2Students will explain classical genetics at the molecular level Summarize the historical discovery of the DNA molecular structure by Franklin, Watson and CrickDescribe how genetic information is contained in the sequence of bases in DNADescribe DNA replication
3Some History 1928 Frederick Griffith (British) Studied Streptococcus Pneumoniaepneumonia bacteriatwo genetic strainsColonies appeared smooth (S type)Surrounded by a mucous coat or capsuleColonies that appeared rough (R type)
8R BacteriaS BacteriaDead R BacteriaDead S Bacteria
9R BacteriaS BacteriaDead R BacteriaDead S Bacteria
10R BacteriaS BacteriaDead R BacteriaDead S BacteriaDead S & Live R
11R BacteriaS BacteriaDead R BacteriaDead S BacteriaDead S & Live R
12Dead R Bacteria Dead S Bacteria Dead S & Live R Capsule of S and live R
13Dead R Bacteria Dead S Bacteria Dead S & Live R Capsule of S and live R
14Dead R Bacteria Dead S Bacteria Dead S & Live R Capsule of S and live RDNA of S and live R
15Dead R Bacteria Dead S Bacteria Dead S & Live R Capsule of S and live RDNA of S and live R
16He used two strains of Streptococcus pneumoniae: In 1928, Frederick Griffith performed an experiment using pneumonia bacteria and mice. This was one of the first experiments that hinted that DNA was the genetic code material.He used two strains of Streptococcus pneumoniae:a “smooth” strain which has a polysaccharide coating around it that makes it look smooth when viewed with a microscope,a “rough” strain which doesn’t have the coating, thus looks rough under the microscope.When he injected live S strain into mice, the mice contracted pneumonia and died.When he injected live R strain, a strain which typically does not cause illness, into mice, as predicted they did not get sick, but lived.
17Thinking that perhaps the polysaccharide coating on the bacteria somehow caused the illness and knowing that polysaccharides are not affected by heat, Griffith then used heat to kill some of the S strain bacteria and injected those dead bacteria into mice.This failed to infect/kill the mice, indicating that the polysaccharide coating was not what caused the disease, but rather, something within the living cell.Since Griffith had used heat to kill the bacteria and heat denatures protein, he next hypothesized that perhaps some protein within the living cells, that was denatured by the heat, caused the disease.
18This evidence pointed to DNA as being the genetic material. He then injected another group of mice with a mixture of heat-killed S and live R, and the mice died!When he did a necropsy on the dead mice, he isolated live S strain bacteria from the corpses.Griffith concluded that the live R strain bacteria must have absorbed genetic material from the dead S strain bacteria, and since heat denatures protein, the protein in the bacterial chromosomes was not the genetic material.This evidence pointed to DNA as being the genetic material.
19Controls cellular activities of an organism by Functions of DNAControls cellular activities of an organism byCoding for structural proteinsCoding for enzymes
20Nucleic Acids DNA Deoxyribonucleic Acid Genetic material Can self-replicateMade up of NucleotidesShape = double helixA twisted rope ladderA full twist every 10 nucleotides
21DNA DiscoveryRosalind Franklin was using X-Ray Diffraction to study DNAHer work allowed Watson and Crick to come up with model of DNAFindings presented in 1953Visually confirmed in 1969
24Nucleotides Nucleotides are composed of A sugar A phosphate five carbonsDeoxyriboseA phosphatePO4-One of 4 nitrogen basesAdenine [A]Thymine [T]Cytosine [C]Guanine [G]The sugar-phosphate groups are the side rails of ladder and the the nitrogen bases are the rungs
26NucleotidesThe two strands of DNA are complimentary because the nitrogen bases bond with each other according to some rules.Adenine will only bond with ThymineGuanine will only bond with CytosineNitrogen bases bond via hydrogen bonds.These break over 70oC (denature)
30DNA REPLICATIONDNA must have the ability to create an exact duplicate of itselfThe sequence in one strand determines precisely what the sequence of nucleotides in the other strand will be. (A-T, G-C)
31DNA REPLICATIONThe hydrogen bonds holding the two complimentary strands together breakDNA strands separateFree floating complimentary nucleotides match up with nucleotides on the parent DNA strand.Catalyzed by DNA polymeraseNew, semi-conservative strands are formed
32DNA REPLICATION Semi-conservative The daughter strands are made up of one half old strand on one half new strandThe DNA unzips due to the hydrogen bonds between the bases being broken (DNA Helicase)These exposed bases attract free floating bases, which are attached to the chain by DNA polymerase.
