Warm Up:

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

11. 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

12. 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

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

14. 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

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

16. 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

17. 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

18. 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

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

20. 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

21. Helicase T A A A T U C G G C G G T A A C G G

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

23. AUG= Met (start)

24. 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

25. tRNA

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

27. 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

28. 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

29. Add one or more extra nucleotides into the DNA

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

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

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