Chapter 6 Expression of Biological Information. Concepts review.

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 polypeptide

Describe 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)


Sample 1



Sample 2



Sample 3



Sample 4


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?


Concepts of transformation

Transformation is a types of genetic transfer found in bacteria.

Bacteria can take up the externally DNA.


Oswald T. Avery

DNA as transforming agent

Colin MacLeod

Maclyn McCarty


S strain(killed)

R strain(living)+

Protein destroye

d

RNA destroye

d

DNA destroye

d

Lipid eliminate

d

Living 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)

conclusion

The 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 NutrientMinimal Nutrient

Gene

Gene

EnzymeEnzyme

Minimal NutrientMinimal Nutrient

Amino acidAmino acid

Mutant neurospora

Wild type neurospora

Case 1Case2Case 3

Amino acidAmino acid

How to make sure ONE genes is only code ONE polypeptide???

Gene A

Gene B

Gene C

Gene A

Gene B

Gene C

Precursor

Ornithine

Citrulline

Arginine

Enzyme AEnzyme A

Enzyme BEnzyme B

Enzyme CEnzyme 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

Experiment

conclusion

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

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.


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?


(1958)

Both parent strand remain together and

all new copies is made.

Hypothesis 1conservative


(1958)

The 2 strand of the parental molecule separate and each

functions as a template for

synthesis of a new complementary

strand

Hypothesis 2semiconservative


(1958)

Each strand of both daughter molecules contains a mixture of old and newly synthesized parts

Hypothesis 3dispersive


(1958)


(1958)

Second replication

First replication

Result


(1958)

Second replicatio

n

First replicatio

n


(1958)

conclusion

DNA replication is take place by DNA replication is take place by

semiconservative.

Chapter 6 Expression of Biological Information. Concepts review.

Documents

Transcript of Chapter 6 Expression of Biological Information. Concepts review.