39Students will explain classical genetics at the molecular level Describe RNA transcriptionDescribe how genetic information is translated into amino acid chains in proteinsExplain how mutations result in abnormalities or create genetic variabilityExplain how base sequences in nucleic acids give evidence for evolution
54DNA vs RNADNAOne type of DNARNAMany types of RNA
55DNA vs RNA DNA One type of DNA RNA Many types of RNA Messenger RNA (mRNA)
56DNA vs RNA DNA One type of DNA RNA Many types of RNA Messenger RNA (mRNA)Transfer RNA (tRNA)
57DNA vs RNA DNA One type of DNA RNA Many types of RNA Messenger RNA (mRNA)Transfer RNA (tRNA)Ribosomal RNA (rRNA)
58DNA vs RNA DNA One type of DNA RNA Many types of RNA Messenger RNA (mRNA)Transfer RNA (tRNA)Ribosomal RNA (rRNA)Small nuclear RNA (smRNA)
59DNA vs RNA DNA One type of DNA Mostly in nucleus RNA Many types of RNA Messenger RNA (mRNA)Transfer RNA (tRNA)Ribosomal RNA (rRNA)Small nuclear RNA (smRNA)
60DNA vs RNA DNA One type of DNA Mostly in nucleus RNA Many types of RNA Messenger RNA (mRNA)Transfer RNA (tRNA)Ribosomal RNA (rRNA)Small nuclear RNA (smRNA)Mostly found in cytoplasm
61DNA vs RNA DNA One type of DNA Mostly in nucleus Can self-replicate under the right conditionsRNAMany types of RNAMessenger RNA (mRNA)Transfer RNA (tRNA)Ribosomal RNA (rRNA)Small nuclear RNA (smRNA)Mostly found in cytoplasm
62DNA vs RNA DNA One type of DNA Mostly in nucleus Can self-replicate under the right conditionsRNAMany types of RNAMessenger RNA (mRNA)Transfer RNA (tRNA)Ribosomal RNA (rRNA)Small nuclear RNA (smRNA)Mostly found in cytoplasmCannot self-replicate
63A gene is a segment of DNA Genes and ProteinsA gene is a segment of DNACarries the information of the synthesis of a proteinOne gene codes for one protein
64Proteins in the Body Enzymes Hormones Antibodies Hemoglobin Cell membranesReceptor moleculesCarrier molecules
65Composition of Proteins Made up of 20 different amino acidsSequence of a.a.’s identifies proteinSequence of bases in DNA determines Sequence of a.a.’sOne gene = one proteinProtein Synthesis relies on 3 types of RNArRNAmRNAtRNA
66Types of RNA Ribosomal RNA (rRNA) Messenger RNA (mRNA) Makes up the ribosomesMessenger RNA (mRNA)Involved in transcription (first stage of protein synthesis)Carries message from DNA in nucleus to ribosome in cytoplasmTransfer RNA (tRNA)carries amino acids to mRNAtRNA & rRNA- In cytoplasm onlymRNAin cytoplasm & nucleusAll RNA produced in nucleolus.
671. Transcription 2. Translation Protein SynthesisOccurs primarily in ribosomesInstructions for protein contained in DNAMessage must get from nucleus to cytoplasm (DNA to ribosome)Process occurs in 2 stepswatch animations – click on the words below1. Transcription Translation
68Protein Synthesis Summary mRNA is made using DNA templatemRNA exits nucleustRNA picks up aa’stRNA anticodon bonds to mRNA codonPeptide bond forms between aa’sProtein used by cell or packaged & exportedmRNA breaks into free nucleotidestRNA’s free to pick up more aa’sTranscriptionTranslation
69Transcription mRNA made using DNA as a template In nucleusmRNA made using DNA as a templateIf the DNA base sequence isA A T T C C G G A (3 triplets)The mRNA molecule manufactured would beU U A A G G C C U (3 triplets)Each triplet is a codon
75Codons Code for amino acids May code for start (initiator codon) May code for stop (terminator codon)AUG is an initiator codon but also codes for the amino acid methioineIf code AUG is in middle it must code for methionine
76Data table of mRNA codons supplied in diploma!!Can be used to work outDNA, tRNA oramino acid sequence
93Review Questions mRNA codon for AAT DNA triplet = DNA triplet for CCG mRNA codon =tRNA anticodon for GCA DNA triplet =mRNA codon for GAU tRNA =tRNA anticodon for UUA mRNA codon =DNA triplet for CUA anticodon =codon for UAG anticodon =anticodon for CTA DNA triplet =
94Answers to Review Questions mRNA codon for AAT DNA triplet = UUADNA triplet for CCG mRNA codon = GGCtRNA anticodon for GCA DNA triplet = GCAmRNA codon for GAU tRNA = CUAtRNA anticodon for UUA mRNA codon = AAUDNA triplet for CUA anticodon = CTAcodon for UAG anticodon = AUCanticodon for CTA DNA triplet = CUA
96Mutations Changes in the sequence of bases in DNA Caused by mutagenic substances likeX-rayscosmic raysUV lightSome chemicalsMutagens can affect a single point in the DNA or it can affect large sections.Result = the proteins that the DNA codes for will be altered.
