Classical and Modern Genetics

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

6. 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

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

8. DNA and the Birth of Molecular Genetics

9. 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)

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

11. DNA Structure

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

13. 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

14. The Genetic Code

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

16. 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

19. 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

20. 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

21. 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

22. 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

23. 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

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