DNA Replication Enzymes

Helicase - enzyme that splits the double helix by breaking hydrogen bonds

SSBs - single strand binding proteins, holds strands apart

RNA Primase - makes an RNA primer, starting point

DNA Polymerase III - builds complimentary DNA strand

Endonuclease - removes primers

DNA Polymerase I - replaces primers w/DNA, proofreads and fixes any mistakes

DNA Ligase - connects gaps (links)

DNA Structure

• Double strandded

• Made up of chains of nucleotides

  • Nucleotides are made of phosphate group, a sugar, and nitrogenous base

• Nitrogenous bases are G, C, A, and T

  • Thymine

  • Cytosine

  • Adenine

  • Guanine

• Sugar is deoxyribose sugar

• G/C and A/T are complimentary

• G/C are bonded with 3 h-bonds, A/T with two

• Purines (G/A) have two nitrogenous rings

• Pyrimidines (C/T/U) have one nitrogenous ring

RNA STRUCTURE

• Single stranded

• Made of four bases

  • Uracil

  • Cytosine

  • Adenine

  • Guanine

• Three types

  • Ribosomal (rRNA) - structural component of ribosomes

  • Messenger (mRNA) - used in transcription (coding for polypeptides)

  • Transfer (tRNA)

History & Discovery of DNA

• X-ray Crystallography (1950s): Rosalind Franklin and Maurice Wilkins utilized X-ray crystallography to capture images of DNA's structure, providing crucial data for later insights.

• Watson and Crick's Model (1953): James Watson and Francis Crick proposed the double helix structure of DNA, incorporating insights from Franklin and Wilkins' data.

• Nobel Prize (1962): Watson, Crick, and Wilkins were awarded the Nobel Prize in Physiology or Medicine for their discovery of the structure of DNA.

• Hershey-Chase Experiment - In the experiment, when the DNA of bacteriophages was labeled, it ended up inside the bacteria. But when only the protein coat was labeled, it stayed outside. This showed that DNA, not protein, carries the genetic information needed for viral replication.