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Warm Up:

Warm Up:. Place in order from largest to smallest: Chromosome Gene Cell Nucleus. M odern genetics. DNA. D eoxyribo n ucleic a cid Heredity information is encoded in DNA. James Watson and Francis Crick. April 1953 Double helix model for DNA. Rosalind Franklin.

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Warm Up:

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  1. Warm Up: • Place in order from largest to smallest: • Chromosome • Gene • Cell • Nucleus

  2. Modern genetics

  3. DNA • Deoxyribonucleic acid • Heredity information is encoded in DNA

  4. James Watson and Francis Crick • April 1953 • Double helix model for DNA

  5. Rosalind Franklin • X-ray diffraction photographs of DNA

  6. DNA Structure • Sugar-phosphate backbone • Nitrogenous bases • Guanine • Cytosine • Thymine • Adenine

  7. Base Pairing Rules • Good Couple, Always Together

  8. Fill in the missing bases… A A C C A C

  9. RNA • Ribonucleic acid • Contains ribose instead of deoxyribose • Single stranded • Nitrogenous bases • Guanine • Cytosine • Uracil • Adenine

  10. DNA Replication and Repair • Each strand is complementary • Each strand stores the information necessary to reconstruct the other • Therefore each strand is called a template

  11. DNA Replication • Begins at a special site(s) called origin of replication • Proteins that initiate DNA replication recognize specific base sequences • The two strands are separated by helicase and form a replication bubble

  12. Primers • Short strands of RNA or DNA that initiate replication

  13. Replication continued • DNA polymerase elongates new strands of DNA at replication forks • Individual nucleotides align with complementary nucleotides of template strand • 50 per second in humans

  14. DNA is antiparallel • DNA polymerase only adds nucleotides to 3’ end • DNA ligase joins Okazaki fragments

  15. Proofreading and Repairing DNA • Highly accurate due to specificity of base pairing • DNA polymerase proofreads each nucleotide against its template • If incorrect, DNA polymerase removes the nucleotides and resumes synthesis

  16. Mutagens • Agents that cause mutations • Radioactive emissions • X-rays • Ultraviolet light • If this mutations occur in gametes (egg and sperm), they are passed to offspring

  17. Genetic Code • Scientists recognized a problem: there were only 4 nucleotide bases to specify 20 amino acids • REMEMBER: amino acids are the building blocks of proteins • Codons: triplets of nucleotide bases

  18. Genes • Provide instructions for making proteins • 2 major steps • Transcription • Translation

  19. Transcription • Synthesis of RNA under direction of DNA (occurs in nucleus) • RNA molecules is called messenger RNA (mRNA) • Carries genetic message from DNA to ribosomes • REMEMBER: ribosomes are the site of protein synthesis

  20. Helicase T A A A T U C G G C G G T A A C G G

  21. Translation • Synthesis of a polypeptide occurring under the direction of mRNA • Occurs at ribosomes

  22. AUG= Met (start)

  23. Initiation: AUG (start) codon • Elongation: • anticodons match up with mRNA codons • tRNA carries appropriate amino acid • Termination: UAA, UAG, UGA (stop) codons • Occurs at ribosome

  24. tRNA

  25. DNA TACAAAACCATT • Codon AUGUUUUGGUAA *mRNA • Amino acid Met-Phe-Trp

  26. DNA T C C C C G G A A A A A Transcrption A U U U U U G G G G C C mRNA Translation protein Trp Phe Gly Ser

  27. Point Mutations-single base substitution • A nonsense mutation is one in which the change in DNA base sequence results in a change in the mRNA that translates into premature chain

  28. Add one or more extra nucleotides into the DNA

  29. Remove one or more nucleotides from the DNA • Like insertions, these mutations can alter the reading frame of the gene

  30. Single nucleotide is changed, resulting in a codon that codes for a different amino acid • This can render the resulting protein nonfunctional

  31. Substitution • one nucleotide base is substituted for another • Example: Sickle Cell Anemia

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