97Mutations 3 types of mutations. INSERTION DELETION SUBSTITUTION An extra nucleotide is inserted into the DNACauses a frame shiftDELETIONA nucleotide is deleted from the DNASUBSTITUTIONOne nucleotide is substituted for another
102Using DNA to explain Evolution Species that are closely related will share very similar DNA sequencesScientists use mitochondrial DNA (mtDNA) to study the relationship between speciesUsed to explain variety of ethnic groups found throughout the world (all from African descendents)
103Using SINEs and LINEsSINEs and LINEs are repeated DNA sequences that don’t code for anything, but show an evolutionary relationshipFinding a SINE or LINE in two species and not in other species, signifies that the first two species must be more closely related to each other than to the other species
104Students will explain classical genetics at the molecular level Explain DNA transformation(recombinant DNA)Describe the role of restriction enzymes and ligases in transformation
105Genetic EngineeringA desired gene can be isolated and millions of copies madeThese copies can then be analyzed to determine the gene’s nucleotide sequenceThis nucleotide sequence can be decoded to find the sequence of amino acids in the corresponding protein
106Genetic EngineeringFunctioning genes can be transferred into cells or bacteria, yeasts, plants, animalsi.e – GriffithDNA can be “made to order” using “gene machines” that can be programmed to produce short strands of DNA in any desired sequenceUseful for studying DNA,protein synthesis experimentsChange genetic code to eliminate particular amino acids from a proteinFind how the amino acid affects the protein’s function
107TransformationTransformation is the process whereby one strain of a bacterium absorbs genetic material from another strain of bacteria and “turns into” the type of bacterium whose genetic material it absorbed. Because DNA was so poorly understood, scientists remained skeptical up through the 1940s.
110Genetic Engineering Recombinant DNA To recombine DNAA technique to determine gene expressionGene segments from different sources are recombined in vitro and transferred into cells (usually E. coli) to see what happens.
111Genetic Engineering Recombinant DNA First successful GE experiment with human DNA took place in 1980Human gene which codes for the protein interferon was successfully introduced into a bacteria cell…The bacteria produced human protein.Interferon combats viral infections and may help in fighting cancer
112Genetic Engineering Recombinant DNA Genetic Engineering Recombinant DNA – How It WorksGenetic Engineering Recombinant DNAThe desired gene is isolated and cut out of the DNAA “restriction enzyme” (restriction endonuclease) does thisIsolated gene is inserted into a bacterial plasmid using a ligaseLigase is an enzyme which normally repairs breaks in the DNA backboneNew DNA now called recombinant DNA
113Genetic Engineering Recombinant DNA The plasmid is absorbed by a bacteriumReproduces asexually to produce many clones containing the recombinant DNABacterial cells produce the protein coded by the foreign geneDesired protein can be isolated and purified from the culture.
114Genetic Engineering Recombinant DNA Examples of recombinant DNA technology…InterferonHuman growth hormoneHuman insulinGene TherapyAgriculture…
118Genetic Engineering Recombinant DNA Gene TherapyReplacement of defective genes with normal healthy genese.g. Cystic fibrosis, hemophilia, sickle-cell anemia, immune-deficienciesOBSTACLES today include …How to fit genes into the body cellsHow to control the introduced genes
119Genetic Engineering Recombinant DNA AgricultureIntroduction of genes for resistance to disease, drought, frost, increased protein production, larger fruit…
120Genetic Engineering DNA Fingerprinting Used in forensic studies…Small quantities of blood, semen, or other tissue can be tested for the DNA base sequenceThe DNA nucleotide sequence is unique for every individual (except identical twins)A technology called RFLP auto-radiography is used to display selected DNA fragments as bands
121Genetic Engineering DNA Fingerprinting Radioactive probes mark the bands that contain certain markers…Only 5 or 10 regions of the entire genetic content of the cell are testedThis was a defense argument used by the O.J. Simpson lawyersThe probability of having matching DNA fingerprints is about 1 in a million.