DNA Replication

Definition

DNA replication is the biological process by which a cell makes an identical copy of its DNA before cell division. This process is crucial for ensuring that each daughter cell receives an exact copy of the genetic material, enabling proper functioning and growth. DNA replication occurs during the S phase of the cell cycle and involves several key enzymes and proteins that work together to unwind the double helix and synthesize new strands of DNA.

5 Must Know Facts For Your Next Test

1. DNA replication follows a semi-conservative model, meaning each new double helix consists of one original strand and one newly synthesized strand.
2. Replication begins at specific locations on the DNA molecule known as origins of replication, where the DNA is first unwound.
3. The leading strand is synthesized continuously in the direction of the replication fork, while the lagging strand is synthesized in short segments.
4. DNA ligase is essential for joining Okazaki fragments on the lagging strand to create a continuous DNA strand.
5. Errors during DNA replication can lead to mutations, but cells have proofreading mechanisms to correct many of these mistakes.

Review Questions

• Explain how enzymes like helicase and polymerase contribute to the process of DNA replication.
  • Helicase plays a crucial role in DNA replication by unwinding and separating the two strands of the double helix, creating a replication fork. Once the strands are separated, polymerase synthesizes new DNA strands by adding nucleotides that are complementary to each template strand. Together, these enzymes ensure that the genetic information is accurately duplicated for both daughter cells during cell division.
• Discuss the differences between leading and lagging strand synthesis during DNA replication.
  • Leading strand synthesis occurs continuously in the direction of the replication fork, allowing for a smooth addition of nucleotides. In contrast, lagging strand synthesis is more complex as it occurs in short segments called Okazaki fragments, which are synthesized away from the replication fork. This requires additional steps, including the use of DNA ligase to join these fragments together, creating a continuous strand once replication is complete.
• Evaluate how errors in DNA replication can affect genetic information and organismal development.
  • Errors during DNA replication can result in mutations, which may alter the genetic information passed on to daughter cells. These mutations can have varying effects on an organism, ranging from benign changes to serious consequences like genetic diseases or developmental issues. The ability of cells to recognize and correct these errors through proofreading mechanisms is critical for maintaining genetic stability and preventing detrimental effects on growth and function.

Related terms

Helicase: An enzyme that unwinds and separates the two strands of the DNA double helix during replication.

Polymerase: An enzyme that synthesizes new DNA strands by adding nucleotides complementary to the template strand during replication.

Okazaki Fragments:

Short segments of newly synthesized DNA on the lagging strand that are later joined together by DNA ligase.