Gene Expression and Regulation: AP Biology Unit 6 Review

Introduction

Gene expression and regulation are essential for controlling how genetic information is utilized in cells. These processes involve transcription and translation, converting DNA into functional proteins. They are crucial across fields like medicine, agriculture, and biotechnology.

Key Concepts

• Central Dogma: Information flows from DNA to RNA to proteins.
• DNA: Blueprint for cellular processes, organized into genes coding for proteins.
• Transcription: Converts DNA information to mRNA via RNA polymerase.
  • Occurs in the nucleus (eukaryotes) or cytoplasm (prokaryotes).
• Translation: Synthesis of proteins using mRNA, ribosomes, and tRNA.
• Regulation: Ensures correct protein production.
  • Occurs at transcription, post-transcriptional, and translational levels.
• Epigenetic Factors: Influence gene expression without DNA sequence changes.

DNA Structure and Function

• DNA Structure: Double-stranded helix of nucleotides.
  • Nitrogenous bases: adenine, thymine, guanine, cytosine.
  • Complementary base pairing (A-T, G-C).
• Chromosomes: Coiled DNA structures storing genetic info.
• Genetic Code: Nucleotide sequences read in codons specifying amino acids.
• DNA Replication: Semiconservative, ensuring accurate genetic information transfer.

Transcription Process

• Initiation: RNA polymerase binds to DNA promoter.
• Elongation: RNA strand grows by complementary base pairing.
• Termination: RNA polymerase reaches termination sequence.
• RNA Processing: In eukaryotes, pre-mRNA is modified with a 5' cap, 3' poly-A tail, and splicing.

Translation and Protein Synthesis

• Ribosomes: Sites of protein synthesis, composed of rRNA and proteins.
• tRNA: Carries amino acids and has anticodons for mRNA codons.
• Translation Stages: Initiation, elongation, termination.
• Post-Translational Modifications: Affect protein structure and function.

Gene Regulation in Prokaryotes

• Transcription Regulation: Via repressors and activators.
• Lac Operon: Negative regulation example in E. coli.
• Trp Operon: Involves attenuation in response to tryptophan levels.
• CAP System: Positive regulation in response to glucose levels.

Gene Regulation in Eukaryotes

• Complex Regulation: Occurs at multiple levels.
• Transcriptional Regulation: Involves transcription factors and chromatin structure.
• Chromatin Structure: Euchromatin (active) vs. heterochromatin (inactive).
• Post-Transcriptional Regulation: Alternative splicing, RNA editing, miRNA.
• Translational/Post-Translational Regulation: Protein levels and activity fine-tuning.

Epigenetic Factors

• Epigenetics: Heritable expression changes without DNA sequence alteration.
• DNA Methylation: Generally silences genes.
• Histone Modifications: Affect chromatin accessibility and expression.
• Environmental Influences: Diet, stress, toxins affect epigenetic modifications.

Applications and Real-World Examples

• Medical Advances: Targeted therapies based on gene expression.
• Epigenetic Therapies: For diseases like cancer.
• Agricultural Biotechnology: Genetically modified crops.
• Synthetic Biology: Design and optimize biological systems.
• Forensic Science: DNA evidence analysis.
• Research: Insights from model organisms like mice and fruit flies.