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24 OKTOBER 2011

QUOTATIONIt's not that I'm so smart, it's just that I stay with problems longer. (Albert Einstein )

Factors Affecting Enzyme ActivityRates increases when amount of Enzyme increases Enzyme Activity Enzyme Concentration


Who really discovered DNA?

Fredrick Griffith Worked in the 1920s Taxonomist a scientist who classifies and names organisms He specialized in pathogens (disease-causing organisms) Used mice and bacterium (Streptococcus pneumonia) to see if inherited material is passed though DNA or protein.

Oswald Avery Continued Griffiths work Identified DNA as the material that passes on the inherited information. He used large amounts of bacteria and a process of heating and mixing the liquids to extract the nitrogen bases away from the protein Became worlds first genetic engineer

The Transforming Factor Frederick Griffith Streptococcus pneumonia bacteria was working to find cure for pneumonia


harmless live bacteria mixed with heat-killed infectious bacteria causes disease in mice substance passed from dead bacteria to live bacteria = Transforming Factor

The Transforming Factorlive pathogenic strain of bacteria A. live non-pathogenic heat-killed strain of bacteria pathogenic bacteria B. C.

mix heat-killed pathogenic & non-pathogenic bacteria D.

mice die

mice live

mice live

mice die

Transformation? something in heat-killed bacteria could still transmit disease-causing properties

DNA is the Transforming Factor Avery, McCarty & MacLeod


purified both DNA & proteins from Streptococcus pneumonia bacteria which will transform non-pathogenic bacteria?

injected protein into bacteria no effect

injected DNA into bacteria transformed harmless bacteria into virulent bacteriaWhats the conclusion?

Virus Experiments Provides More Evidence Despite Avery's findings, many scientists remained skeptical that genes were made of DNA rather than protein. Protein = 20 amino acids DNA = 4 nucleotides

Which one, DNA or protein, was truly the hereditary material? In 1952, biologists Alfred Hershey and Martha Chase provided more evidence to distinguish between these two possibilities. They conducted a series of experiments using viruses.

Hershey and Chase Experiment

A bacteriophage at work

Erwin Chargaff and his rule In 1950, biochemist Erwin Chargaff found that the arrangement of nitrogen bases in DNA varied widely, The amount of certain bases always occurred in a one-to-one ratio. Nitrogen bases always match up like this: Adenine Thymine and Cytosine -- Guanine

Rosalind Franklin (1920-1953)

Using X-ray techniques took pictures of DNA and discovered the double helix shape of DNA. Died of cancer due to unknown harmful affects of X-ray

James Watson and Francis Crick First scientists to create a model of DNA It is still the model used today Sides are made of sugar and phosphate molecules Rungs of the ladder are made of nitrogen bases Made of 5 elements: carbon, hydrogen, oxygen, nitrogen, and phosphorus

1953 Watson and Crick made a model of the DNA the Double Helix

Watson & Crick proposedDNA had specific pairing between the nitrogen bases: ADENINE THYMINE CYTOSINE - GUANINE DNA was made of 2 long stands of nucleotides arranged in a specific way called the Complementary Rule

Watson & Crick relied heavily on evidence reported by other scientists to construct their model.

X-ray photographs from Rosalind Franklin & Maurice Wilkins show that DNA is a helix with a sugarphosphate backbone on the outside and more than one chain of nucleotides

In 1962, Watson, Crick and Wilkins received the Nobel Prize in medicine for their work on DNA

Rosalind Franklin had died in 1958 from cancer (most likely caused by working with X-rays) and was not recognized

Penelitian Watson dan CrickDengan dukungan data difraksi sinar-X dari Rosalind Franklin dan Maurice Wilkins Dengan dukungan data analisis kimia basa nitrogen dari Erwin Chargaff Memformulasikan struktur DNA Mengelompokkan basa DNA menjadi purin dan pirimidin Memformulasikan model replikasi DNA






KhamirGandum Salmon Ayam

31,327,3 29,7 28,8

18,722,7 20,8 20,5

17,122,8 20,4 21,5

32,927,1 29,1 29,3

HASIL PENELITIAN CHARGAFF1. Asam nukleat yang diisolasi dari berbagai jaringan organisme yang sama memiliki komposisi basa yang sama 2. Komposisi basa Asam nukleat beragam pada organisme yang berbeda 3. Komposisi basa Asam nukleat suatu spesies tidak berubah oleh umur, nutrisi, dan lingkungan 4. Jumlah residu adenin selalu setara dengan jumlah residu timin, sedangkan jumlah residu guaninn selalu setara dengan jumlah residu sitosin

