Biology Essentials: DNA and RNA

Introduction

• Presenter: Mr. Andersen
• Focus on DNA and RNA
• Example: Genetically engineered peanut plant resistant to corn stalk borer
• Genetic engineering allows DNA transfer between organisms

Key Concepts to Cover

1. History of DNA
2. DNA organization in chromosomes
3. Structure of DNA and RNA
4. Central Dogma (DNA -> RNA -> Proteins)
5. Genetic Engineering applications

History of DNA

Frederick Griffith Experiment (1928)

• Studied bacteria causing disease using mice
• Two strains of Streptococcus pneumoniae: Rough (harmless) and Smooth (virulent)
• Griffith found a "transforming factor" that turned harmless bacteria virulent

Avery-McCarthy-McLeod Experiments (1930s-40s)

• Investigated the transforming factor from Griffith's experiments
• Demonstrated that DNA was the transforming factor using enzyme digestion experiments
• Initial discoveries were largely ignored; DNA considered too simple

Hershey-Chase Experiment (1950s)

• Also known as the Blender Experiment
• Used bacteriophages to show that DNA, not proteins, was the hereditary material
• Used radioactive sulfur (in proteins) and phosphorus (in DNA) to track genetic material

Watson and Crick, and Others

• Watson & Crick: Credited with discovering DNA's double-helical structure
• Maurice Wilkins & Rosalind Franklin: Key contributions using X-ray crystallography
• Erwin Chargaff: Found bases A=T and G=C, known as Chargaff's Rule
• Discovery of the double helix: Nobel Prize awarded to Watson, Crick, and Wilkins

DNA Structure

• DNA organized into chromosomes in eukaryotic cells
• DNA wrapped around histone proteins forming nucleosome structures
• Eukaryotic chromosomes are linear
• Prokaryotic chromosomes are circular and not contained in a nucleus
• Prokaryotes also have plasmids (extra chromosomal DNA)
• Eukaryotic DNA contains non-coding regions (formerly called "junk DNA")

Central Dogma

• Describes the flow of genetic information:
  • DNA Transcription -> RNA Translation -> Protein Synthesis

Genetic Engineering

• Ability to manipulate and transfer DNA between different organisms
• Example: Bacteria engineered to produce human insulin
• Field is rapidly expanding with numerous applications