DNA replication

Definition

DNA replication is the biological process of producing two identical copies of a DNA molecule from a single original DNA strand. This process is crucial for cell division, ensuring that each new cell receives an exact copy of the genetic material. It is fundamental for both prokaryotic and eukaryotic organisms, facilitating growth, development, and repair by accurately duplicating the genetic instructions required for life.

5 Must Know Facts For Your Next Test

1. DNA replication occurs in a semi-conservative manner, meaning each new DNA molecule consists of one original strand and one newly synthesized strand.
2. In prokaryotes, DNA replication typically begins at a single origin of replication and proceeds bidirectionally, while eukaryotic cells have multiple origins of replication on each chromosome.
3. The process of DNA replication involves several key enzymes, including helicase, primase, DNA polymerase, and ligase, each playing distinct roles in unwinding, synthesizing, and joining DNA strands.
4. Eukaryotic DNA replication is more complex due to the presence of linear chromosomes and associated proteins that package the DNA into chromatin.
5. Errors during DNA replication can lead to mutations, but cellular mechanisms like proofreading by DNA polymerase and mismatch repair help maintain genetic integrity.

Review Questions

• How does the process of DNA replication differ between prokaryotic and eukaryotic cells?
  • DNA replication in prokaryotic cells occurs at a single origin of replication and proceeds bidirectionally along the circular chromosome. In contrast, eukaryotic cells have multiple origins of replication on their linear chromosomes, allowing for simultaneous replication of different segments. Additionally, the complexity of eukaryotic DNA packaging into chromatin requires specific regulatory proteins that are not present in prokaryotes.
• Explain the role of key enzymes involved in DNA replication and how they contribute to the overall process.
  • Several key enzymes play essential roles in DNA replication. Helicase unwinds the double helix, creating two separate strands. Primase lays down RNA primers to provide starting points for synthesis. DNA polymerase adds nucleotides to the growing strand and also has proofreading ability to correct errors. Finally, ligase joins Okazaki fragments on the lagging strand, ensuring a continuous DNA molecule is formed.
• Evaluate how errors during DNA replication can affect genetic stability and discuss the mechanisms that prevent these errors.
  • Errors during DNA replication can lead to mutations, which may disrupt gene function or lead to diseases such as cancer. The accuracy of DNA replication is enhanced by proofreading activity of DNA polymerase that corrects mismatched bases during synthesis. Moreover, after replication, mismatch repair mechanisms identify and correct any remaining errors. Together, these systems help maintain genetic stability across generations.

Related terms

Helicase: An enzyme that unwinds and separates the two strands of DNA during replication, creating a replication fork.

DNA Polymerase: An enzyme responsible for adding nucleotides to the growing DNA strand during replication and proofreading the new DNA to ensure accuracy.

Okazaki Fragments: Short sequences of DNA synthesized discontinuously on the lagging strand during DNA replication, which are later joined together by DNA ligase.