KESIMPULAN PENELITIAN CHARGAFF Asam nukleat merupakan bahan penentu sifat mahluk hidup Asam nukleat diturunkan/ditransfer dari induk ke keturunannya

Nucleic acids store information in their sequences of chemical units. Key Terms Deoxyribonucleic acid (DNA) Nucleotide Nitrogenous base Pyrimidine Purine Double helix

DNA stores the information that tells cells which proteins to make and when to use them

DNA is made up of two chains of nucleotides Double Helix

A DNA nucleotide is composed of a deoxyribose sugar molecule, a phosphate group, and a nitrogencontaining base

The four nitrogencontaining bases found in DNA molecules are adenine (A) guanine (G) cytosine (C) thymine (T)

Adenine and guanine are called purines

Cytosine and thymine are called pyrimidines

The Sugars

Cytosine pairs with guanine Adenine pairs with thymine Complementary base pairs are connected to each other by hydrogen bonds

5 vs. 3 5 end Phosphate

3 end OH-

Read from 3 to 5 Synthesized from 5 to 3


Learning Check NA1Write the complementary base sequence for the matching strand in the following DNA section:-A-G-T-C-C-A-A-T-G-C


Solution NA1Write the complementary base sequence for the matching strand in the following DNA section:-A-G-T-C-C-A-A-T-G-C -T-C-A-G-G-T-T-A-C-G-


Nucleosides in DNABase Adenine (A) Guanine (G) Cytosine (C) Thymine (T) Sugar Deoxyribose Deoxyribose Deoxyribose Deoxyribose Nucleoside Adenosine Guanosine Cytidine Thymidine


Nucleotides in DNAdAMP dGMP dCMP dTMP Deoxyadenosine monophosphate Deoxyguanosine monophosphate Deoxycytidine monophosphate Deoxythymidine monophosphate

Nucleotides and Nucleosides

DNA Stabilization--H-bonding between DNA base pair stacks

Advantages to Double Helix Stability---protects bases from attack by H2O soluble compounds and H2O itself. Provides easy mechanism for replication


Ribonucleic Acid

Like DNA, RNA is a nucleic acid made up of repeating nucleotides RNAs structure is different from DNA because it is a single-strand of nucleotides and the sugar backbone is made up of ribose Uracil replaces thymine in RNA and pairs with adenine

Forms of RNA Three forms of RNA are involved in protein synthesis mRNA tRNA rRNA

mRNA mRNA carries genetic information from the DNA in the nucleus to the cytosol of a eukaryotic cell The process of copying genetic information from DNA to mRNA is called transcription

tRNA tRNA binds to specific amino acids, helping to form polypeptide chains


rRNA makes up the ribosomes where proteins are made

QUOTATIONThe scientist is not a person who gives the right answers, he's one who asks the right questions. ~Claude Lvi-Strauss, Le Cru et le cuit, 1964


Nucleobases are ambidentate ligands, which offer several different coordination sites for metal ion. An important aspect is the ability of nucleobases to exist in different tautomeric forms.

Tautomerisasi dari uracil Keto-enol

The normal bases of DNA/RNA are usually present in the keto form. The formation of false tautomer may lead to mispairing of nucleobases, and can alter genetic information transfer (mutagenic or carcinogenic)

DNA replication is the molecular mechanism for inheritance. Key Terms DNA replication DNA polymerase

Copying DNA Replication of DNA base pairing allows each strand to serve as a template for a new strand

Alternative models so how is DNA copied?

Models of DNA Replicationconservative semiconservative dispersive

Semi-conservative replication Meselson & Stahl label parent nucleotides in DNA strands with heavy nitrogen = 15N label new nucleotides with lighter isotope = 14N


The Most Beautiful Experiment in Biologyparent replication

Make predictions

Semi-conservative replication Make predictions


15N strands replicated in 14N medium 1st round of replication? where should the bands be? 2nd round?

Template Mechanism Before a cell divides, it copies its DNA by a process called replication Replication results in two exact copies of the cells DNA

Replication begins with the separation of the DNA chains by helicase enzymes Then as DNA polymerases move along the separated chain, new chains of DNA are assembled using nucleotides in the surrounding medium

Nucleotides in DNA are grouped into genes, which contain the information required for the production of specific proteins

One gene, one polypeptide George Beadle & Edward Tatum Orange bread mold (Neurospora crassa) One gene-one enzyme h