2KWL Chart What I KNOW already about DNA What I WANT to know about DNA What I have LEARNED about DNA
3Learning Targets for Section 12-1 Summarize the relationship between genes and DNA?Describe the overall structure of DNA?
412–1 Research Behind DNA Griffith and Transformation In 1928, British scientist Frederick Griffith tried to determine which bacteria produced pneumonia.Griffith isolated two different strains.1. disease-causing = smooth colonies2. harmless strain = rough colonies.
5Griffith's Experiment Griffith injected mice 1. disease-causing bacteria- mice developed pneumonia and died.2. harmless strain - didn’t get sick at all
6Experiment cont.Griffith’s then mixed heat-killed, disease-causing bacteria with live, harmless ones and injected the mixture into miceMice developed pneumonia and many died.Found their lungs filled with the disease-causing bacteria
7Figure 12–2 Griffith’s Experiment Section 12-1Heat-killed, disease-causing bacteria (smooth colonies)Harmless bacteria (rough colonies)Control (no growth)Harmless bacteria (rough colonies)Heat-killed, disease-causing bacteria (smooth colonies)Disease-causing bacteria (smooth colonies)Dies of pneumoniaDies of pneumoniaLivesLivesLive, disease-causing bacteria (smooth colonies)Go to Section:
8Figure 12–2 Griffith’s Experiment Section 12-1Heat-killed, disease-causing bacteria (smooth colonies)Harmless bacteria (rough colonies)Control (no growth)Harmless bacteria (rough colonies)Heat-killed, disease-causing bacteria (smooth colonies)Disease-causing bacteria (smooth colonies)Dies of pneumoniaDies of pneumoniaLivesLivesLive, disease-causing bacteria (smooth colonies)Go to Section:
9Figure 12–2 Griffith’s Experiment Section 12-1Heat-killed, disease-causing bacteria (smooth colonies)Harmless bacteria (rough colonies)Control (no growth)Harmless bacteria (rough colonies)Heat-killed, disease-causing bacteria (smooth colonies)Disease-causing bacteria (smooth colonies)Dies of pneumoniaDies of pneumoniaLivesLivesLive, disease-causing bacteria (smooth colonies)Go to Section:
10Griffith’s Conclusion: Griffith hypothesized some factor transformed harmless cells into the heat-killed harmful cellsGriffith movie
11Avery and DNAAvery and his colleagues repeated Griffith’s experiment then:Used enzymes that destroyed proteins, lipids, carbohydrates, and other molecules, including the nucleic acid RNAWhen they destroyed the nucleic acid (DNA), transformation did not occur
12Avery’s Conclusion:Avery and other scientists discovered that DNA is the nucleic acid that stores and transmits the genetic information from one generation of an organism to the next
13The Hershey Chase Experiment Martha Chase and Alfred Hershey
14The Hershey Chase Experiment Studied viruses, nonliving particles smaller than a cell that can infect living organismsHershey and Chase reasoned that if they could determine which part of the virus—the protein coat or the DNA core—entered the infected cell, they would learn whether genes were made of protein or DNAThey grew viruses in cultures of radioactive isotopes of phosphorus-32 (32P) and sulfur-35 (35S).
15The Hershey Chase Experiment Proteins contain almost no phosphorus and DNA contains no sulfurIf 35S was found in the bacteria, it would mean that the viruses’ protein had been injected, If 32P was found in the bacteria, then it was the DNA that had been injected
16Figure 12–4 Hershey-Chase Experiment Section 12-1Bacteriophage with phosphorus-32 in DNAPhage infects bacteriumRadioactivity inside bacteriumBacteriophage with sulfur-35 in protein coatPhage infects bacteriumNo radioactivity inside bacteriumGo to Section:
17Figure 12–4 Hershey-Chase Experiment Section 12-1Bacteriophage with phosphorus-32 in DNAPhage infects bacteriumRadioactivity inside bacteriumBacteriophage with sulfur-35 in protein coatPhage infects bacteriumNo radioactivity inside bacteriumGo to Section:
18Figure 12–4 Hershey-Chase Experiment Section 12-1Bacteriophage with phosphorus-32 in DNAPhage infects bacteriumRadioactivity inside bacteriumBacteriophage with sulfur-35 in protein coatPhage infects bacteriumNo radioactivity inside bacteriumGo to Section:
19Hershey and Chase’s Conclusion: Hershey and Chase concluded that the genetic material of the bacteriophage was DNA, not protein.
