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DNA Replication

This resource provides a comprehensive review of DNA structure and the mechanisms of DNA replication. It introduces DNA (Deoxyribonucleic Acid) as a double helix and the foundation for all living organisms, responsible for protein synthesis and traits like eye color and heart function. The structure is built from nucleotides consisting of a phosphate group, a 5-carbon sugar, and nitrogen bases (Adenine, Thymine, Guanine, Cytosine). The replication process involves unwinding the DNA double helix, forming replication forks, and synthesizing new strands. This occurs enzymatically during the S phase of interphase, resulting in two identical DNA molecules.

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DNA Replication

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  1. Unit 4 Part 1 DNA Replication

  2. Review of DNA structure • Name: Deoxyribonucleic Acid • Shape: Double Helix • Function: • Basis for all living things • Makes proteins which make traits eye color, nose shape, heart function. • Structure: Made up of repeating units called nucleotides. Nucleotides: (3 Parts) • Phosphate group • 5 Carbon sugar • Sugars and phosphate are held together by a covalent bond. • Nitrogen base • There are 4 nitrogen bases – Hydrogen bonds • Adenine Guanine • Thymine Cytosine

  3. Nitrogen Bases • Nitrogen bases pairing together is what makes the double helix shape. • The 4 nitrogen bases are grouped together • Pyrimidines • Cytosine • Thymine • Purines • Adenine • Guanine • Only a purine can pair with a pyrimidine • Adenine – Thymine • Guanine – Cytosine

  4. Complementary Bases • In order to make the double strand the N-bases pair up with an existing strand: • What would the complementary strand be for the following DNA sequence: • AAA TCG GTA CCA TGA CAG GCC TGC AAT • __________________________________________

  5. DNA Replication 1. The Double Helix unwinds and unzips by breaking the Hydrogen bonds between the nitrogen bases. • An enzyme called DNA Helicase does this. 2. The 2 strands separate and form a replication fork . • Place where the new nucleo.tideswill be added.

  6. DNA Replication cont’d. 3. New nucleotides are added to the unwound strands (template or parent strands) following the base pairing rules. • DNA Polymerase does this. 4. As DNApolymerasemoves along the strands, 2 new double helixes are formed. 5. Enzymes continue adding nucleotides until it reaches a signal for it to detach.

  7. DNA Replication Review • Occurs during the S phase of interphase. • Process by which 2 identical strands of DNA are created. • First the double helix unwinds and unzips-DNA Helicase. • New nucleotides are added to the existing strands. • DNA replication is complete. • Once the DNA (chromatin) condenses into chromosomes they would be replicated chromosomes.

  8. DNA Replication Video • DNA Replication Video

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