Lecture on Gene Expression and Regulation

Introduction

• Discussed the concept of calling students "Penguins" due to their attire (tuxedos) symbolizing readiness for success.
• Mentioned resources available for AP Biology students, including Daily Reviews on Instagram and a 374-page review guide on a website.
• Available resources: FRQ Fridays, quizzes, games, and review PowerPoints.

Plan for the Session

• Focus on molecular genetics, operons, and biotechnology.
• Engage with 3 multiple-choice questions and 2 free response questions.
• Open for Q&A throughout the session.

Central Dogma of Molecular Biology

• DNA → RNA → Polypeptide
  • Replication: Copying DNA.
  • Transcription: DNA to RNA.
  • Translation: RNA to polypeptide.

Violations of the Central Dogma

• Retroviruses: RNA genome using reverse transcriptase to make DNA, e.g., HIV.

Differences in DNA Replication

• Eukaryotes: Multiple linear DNA strands within a nucleus.
• Prokaryotes: Single circular DNA strand in nucleoid.

Structure and Pairing

• Purines: Adenine, Guanine.
• Pyrimidines: Cytosine, Thymine.
• Bonding: A-T (2 bonds), C-G (3 bonds).

Transcription Process

• Occurs in the nucleus (eukaryotes) or nucleoid (prokaryotes).
• RNA Composition: Adenine, Uracil, Cytosine, Guanine.
• RNA Polymerase: Binds to promoter, separates strands, synthesizes RNA.

Post-Transcriptional Modifications (Eukaryotes)

• 5' Cap: Guanine cap for ribosome binding and nuclear export.
• Splicing: Removal of introns.
• Poly-A Tail: Extends mRNA lifespan.

Translation Process

• Ribosome Structure: Large and small subunits composed of rRNA and proteins.
• Initiation: Start codon AUG (methionine).
• Elongation: tRNA and mRNA base-pairing to add amino acids.
• Termination: Stop codons (UAA, UAG, UGA).

Mutations

• Point Mutations: Affect a single nucleotide.
  • Silent: No amino acid change.
  • Missense: One amino acid change.
  • Nonsense: Premature stop codon.
• Frameshift Mutations: Insertions/deletions that alter reading frame.

Regulation of Gene Expression

• Operons (Prokaryotes only): Promoter, operator, genes.
  • Repressible Operons: Default ON, turned OFF by product (e.g., trp operon).
  • Inducible Operons: Default OFF, turned ON by substrate presence (e.g., lac operon).

Biotechnology Techniques

• Gel Electrophoresis: DNA separation by size/charge.
• PCR (Polymerase Chain Reaction): Amplifies DNA fragments.
• Transformation: Introducing new DNA into bacteria.
• DNA Sequencing: Determining DNA sequence.

Practice Questions

• Examples include identifying DNA replication features, mutation consequences, and operon function.

Summary

• Recap of unit six topics: gene expression, regulation, and biotechnology.
• Encouraged students to use available resources and practice regularly.
• Open for additional questions about the lecture content.

Final Remarks

• Emphasized the importance of studying consistently up to the exam.
• Provided guidance on time management and study strategies.

These notes capture the core concepts and details covered in the lecture, providing a cohesive study guide for students preparing for exams on gene expression and regulation.