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Bio 178 Lecture 27

Bio 178 Lecture 27. Genetics and DNA. Reading. Chapters 13 & 14. ?. Quiz Material. Questions on P 276-278 & 300 Chapters 13 & 14 Quizzes on Text Website (www.mhhe.com/raven7). Outline. Genetics Human Genetics (cntd) Chromosomes and Genetics DNA

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Bio 178 Lecture 27

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  1. Bio 178 Lecture 27 Genetics and DNA

  2. Reading • Chapters 13 & 14 ? Quiz Material • Questions on P 276-278 & 300 • Chapters 13 & 14 Quizzes on Text Website (www.mhhe.com/raven7)

  3. Outline • Genetics • Human Genetics (cntd) • Chromosomes and Genetics • DNA • Experiments - DNA is hereditary material • DNA Structure • DNA Replication

  4. Nondisjunction (Cntd.) • Nondisjunction of Sex Chromosomes Generally, the effects are not as severe as nondisjunction of autosomes. 1. X Chromosome (a) Triple X Syndrome Usually taller than average females, generally “normal” and most are *fertile. (b) Klinefelter Syndrome XX + Y  XXY Sterile male with female characteristics and sometimes mildly impaired intelligence.

  5. Klinefelter Syndrome http://www.carolguze.com/text/442-4-chromosome_abnormalities.shtml Klinefelter calico cat - evidence that Y chromosome determines maleness.

  6. Nondisjunction of Sex Chromosomes (Cntd.) (c) Turner Syndrome (Monosomy X) X + O  XO Short females with edema (resulting in webbed neck) that are almost always sterile. http://www.carolguze.com/text/442-4-chromosome_abnormalities.shtml

  7. Nondisjunction of Sex Chromosomes (Cntd.) (d) OY O (egg) + Y  OY Lethal - genes on the X chromosome are necessary for survival. 2. Y Chromosome X + YY (sperm)  XYY Tall, fertile males. Genetic Counseling Read P 274.

  8. Nondisjunction

  9. Nondisjunction

  10. Nondisjunction

  11. Pedigree Example The above pedigree is for a rare kidney disease. Deduce the inheritance (autosomal, sex-linked, dominant, recessive).

  12. Exam 4 to Here!

  13. Molecular Biology

  14. Which Part of the Chromosome is Responsible for Heredity? • Scientific View up to 1940s 1. Human chromosomes are 60% protein. 2. Proteins are more heterogeneous than nucleic acids (20 amino acids compared to 2 bases).  Genetic material assumed to be protein. • Griffith (1928) Hereditary material can be passed between cells (transformation). Read P 282.

  15. Griffith’s Experiment

  16. Which Part of the Chromosome is the Genetic Material (Cntd.)? • Hershey and Chase (1952) DNA (not protein) is the hereditary material. Read P 283. Write a QHP for this experiment and hand in for extra credit.

  17. What is the Structure of DNA? • Levene (1920s) DNA is a polymer of 5-C sugar, phosphate, & 4 bases (A, T, C, G). Believed bases in equal proportions. Read P 284-285. • Chargaff (1947) - Chargaff’s Rules (a) The amounts of the 4 bases are not equal. (b) A=T and C=G

  18. What is the Structure of DNA (Cntd.)? • Franklin (1953) Method X-ray diffraction of DNA. Results (a) DNA is a double helix with a sugar-phosphate backbone. (b) Used the photographs to deduce the dimensions of DNA.

  19. Rosalind Franklin

  20. What is the Structure of DNA (Cntd.)? • Watson and Crick (1953) Method Built models to determine the structure of DNA (using Chargaff’s rules and Franklin’s data). Read Watson and Crick, 1953 and P 286-287.

  21. Structure of DNA

  22. Numbering the C Atoms in a Nucleotide

  23. http://bca.cryst.bbk.ac.uk/bca/cnews/books/Jun00.html

  24. How Does DNA Replicate? Complementarity suggested a copying mechanism. Eg. 5´-ACGTAAT-3´ pairs with 3´-TGCATTA-5´ There were 3 hypotheses: Conservative, dispersive, & semiconservative. • Meselson and Stahl (1958) The semiconservative hypothesis is correct. Read P 288-289 & predict what results would have been obtained for the other hypotheses (hand this in also).

  25. Meselson-Stahl Experiment

  26. Meselson-Stahl Results

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