chapter 6
DESCRIPTION
Chapter 6. Expression of Biological Information. Concepts review. Expression of Biological Information. DNA & Genetic Information. Operon. Abilities of DNA. Produce polypeptide. Forming new DNA. Gene hypothesis. DNA as genetic material. Protein synthesis. Griffith (1931). - PowerPoint PPT PresentationTRANSCRIPT
Chapter 6Expression
of Biological Information
Concepts review
Expression of Biological
Information
DNA & Genetic Information
DNA as genetic material
Gene hypothesi
s
Abilities of DNA
Forming new DNA
Produce polypeptide
ReplicationProtein
synthesis
Operon
Griffith (1931)
Avery et. al
(1944)
Beadle & Tatum (1944)
Hershey & Chase
At the end of the lesson, you At the end of the lesson, you should be able to :should be able to :
Explain DNA as the carrier of genetic information.Explain gene concept : One gene one polypeptideDescribe the semi-conservative replication of DNA
DNA as genetic material
Carrier of Carrier of genetic genetic
information information
DNA as genetic material…DNA as genetic material…Frederick Griffith (1931)
Streptococcus pneumoniae
mouse
Two types
Mutant typeRough, non-
virulent(IIR)
Wild typesmooth, virulent
(IIIS)
DNA as genetic material…DNA as genetic material…
Sample 1Frederick Griffith
(1931)
DNA as genetic material…DNA as genetic material…
Sample 2Frederick Griffith
(1931)
DNA as genetic material…DNA as genetic material…
Sample 3Frederick Griffith
(1931)
DNA as genetic material…DNA as genetic material…
Sample 4Frederick Griffith
(1931)
Living S cells found in the
blood
DNA as genetic material…DNA as genetic material…Frederick Griffith
(1931)conclusion
Living R cells are converted Living R cells are converted to S cells.to S cells.
Transformation occurred.Transformation occurred.
What is the transforming agent?
DNA as genetic material…DNA as genetic material…Concepts of transformation
Transformation is a types of genetic transfer found in bacteria.
Bacteria can take up the externally DNA.
DNA as genetic material…DNA as genetic material…
Oswald T. Avery
DNA as transforming agent
Colin MacLeod
Maclyn McCarty
DNA as genetic material…DNA as genetic material…
S strain(killed)
R strain(living)+
Protein destroye
d
RNA destroye
d
DNA destroye
d
Lipid eliminate
dLiving
S cells
Living S
cells
Living S
cells
Living R
cellsNo transformation
DNA as transforming agent
protease
RNase DNase centrifugation
DNA as genetic material…DNA as genetic material…Avery et. al (1944)
conclusionThe strain without DNA caused no transformation occur.So, the transformation agent is DNA!
DNA as genetic material…DNA as genetic material…Hershey and Chase
Prove that DNA is the molecules that responsible as genetic information, not protein.
Bacteriophages
Gene Hypothesis
One gene one One gene one polypeptidepolypeptide
Gene Hypothesis…
Edward Tatum
George Beadle
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.
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.
Gene Hypothesis…Beadle & Tatum
Experiment
Minimal Nutrient
Gene
Enzyme
Minimal Nutrient
Amino acid
Mutant neurospora
Wild type neurospora
Case 1Case2Case 3Amino acid
How to make sure ONE genes is only code ONE polypeptide???
Gene A
Gene B
Gene C
Precursor
Ornithine
Citrulline
Arginine
Enzyme A
Enzyme B
Enzyme C
+Ornithine
+Citrulline
+Arginine
X X
X X
X X
Is the gene A only produce enzyme A
only?
Is the gene B only produce enzyme B
only?
Is the gene C only produce enzyme C
only?
Gene Hypothesis…Beadle & Tatum
Experimentconclusion
Each gene will produce certain enzyme (polypeptide)
One gene one polypeptide.
DNA Replication Model
Meselson and Meselson and StahlStahl
DNA Replication Model…
Proposed by Matthew Meselson (left) and Franklin W. Stahl (right) in 1958.
DNA Replication Model…
DNA Replication
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.
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.
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?
DNA Replication Model…Meselson & Stahl
(1958)
Both parent strand remain together and
all new copies is made.
Hypothesis 1conservative
DNA Replication Model…Meselson & Stahl
(1958)
The 2 strand of the parental molecule separate and each
functions as a template for
synthesis of a new complementary
strand
Hypothesis 2semiconservative
DNA Replication Model…Meselson & Stahl
(1958)
Each strand of both daughter molecules contains a mixture of old and newly synthesized parts
Hypothesis 3dispersive
DNA Replication Model…Meselson & Stahl
(1958)
DNA Replication Model…Meselson & Stahl
(1958)
Second replication
First replication
Result
DNA Replication Model…Meselson & Stahl
(1958)
Second replication
First replication
Result
DNA Replication Model…Meselson & Stahl
(1958)
Second replication
First replication
Result
DNA Replication Model…Meselson & Stahl
(1958)
Second replicatio
n
First replicatio
n
DNA Replication Model…Meselson & Stahl
(1958)conclusion
DNA replication is take place by DNA replication is take place by semiconservative.