Expression of Biological Information Chapter 6 Expression of Biological Information

Concepts review

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

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

Carrier of genetic information DNA as genetic material Carrier of genetic information

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)

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

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

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

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

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?

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.

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

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

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

One gene one polypeptide Gene Hypothesis One gene one polypeptide

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.

Beadle & Tatum Experiment Gene Hypothesis… Beadle & Tatum Experiment

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

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

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

DNA Replication Model Meselson and Stahl

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

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.

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.

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?

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.

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

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

DNA Replication Model… Meselson & Stahl (1958)

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

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

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

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

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