1. Expression of Biological Information
Chapter 6
Expression of Biological Information

2. Concepts review

3. DNA & Genetic Information DNA as genetic material
Expression of Biological Information
DNA & Genetic Information
Operon
Abilities of DNA
Produce polypeptide
Forming new DNA
DNA as genetic material
Gene hypothesis
Protein synthesis
Griffith (1931)
Beadle & Tatum (1944)
Replication
Avery et. al (1944)
Hershey & Chase

4. At the end of the lesson, you should be able to :
Explain DNA as the carrier of genetic information.
Explain gene concept : One gene one polypeptide
Describe the semi-conservative replication of DNA

5. Carrier of genetic information
DNA as genetic material
Carrier of genetic information

6. Streptococcus pneumoniae
DNA as genetic material…
Frederick Griffith (1931)
Streptococcus pneumoniae
mouse
Two types
Mutant type
Rough, non-virulent
(IIR)
Wild type
smooth, virulent
(IIIS)

7. DNA as genetic material…
Frederick Griffith (1931)
Sample 1

8. DNA as genetic material…
Frederick Griffith (1931)
Sample 2

9. DNA as genetic material…
Frederick Griffith (1931)
Sample 3

10. Living S cells found in the blood
DNA as genetic material…
Frederick Griffith (1931)
Sample 4
Living S cells found in the blood

11. What is the transforming agent?
DNA as genetic material…
Frederick Griffith (1931)
conclusion
Living R cells are converted to S cells.
Transformation occurred.
What is the transforming agent?

12. Concepts of transformation
DNA as genetic material…
Concepts of transformation
Transformation is a types of genetic transfer found in bacteria.
Bacteria can take up the externally DNA.

13. DNA as transforming agent
DNA as genetic material…
DNA as transforming agent
Oswald T. Avery
Colin MacLeod
Maclyn McCarty

14. DNA as transforming agent
DNA as genetic material…
DNA as transforming agent
S strain
(killed)
R strain
(living) +
centrifugation
protease
RNase
DNase
Protein destroyed
RNA destroyed
DNA destroyed
Lipid eliminated
Living S cells
Living S cells
Living R cells
Living S cells
No transformation

15. DNA as genetic material…
Avery et. al (1944)
conclusion
The strain without DNA caused no transformation occur.
So, the transformation agent is DNA!

16. DNA as genetic material…
Hershey and Chase
Prove that DNA is the molecules that responsible as genetic information, not protein.
Bacteriophages

17. One gene one polypeptide
Gene Hypothesis
One gene one polypeptide

18. Gene Hypothesis…
Edward Tatum
George Beadle

19. Gene Hypothesis…
George Beadle and Edward Tatum experiment: connection between genes & metabolism.
Neurospora crassa as experimental organism.
- short life-cycle, easily grown.
Since it is haploid for much of its life cycle, mutations would be immediately expressed.

20. Gene Hypothesis…
Neurospora crassa able to synthesize all of the amino acids and other chemicals needed for growth
Mutations will affect a single genes and single enzymes in specific metabolic pathways.

21. Beadle & Tatum Experiment
Gene Hypothesis…
Beadle & Tatum Experiment

23. Case2 Case 1 Case 3 Minimal Nutrient Minimal Nutrient Gene Amino acid
Enzyme
Amino acid
Wild type neurospora
Mutant neurospora
Minimal Nutrient
Minimal Nutrient

24. X X X X X X + Ornithine + Citrulline + Arginine
How to make sure ONE genes is only code ONE polypeptide???
Is the gene C only produce enzyme C only?
Is the gene B only produce enzyme B only?
Is the gene A only produce enzyme A only?
Gene A
Gene B
Gene C
Precursor X X
Enzyme A +
Ornithine
Ornithine X X
Enzyme B +
Citrulline
Citrulline X X
Enzyme C
Arginine +
Arginine

25. Beadle & Tatum Experiment
Gene Hypothesis…
Beadle & Tatum Experiment
conclusion
Each gene will produce certain enzyme (polypeptide)
One gene one polypeptide.

26. DNA Replication Model
Meselson and Stahl

27. DNA Replication Model…
Proposed by Matthew Meselson (left) and Franklin W. Stahl (right) in 1958.

28. DNA Replication Model…
Process of copying a double stranded DNA strand which is the two resulting double strands are identical and each of them consist of one original and one newly synthesize strand.

29. DNA Replication Model…
Watson and Crick suggest that each strands of DNA molecule could serve as template for the synthesis of opposite strand.
Each half-helix could pair with their complementary nucleotides to replace its missing partner.
Will result two DNA double helices, each identical to the original.

30. Studied the replication in E. coli
DNA Replication Model…
Meselson & Stahl (1958)
Studied the replication in E. coli
3 hypotheses
conservative
semiconservative
dispersive
Which one is the model of DNA replication?

31. Both parent strand remain together and all new copies is made.
DNA Replication Model…
Meselson & Stahl (1958)
Hypothesis 1
conservative
Both parent strand remain together and all new copies is made.

32. DNA Replication Model…
Meselson & Stahl (1958)
Hypothesis 2
semiconservative
The 2 strand of the parental molecule separate and each functions as a template for synthesis of a new complementary strand

33. DNA Replication Model…
Meselson & Stahl (1958)
Hypothesis 3
dispersive
Each strand of both daughter molecules contains a mixture
of old and newly synthesized parts

34. DNA Replication Model…
Meselson & Stahl (1958)

35. DNA Replication Model…
Meselson & Stahl (1958)
Result
First replication
Second replication

36. DNA Replication Model…
Meselson & Stahl (1958)
Result
First replication
Second replication

37. DNA Replication Model…
Meselson & Stahl (1958)
Result
First replication
Second replication

38. DNA Replication Model…
Meselson & Stahl (1958)
First replication
Second replication

39. DNA replication is take place by semiconservative.
DNA Replication Model…
Meselson & Stahl (1958)
conclusion
DNA replication is take place by semiconservative.