21REVIEW In your science journal: List as many scientists you can rememberAnd describe their contribution to our understanding of DNA
22The Structure of DNADNA is a long molecule made up of units called nucleotidesEach nucleotide is made up of three parts:1. a 5-carbon sugar called deoxyribose,2. a phosphate group,3. and a nitrogenous (nitrogen- containing) base
23There are four kinds of nitrogenous bases in DNA Purines:Adenine: Expressed AGuanine: Expressed GPyrimidines:Thymine: Expressed TCytocine: Expressed C
24Figure 12–5 DNA Nucleotides Section 12-1PurinesPyrimidinesAdenineGuanineCytosineThyminePhosphate groupDeoxyriboseGo to Section:
25Chargaff’s RulesErwin Chargaff, an American biochemist, discovered that the percentages of guanine [G] and cytosine [C] are almost equal in any sample of DNAThe same thing is true for adenine [A] and thymine [T]Despite the fact that DNA samples from organisms obeyed this rule, neither Chargaff nor anyone else had the faintest idea why
27X-Ray EvidenceIn the early 1950s, a British scientist named Rosalind Franklin began to study DNA using a technique called X-ray diffractionThe X-shaped pattern in the image shows that the strands in DNA are twisted around each other like the coils of a spring, a shape known as a helix
29The Double Helix At the same time Francis Crick, and James Watson, were trying to understand the structure of DNA by building three-dimensional models of the moleculeIn 1953, Watson was shown a copy of Franklin’s X-ray pattern. In his book The Double Helix, Watson wrote: “The instant I saw the picture my mouth fell open and my pulse began to race.”
32Watson and Crick’s Conclusion: - DNA is a double helix in which two strands are wound around each other.- Each strand is made up of a chain of nucleotides.- The two strands are held together by hydrogen bonds between adenine and thymine and between guanine and cytosine.
34Learning Targets for Section 12.2 Summarize the events that happen in DNA replicationRelate the DNA molecule to chromosome structure.
3512–2 Chromosomes and DNA Replication DNA and ChromosomesMost prokaryotes have a single circular DNA molecule that contains nearly all of the cell’s genetic information
36Prokaryotic Chromosome Structure Section 12-2ChromosomeE. coli bacteriumBases on the chromosomeGo to Section:
37Differences between Prokaryotes and Eukaryotes Eukaryotic DNA is a bit more complicated. Many eukaryotes have as much as 1000 times the amount of DNA as prokaryotesDNA Length DNA molecules are surprisingly longThe chromosome of the prokaryote E. coli, contains 4,639,221 base pairs
39Length of DNAThis means that the nucleus of a human cell contains more than 1 meter of DNAHow can so much DNA be packed into each and every cell in our body?
40 Chromosome StructureEukaryotic chromosomes contain both DNA and protein, tightly packed together to form a substance called chromatinChromatin consists of DNA that is tightly coiled around proteins called histones
41 Chromosome StructureTogether, the DNA and histone molecules form a beadlike structure called a nucleosomeThis allows the chromosomes to be very tightly coiled up in the nucleus
42Figure 12-10 Chromosome Structure of Eukaryotes Section 12-2ChromosomeNucleosomeDNAdoublehelixCoilsSupercoilsHistonesGo to Section:
44DNA ReplicationWhen Watson and Crick discovered the double helix structure of DNA, there was one more remarkable aspect that they recognized immediately.The structure explained how DNA could be copied, or replicatedEach strand of the DNA double helix has all the information needed to reconstruct the other half by the mechanism of base pairing
46DNA Replication During DNA replication, the DNA molecule separates into two strandsThen produces two new complementary strands following the rules of base pairing.Each strand of the double helix of DNA serves as a template, or model, for the new strand
47Figure 12–11 DNA Replication Section 12-2Original strandNew strandDNA polymeraseGrowthDNA polymeraseGrowthReplication forkReplication forkNitrogenous basesNew strandOriginal strandGo to Section:
48DNA Replication DNA replication animationDNA Replication animation
49How DNA Replicates Start with a double strand of DNA DNA replication is carried out by a series of enzymes. which “unzip” a molecule of DNA
50How DNA Replicates A – T G – C C – G T – A I’ve deleted the sugar-phosphate backbone for easier drawingsHydrogen bonds
51DNA Unzips A – T A - T G – C G - C A – T A T C – G DNA C G T – A unzips T AC – G C G
52A – T G – C DNA PolymeraseIII A T C G T A C G DNAP III moves along each strand adding a base pair at a time
53A – TG – CA T TC G GT T AC CGDNAP III continues to moves along each strand adding a base pair at a time
54"Replication Fork"A – TG – CA T A TC G C GT A TAC G CG
55Finally get 2 new strands, exact copies AT ATGC GCCG CGTA TA
56STOP: Practice Replicate the following strand of DNA ATG GGA CCG TAT ACG GAGTAC CCT GGC ATA TGC CTC
57DNA and EnzymesDNA replication involves a host of enzymes and regulatory moleculesThe principal enzyme involved in DNA replication is called DNA polymeraseIn addition to replication DNA polymerase also “proofreads” each new DNA strand, helping to maximize the odds that each molecule is a perfect copy of the original DNA
58Learning Targets for Section 12.3 What are the three main types of RNA?What is transcription?What is translation?
5912–3 RNA and Protein Synthesis The double helix structure explains how DNA can be replicated but it does not explain how a gene worksGenes are coded DNA instructions that control the production of proteins
61RNAThe first step is to copy part of the nucleotide sequence from DNA into RNA a process called transcriptionRNA molecules then carry out the process of making proteins.RNA molecule is a working copy of a single gene.Using RNA makes it possible for a single gene to produce hundreds or even thousands of RNA molecules
62The Structure of RNAThere are three main differences between RNA and DNA:The sugar in RNA is ribose instead of deoxyriboseRNA is generally single-strandedRNA contains uracil in place of thymine
63Types of RNAThere are three main types of RNA: messenger RNA, ribosomal RNA, and transfer RNA.messenger RNA (mRNA) serves as “messengers” from DNA to the rest of the cell.ribosomal RNA (rRNA) is the site where Proteins are assembled on ribosomestransfer RNA (tRNA) transfers each amino acid to the ribosome during the construction of a protein.
