DNA Replication Overview

Introduction to DNA Replication

• Definition: DNA replication is the process by which a cell makes an identical copy of its DNA.

• Location: In eukaryotic cells, DNA replication occurs within the nucleus.

• Central Dogma Connection: DNA replication is the first step in the flow of genetic information, followed by transcription (DNA to RNA in the nucleus) and translation (RNA to Protein in the cytoplasm).

• Outcome: An unreplicated chromosome (a single DNA molecule) undergoes DNA synthesis and condensation to form a replicated chromosome, consisting of two identical sister chromatids joined at the centromere.

DNA Structure and its Implications for Synthesis

• Key Features: DNA is a double helix with specific structural dimensions:

  • Pitch of the helix: 3.4\text{ nm}

  • Distance between base pairs: 0.34\text{ nm}

  • Diameter of the double helix: 1\text{ nm}

  • The two strands are antiparallel, meaning they run in opposite 5' to 3' directions.

• Structure-Function Relationship: The double helix's specific base pairing (Adenine with Thymine, Guanine with Cytosine) provides a direct mechanism for copying genetic material. Watson and Crick observed this relationship.

Mechanism of DNA Replication: The Semiconservative Model

• Watson and Crick's Prediction: Their semiconservative model of replication posits that when a double helix replicates, each new daughter DNA molecule will consist of one parental (old) strand and one newly synthesized strand.

• Process:

  • The parent DNA molecule's two strands separate.

  • Each parental strand then serves as a template for the synthesis of a new, complementary strand.

  • The result is two