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ASAM NUKLEAT
24 OKTOBER 2011
QUOTATION
It's not that I'm so smart, it's just that I stay with problems longer.
(Albert Einstein )
Factors Affecting Enzyme Activity
Enzyme ConcentrationEnzyme Concentration
Enz
yme
Enz
yme
Act
ivit
yA
ctiv
ity
Rates increases when amount Rates increases when amount of Enzyme increasesof Enzyme increases
SEJARAH PENEMUAN ASAM NUKLEAT
Who really discovered DNA?
Fredrick Griffith
•Worked in the 1920’s •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 Griffith’s 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 world’s first genetic engineer
The “Transforming Factor” 1928
•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 Factor”
Transformation?something in heat-killed bacteria could still transmit disease-causing properties
live pathogenicstrain of bacteria
live non-pathogenicstrain of bacteria
mice die mice live
heat-killed pathogenic bacteria
mix heat-killed pathogenic & non-pathogenicbacteria
mice live mice die
A. B. C. D.
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 bacteria
1944
What’s theconclusion?
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
1953Watson and Crick made a model of the DNA – the Double
Helix
Watson & Crick proposed…Watson & Crick proposed…•DNA had specific pairing between the DNA had specific pairing between the
nitrogen bases:nitrogen bases:
ADENINEADENINE – – THYMINETHYMINE
CYTOSINECYTOSINE - - GUANINEGUANINE
•DNA was made of DNA was made of 22 long stands of long stands of nucleotides arranged in a specific way nucleotides arranged in a specific way
called the called the “Complementary Rule”“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 sugar-phosphate 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
PenelitianPenelitianWatson dan CrickWatson dan Crick
Dengan dukungan data difraksi Dengan dukungan data difraksi sinar-X dari Rosalind Franklin sinar-X dari Rosalind Franklin dan Maurice Wilkins dan Maurice Wilkins
Dengan dukungan data analisis Dengan dukungan data analisis kimia basa nitrogen dari Erwin kimia basa nitrogen dari Erwin ChargaffChargaff
Memformulasikan struktur DNAMemformulasikan struktur DNA
Mengelompokkan basa DNA Mengelompokkan basa DNA menjadi purin dan pirimidin menjadi purin dan pirimidin
Memformulasikan model Memformulasikan model replikasi DNAreplikasi DNA
KOMPOSISI BASA PENYUSUN ASAM NUKLEAT
OrganismeOrganisme AA GG CC TT
Escherichia coliEscherichia coli 24,724,7 26,026,0 25,725,7 23,623,6
KhamirKhamir 31,331,3 18,718,7 17,117,1 32,932,9
GandumGandum 27,327,3 22,722,7 22,822,8 27,127,1
SalmonSalmon 29,729,7 20,820,8 20,420,4 29,129,1
AyamAyam 28,828,8 20,520,5 21,521,5 29,329,3
HASIL PENELITIAN CHARGAFF
1. 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 nitrogen-containing base
•The four nitrogen-containing 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’
35
Learning Check NA1
Write the complementary base sequence for the matching strand in the following DNA section:
-A-G-T-C-C-A-A-T-G-C- • • • • • • • • • • • • • • • • • • • •
36
Solution NA1
Write 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-
37
Nucleosides in DNA
Base Sugar NucleosideAdenine (A) Deoxyribose
AdenosineGuanine (G) Deoxyribose
GuanosineCytosine (C) Deoxyribose CytidineThymine (T) Deoxyribose
Thymidine
38
Nucleotides in DNA
dAMP Deoxyadenosine monophosphatedGMP Deoxyguanosine monophosphatedCMP Deoxycytidine monophosphatedTMP 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
RNA
Ribonucleic Acid
•Like DNA, RNA is a nucleic acid made up of repeating nucleotides
•RNA’s 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•rRNA makes up the ribosomes where
proteins are made
QUOTATION
The scientist is not a person who gives the right answers, he's one who asks the right questions. ~Claude Lévi-
Strauss, Le Cru et le cuit, 1964
TAUTOMERISASI DNA
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
Models of DNA Replication
• Alternative models▫so how is DNA copied?
conservative 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 Biology”
1958
parent replication
Make predictions…
Semi-conservative replication•Make predictions…
▫ 15N strands replicated in 14N medium ▫1st round of replication?▫2nd round?
1958
where should the bands be?
•Before a cell divides, it copies its DNA by a process called replication
•Replication results in two exact copies of the cell’s DNA
Template Mechanism
•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”
hypothesis
• Genes actually dictate the production of a single polypeptide (part that makes up a protein/enzyme).▫ One gene-one polypeptide
Information Flow: DNA to RNA to Protein
Triplet Code
Each codon stands for a particular amino acid.
The codon AUG not only stands for methionine (Met), but also functions as a signal to "start" translating an RNA transcript.
There are also three "stop" codons that do not code for amino acids, but signal the end of each genetic message.
1.JELASKAN BEBERAPA FUNGSI ENZIM2.JELASKAN BEBERAPA FUNGSI ASAM
NUKLEAT3.JELASKAN PERBEDAAN DNA DAN RNA4. JELASKAN 3 STRUKTUR DNA