix
- Single-Stranded Binding Protein (SSB) – Prevents the separated DNA strand from reannealing
- Sliding Clamp (e.g., PCNA in eukaryotes, β-clamp in prokaryotes) – Helps DNA polymerase to be processive
- Primase – Creates the RNA primer
- DNA Polymerase – Synthesizes new DNA strand
- Unknown Protein – Unknown protein function
Explanation
DNA replication is a fundamental biological process in which the genetic material is duplicated before cell division. This complex, highly regulated process involves several key proteins, each with a specific role.
Helicase initiates replication by unwinding the DNA double helix. This enzyme breaks the hydrogen bonds between the base pairs, producing two single-stranded DNA templates. The unwinding process creates tension ahead of the fork, which is usually resolved by topoisomerases (not listed here).
Once the strands are separated, single-stranded binding proteins (SSBs) attach to the exposed DNA. Their role is crucial in stabilizing the single strands and preventing them from reannealing or forming secondary structures that could impede the replication machinery.
Primase, a type of RNA polymerase, synthesizes short RNA primers on both the leading and lagging strands. These primers provide the necessary 3′ hydroxyl group that DNA polymerase requires to begin DNA synthesis.
DNA polymerase then adds deoxyribonucleotides to the RNA primer, extending the DNA strand in a 5′ to 3′ direction. On the leading strand, this occurs continuously, while on the lagging strand, it occurs discontinuously in short fragments known as Okazaki fragments.
To enhance the efficiency and fidelity of replication, the sliding clamp encircles the DNA and tethers the DNA polymerase to the template strand. This increases the processivity of the enzyme, allowing it to synthesize long stretches of DNA without dissociating.
Lastly, the unknown protein listed has not yet been characterized in terms of function. It may have a regulatory, structural, or accessory role yet to be discovered.
Each protein operates in coordination, ensuring accurate and efficient replication of the genome.
