1. Humans are 99.9% genetically identical
HUMAN GENOME
Seq. 3 billion base pairs
About 21,000 genes
About 19,000 pseudogenes
Telomeres and repeats
Humans are 99.9% genetically identical

2. 2 % coding
24% introns
Non-coding (outside gene) is 15%
Repeats 59%

3. SIZE DOESN’T ALWAYS MATTER
Ferns – 100’s of chromosomes
Soya – 2x’s number of genes

4. SIMILARITIES
98% identical to chimps
Less similar to mice, but still same types of genes
500 genes are universal!

5. DNA AS THE CARRIER OF HEREDITARY INFORMATION AND DNA STRUCTURE

6. GRIFFITH’S TRANSFORMATION
Proved that R Pneumococcus cells (normally safe) could be transformed into pathogenic cells by a chemical when exposed to dead S cells (which were pathogenic)

9. WHAT WAS THE CHEMICAL?
Avery, McCleod, McCarty – 1944: Isolated lipids, proteins, polysaccharides, DNA and RNA from S strain and tested for transforming principle  found that DNA induced transformation

10. Hershey and Chase – 1952 : Bacteriophages labeled with radioactive P or S and left to attack bacteria. Found that P labeled components were incorporated into the cells….recall the P is found in DNA but not protein!

16. Structure suggests function

17. FRANKLIN / WILKINS
Using X ray crystallography the spatial arrangement of DNA was deduced. Pictures clearly showed a helical formation with dimensions of 0.34 nm, 3.4 nm and 2.0 nm showing up in the film.

19. ERWIN CHARGAFF
1949: Examining the relationship between bases of different organisms, he found that the ratio of purines to pyrmidines and adenine to thymine and of guanine to cytosine was 1:1  Chargaff’s rule  indicates complimentary base pairing.

22. PYRIMIDINES

23. PURINES

24. A - T

25. G - C

26. Watson and Crick used Franklin/Wilkins information to deduce structure of DNA.
- suggested that DNA is a double helix
- two polynucleotide chains
- bases were 0.34 nm apart
- 10 bases represent a full turn of the helix  hence 3.4 nm

27. - width of helix is 2.0 nm
- antiparallel strands
- fits Chargaff’s rule since a purine is 1.2 nm wide and a pyrmidine is 0.8 nm wide then 1 purine and 1 pyrimidine provide 2.0 nm in width!

29. Table 11-1 Page 221

30. Mechanisms for insuring accuracy/ transmission to next generations
DNA REPLICATION
Mechanisms for insuring accuracy/ transmission to next generations
Mechanisms for allowing change & transmission

31. Structure and complimentary base pairing suggest method of replication

33. Meselson-Stahl EXPT
Original DNA of Heavy N15
Replicated in N14  N15-N14 hybrid
N15-N14 hybrid replicated again  N15-N14 and N14-N14
Centrifuged  yielded 3 density bands

34. SEMI-CONSERVATIVE REP.

35. MUTATIONS
Changes in DNA sequence can be perpetuated if it occurs in the germ line

37. Nucleotides contain 3 phosphate groups
ENDERGONIC
Nucleotides contain 3 phosphate groups
Removal of two provides energy for polymerization

41. Replication forks expand away from initiation site 1 in prokaryotes
INITIATION SITES
Replication bubbles
Replication forks expand away from initiation site
1 in prokaryotes
Many in eukaryotes

44. Initiating Replication
Helicase unravels DNA after H bonds are broken.
ATP hydrolysis – 3 states below interconvert creating conformational changes
Conformational changes create oscillations  scissor analogy

56. SSBPs – Single stranded binding proteins prevent annealing of DNA

58. Biophysics Seminar - 09/24/ :30pm Smith Lab Mechanism of DNA Polymerization Catalyzed by Sulfolobus solfataricus P2 DNA Polymerase IV Zucai Suo, The Ohio State University, Department of Biochemistry
Like replicative DNA polymerases, Dpo4 utilizes an "induced-fit" mechanism to select correct incoming nucleotides.
What does this mean?

60. Primase lays down a primer of RNA nucleotides (5-14)
THE PRIMER
Primase lays down a primer of RNA nucleotides (5-14)
Polymerase builds off the 3’ end

62. Leading Strand – towards replication fork (continous rep.)
Lagging strand away from fork (discontinous)

63. Fragments linked by LIGASE
OKAZAKI FRAGMENTS
Primers removed
Fragments linked by LIGASE

65. DNA pol I & III can act as exonucleases (they can cut out incorrect DNA nucleotides and replace them with correct ones…reduces the rate of mutation to 1/1,000,000,000 base pairs!)

69. Telomeres
5’ ends can’t be replaced on daughter strands
DNA polymerase can’t add to the 5’ end
DNA shrinks with each round of replication
Regulates # of replications

70. Credit: © Dr. K.G. Murti/Visuals Unlimited
203283
Telomeres (yellow) at the end of human chromosomes.

71. Telomerase
Telomerase replaced telomeres
Generates immortality in cell line
Ie cancers, unicellular eukaryotes

72. All somatic cells contain same DNA
NUCLEAR EQUIVALENCE
All somatic cells contain same DNA
Specialized cells use different genes  others are deactivated

73. Other changes….
Gene Amplification  copying of genes to meet demands of organisms ie chorion gene in drosophila

75. Genomic Rearrangement
Cells rearrange genes during development to produce variety
ie 200 million types of antibody from a few genes

76. How is DNA replication regulated? HINT: When does REPLICATION occur?
REGULATION
How is DNA replication regulated?
HINT: When does REPLICATION occur?