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Classical and Modern Genetics

Explore the fascinating world of genetics through classical experiments by Mendel, DNA structure, transcription of DNA, protein synthesis, mutations, gene expression control, and the impact of viruses like HIV. Understand the universal genetic code shared by all living things.

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Classical and Modern Genetics

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  1. Classical and Modern Genetics Chapter 23 Great Idea: All living things use the same genetic code to guide the chemical reactions in every cell.

  2. Chapter Outline • Classical Genetics • DNA and the Birth of Molecular Genetics • The Genetic Code

  3. Classical Genetics

  4. Classical Genetics • Mendel • Basic laws of inheritance • Classic pea plant experiments • Purebred • Hybrid • Results • First generation • Second generation • Gene • Dominant • Recessive

  5. Rules of Classical Genetics • Traits (genes) are passed from parent to offspring • mechanism unknown • Two genes for each trait • One from each parent • There are dominant and recessive genes • Dominant expressed

  6. Qualitative versus Quantitative Genetics • Qualitative • observational • Quantitative • Predictive model • Used to trace genetic disease

  7. DNA and the Birth of Molecular Genetics

  8. Nucleotides: The Building Blocks of Nucleic Acids • Nucleotide • Three molecules • Sugar • DNA: deoxyribose • RNA: ribose • Phosphate ion • Base • Adenine (A) • Guanine (G) • Cytosine (C) • Thymine (T)

  9. DNA Structure • Join nucleotides • Alternating phosphate and sugar • DNA • 2 strands of nucleotides • Joined by base pairs • Bonding pattern • Adenine:Thymine • Cytosine:Guanine

  10. DNA Structure

  11. RNA Structure • Differences • One string of nucleotides • Sugar is ribose • Thymine replaced by uracil • Uracil (U) bonds with adenine

  12. The Replication of DNA • DNA replication • Occurs before mitosis & meiosis • Process • DNA double helix splits • New bases bond to exposed bases • Result • Two identical DNA strands

  13. The Genetic Code

  14. Transcription of DNA • Transcription • Information transport • Uses RNA • Process • Unzip DNA • RNA binds to exposed bases • RNA moves out of nucleus (mRNA)

  15. The Synthesis of Proteins • tRNA • Reads message • Structure • Amino acid • 3 bases • Process • mRNA moves to ribosome • rRNA aligns mRNA and tRNA • tRNA matches codon on mRNA • Amino acid chain forms • Basis for protein

  16. Protein synthesis cont. • One gene codes for one protein • Protein drives chemical process in cell • DNA • Introns • Exons • All living things on Earth use the same genetic code

  17. Mutations and DNA Repair • Mutations • Change in DNA of parent • Causes • Nuclear radiation • X-rays • UV light • DNA Repair • 10,000 ‘hits’ per day • Cells repair damage

  18. Why Are Genes Expressed? • Gene control • Turning genes on and off • Each cell contains same genes • Not all cells have same function • Certain genes activated • Scientists currently studying how

  19. Viruses • Virus • Not alive • No metabolism • Cannot reproduce on own • Structure • Short DNA or RNA • Protein coating • How it works • Taken into cell • Takes over cell • Produces more copies • Kills cell

  20. HIV • Human Immunodeficiency Virus (HIV) • Contains RNA • Codes back to DNA • DNA incorporated into cell • Makes new viruses • Cell dies • Complex • Two protein coats • Outer coat fits T cell receptors • Inner coat encloses RNA

  21. Viral Epidemics • Viruses • Cannot use medication • Use vaccination • Viruses evolve rapidly • HIV • Influenza • SARS • Bird flu

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