Gene Expression — Transcription, Translation, and Mutations Explained | Chapter 17 of Campbell Biology

Welcome to Last Minute Lecture! This post covers gene expression, the fundamental process by which genetic information flows from DNA to protein, as detailed in Chapter 17 of Campbell Biology. Explore the central dogma, transcription, translation, mutations, and cutting-edge gene-editing technologies. Watch the full video summary below and subscribe for clear, chapter-by-chapter molecular biology guides!

Introduction: The Central Dogma of Molecular Biology

Gene expression describes how the genetic code in DNA is ultimately used to build proteins. The central dogma—DNA → RNA → Protein—summarizes the flow of genetic information in all living organisms, linking genotype to phenotype.

Transcription: DNA to mRNA

• Transcription: RNA polymerase reads a DNA template, synthesizing messenger RNA (mRNA).
• mRNA Processing in Eukaryotes: Addition of a 5′ cap, poly-A tail, and removal of introns via splicing. In prokaryotes, mRNA is translated immediately.

Translation: mRNA to Protein

• Translation: Ribosomes read mRNA codons, while transfer RNA (tRNA) delivers specific amino acids, building a polypeptide chain.
• Start Codon: AUG signals the start of translation; stop codons signal termination.
• Genetic Code: 64 codons specify 20 amino acids and stop signals; redundancy allows multiple codons for the same amino acid.

Mutations: Changes in the Genetic Code

• Point Mutations: Single nucleotide changes may cause silent, missense, or nonsense mutations.
• Frameshift Mutations: Insertions or deletions shift the reading frame, altering protein structure and function.
• Impact: Mutations can cause genetic diseases, such as sickle-cell anemia.

CRISPR-Cas9: Modern Gene Editing

• CRISPR-Cas9: A revolutionary technology that allows precise, targeted changes to DNA, offering potential cures for genetic disorders.

Key Terms and Glossary

• mRNA (messenger RNA): Carries genetic information from DNA to the ribosome.
• Codon: Three-nucleotide sequence coding for a specific amino acid.
• tRNA (transfer RNA): Brings amino acids to the ribosome during protein synthesis.
• Ribosome: Molecular machine that assembles proteins from mRNA instructions.
• Point Mutation: Single nucleotide change in DNA.
• Frameshift Mutation: Insertion or deletion altering the reading frame.
• CRISPR-Cas9: Technology for editing genes by cutting DNA at specific locations.

Conclusion: From Gene to Protein and Beyond

Chapter 17 of Campbell Biology illuminates the journey from DNA to protein, highlighting how gene expression determines the traits of all organisms. Understanding transcription, translation, and the effects of mutations is vital for genetics, biotechnology, and medicine. For a step-by-step breakdown, watch our full video summary and subscribe to Last Minute Lecture for more biology chapter explanations.

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