64TranscriptionDuring transcription, RNA polymerase binds to DNA and separates the DNA strands.RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA
65Figure 12–14 Transcription Section 12-3Adenine (DNA and RNA)Cystosine (DNA and RNA)Guanine(DNA and RNA)Thymine (DNA only)Uracil (RNA only)RNA polymeraseDNARNAGo to Section:
67Practice Transcribing Remember A goes with T, C goes with G and Uracil takes the place of ThymineTAC GCA CCA TAT CCG ATTAUG CGU GGU AUA GGC UAA
68Where to Begin?The enzyme will bind only to regions of DNA known as promoters, which have specific base sequences.Promoters are signals in DNA that indicate to the enzyme where to bind to make RNASimilar signals in DNA cause transcription to stop when the new RNA molecule is completed
69Editing RNAMany RNA molecules have sections, called introns, edited out of them before they become functional.The remaining pieces, called exons, are spliced together.Then, a cap and tail are added to form the final RNA molecule.
71The Genetic CodeThe “language” of mRNA instructions is called the genetic code.RNA contains four different bases: A, U, C, and G.In effect, the code is written in a language that has only four “letters.”
72STOP THINK! What is the process of transcription making? Where does transcription take place?What enzymes are used to complete transcription?Compare and Contrast DNA and RNA?
73Genetic Code The genetic code is read three letters at a time Each three-letter “word” in mRNA is known as a codonA codon consists of three consecutive nucleotides that specify a single amino acid that is to be added to the polypeptide
74Genetic CodeBecause there are four different bases, there are 64 possible three-base codons (4 × 4 × 4 = 64).The codon, AUG, that can either specify methionine or serve as the initiation, or “start,” codon for protein synthesisThere are three “stop” codons that do not code for any amino acid
76TranslationDuring translation, the cell uses information from messenger RNA to produce proteinsThis process is known as translation
77TranslationBefore translation can occur, messenger RNA must first be transcribed from DNA in the nucleus and released into the cytoplasmTranslation begins when an mRNA molecule in the cytoplasm attaches to a ribosome
78Figure 12–18 Translation Section 12-3 mRNA Go to Section: Nucleus Messenger RNAMessenger RNA is transcribed in the nucleus.mRNALysinePhenylalaninetRNATransfer RNAThe mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon.MethionineRibosomemRNAStart codonGo to Section:
79TranslationAs each codon of the mRNA molecule moves through the ribosome, the proper amino acid is brought into the ribosome and attached to the growing polypeptide chainThat job is done by transfer RNA
80TranslationThe codon matches up with complementary bases on the tRNA to tell it which amino acid to bring inThe three bases on the tRNA molecule, called the anticodon, are complementary to one of the mRNA codons
81TranslationThe polypeptide chain continues to grow until the ribosome reaches a stop codon on the mRNA moleculeAt that point the protein is released to be modified in the Golgi apparatus or to be shipped out to perform its function
82Figure 12–18 Translation (continued) Section 12-3The Polypeptide “Assembly Line”The ribosome joins the two amino acids—methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids.Growing polypeptide chainRibosometRNALysinetRNAmRNACompleting the PolypeptideThe process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain.mRNATranslation directionRibosomeGo to Section:
83Practice Translating original DNA ATG CCC AGT TCA TAA Compl DNA = ___ ___ ____ ___ ____mRNA = ____ ___ ____ ____ ____Amino acid ______________, _______________, _____________, ______________, _____________.
84Check these answers first original DNA ATG CCC AGT TCA TAACompl DNA = TAC GGG TCA AGT ATTmRNA = AUG CCC AGU UCA UAA
88BELLRINGER 11/11/09 COMPARE/CONTRAST RNA TO DNA *** Include as much information about each that you can think ofTHEN DESCRIBE what happens during TRANSCRIPTIONAnd DESCRIBE WHAT HAPPENS DURING TRANSLATION
8912.4 Learning TargetsDescribe how gene mutations and chromosomal mutations occurUnderstand the difference between point mutations and frameshift mutations
90Ways variations can arise What is a mutation and where can it occur? Inheritable change in genetic code* 99.9 % are harmful. Only 0.1% are helpful!!What is a chromosomal mutation?Changes in number or structure of chromosomeWhen do chromosomal mutations occur?During Meiosis – A cell division that produces gametes
91TYPES OF MUTATIONS What is a frameshift mutation? Change that shifts the genetic message through inserting or deleting a nucleotideWhat is a point mutation?Change at one point of a chromosome.
92What is a deletion mutation? Loss of one or more genesWhat is a duplication mutation?One or more genes are copied twiceWhat is an inversion mutation?Part of a chromosome gets turned the wrong way