2Chapter 12 Molecular Genetics Section 1: DNA: The Genetic MaterialSection 2: Replication of DNASection 3: DNA, RNA, and ProteinSection 4: Gene Regulation and Mutation
3Chapter 12Molecular Genetics12.1 DNA: The Genetic MaterialGriffithPerformed the first major experiment that led to the discovery of DNA as the genetic material
4DNA is the genetic material The First demonstration of bacterial transformation.Experiments done by Frederick Griffith (in London) in 1928 found there were two different types of the bacterium Streptococcus pneumoniae:An "S" or SMOOTH coat strain, which is lethal to mice.An "R" or ROUGH strain, which will not hurt the mouse.Griffith found that he could heat inactivate the smooth strain.
5Fredrick GriffithHowever, if he were to take a mixture of the heat-inactivated S strain, mixed with the R strain, the mouse would die. Thus there was some material in the heat-killed S strain that was responsible for "transforming" the R strain into a lethal form.Fred Griffith (and a lab co-worker) was killed in their laboratory in 1940 from a German bomb.
6Griffith’s work continued in U.S. in 1944, Oswald Avery, C.M. MacLeod, and M. McCarty carefully demonstrated that the ONLY material that was responsible for the transformation was DNAThus, DNA was the "Genetic material" - however, many scientists were still not sure that it was REALLY DNA (and not proteins) that was the genetic material.
7Concluded that when the S cells were killed, DNA was released Chapter 12Molecular Genetics12.1 DNA: The Genetic MaterialOswald AveryIdentified the molecule that transformed the R strain of bacteria into the S strainConcluded that when the S cells were killed, DNA was releasedR bacteria incorporated this DNA into their cells and changed into S cells.
8Used radioactive labeling to trace the DNA (P) and protein (S) Chapter 12Molecular Genetics12.1 DNA: The Genetic MaterialHershey and Chase (1952)Used radioactive labeling to trace the DNA (P) and protein (S)Concluded that the viral DNA was injected into the cell and provided the genetic information needed to produce new viruses
1012.1 DNA: The Genetic Material Chapter 12Molecular Genetics12.1 DNA: The Genetic MaterialDNA StructureNucleotidesConsist of a five-carbon sugar, a phosphate group, and a nitrogenous base
11Chargaff’s rule: C = G and T = A Chapter 12Molecular Genetics12.1 DNA: The Genetic MaterialChargaff’s rule: C = G and T = APyrimidines =Cytosine and ThyminePurines =Guanine and AdenineIn 1950, Erwin Chargaff analyzed the base composition of DNA composition in a number of organisms.He reported that DNA composition varies from one species to another. Such evidence of molecular diversity, which had been presumed absent from DNA, made DNA a more credible candidate for the genetic material than protein.
12X-ray Diffraction Structure Analysis (1951-1952) Chapter 12Molecular Genetics12.1 DNA: The Genetic MaterialX-ray Diffraction Structure Analysis ( )X-ray diffraction data helped solve the structure of DNAIndicated that DNA was a double helixThis is the famous RosalindFranklin - Picture 51 which was leaked to James Watson and FrancisCrick by Maurice Wilkins.Sodium deoxyribose nucleate from calf thymus, Structure B, Photo 51, taken by Rosalind E. Franklin and R.G. Gosling (her student). Linus Pauling's holographic annotations are to the right of the photo. May 2, 1952
13X-ray Diffraction Rosalind Franklin (1920 - 1958) Chapter 12Molecular Genetics12.1 DNA: The Genetic MaterialX-ray Diffraction Rosalind Franklin ( )The technique with which Maurice Wilkins and Franklin set out to do this is called X-ray crystallography.With this technique a crystal is exposed to x-rays in order to produce a diffraction pattern.If the crystal is pure enough and the diffraction pattern is acquired very carefully, it is possible to reconstruct the positions of the atoms in the molecules that comprise the basic unit of the crystal.Rosalind Franklin died from cancer in April of 1958, at the age of 37.
14two outside strands consist of alternating deoxyribose and phosphate Chapter 12Molecular Genetics12.1 DNA: The Genetic MaterialWatson and Crick 1953Built a model of the double helix that conformed to the others’ researchtwo outside strands consist of alternatingdeoxyribose and phosphatecytosine and guanine bases pair to eachother by three hydrogen bondsthymine and adenine bases pair to eachother by two hydrogen bonds
15Nobel Prize in Medicine/Physiology The rules of the Nobel Prize forbid posthumous nominations; because Rosalind Franklin had died in 1958 she was not eligible for nomination to the Nobel Prize subsequently awarded to Crick, Watson, and Wilkins in 1962.The award was for their body of work on nucleic acids and not exclusively for the discovery of the structure of DNA.By the time of the award Wilkins had been working on the structure of DNA for over 10 years, and had done much to confirm the Crick-Watson model. Crick had been working on the genetic code at Cambridge and Watson had worked on RNA for some years.
16DNA Structure – Double Helix Chapter 12Molecular Genetics12.1 DNA: The Genetic MaterialDNA Structure – Double HelixDNA often is compared to a twisted ladder.Rails of the ladder are represented by the alternating deoxyribose and phosphate.The pairs of bases (cytosine–guanine or thymine–adenine) form the steps.
1712.1 DNA: The Genetic Material Chapter 12Molecular Genetics12.1 DNA: The Genetic MaterialOrientationOn the top rail, the strand is said to be oriented 5′ to 3′.The strand on the bottom runs in the opposite direction and is oriented 3′ to 5′.
1812.1 DNA: The Genetic Material Chapter 12Molecular Genetics12.1 DNA: The Genetic MaterialChromosome StructureDNA coils around histones to form nucleosomes, which coil to form chromatin fibers.The chromatin fibers supercoil to form chromosomes that are visible in the metaphase stage of mitosis.
19Semiconservative Replication Chapter 12Molecular Genetics12.2 Replication of DNASemiconservative ReplicationParental strands of DNA separate, serve as templates, and produce DNA molecules that have one strand of parental DNA andone strand of new DNA.
20Chapter 12Molecular Genetics12.2 Replication of DNAUnwindingDNA helicase, an enzyme, is responsible for unwinding and unzipping the double helix.RNA primase adds a short segment of RNA, called an RNA primer, on each DNA strand. Keeping the DNA strands separate.
21Chapter 12Molecular Genetics12.2 Replication of DNABase pairingDNA polymerase (an enzyme) continues adding appropriate nucleotides to the chain by adding to the 3′ end of the new DNA strand.
23Chapter 12Molecular Genetics12.2 Replication of DNAOne strand is called the leading strand and is elongated as the DNA unwinds so is said to be synthesized continuously.The other strand of DNA, called the lagging strand, elongates away from the replication fork.The lagging strand is synthesized discontinuously into small segments, called Okazaki fragments.
24DNA ligase links the two sections. Chapter 12Molecular Genetics12.2 Replication of DNAJoiningDNA polymerase removes the RNA primer and fills in the place with DNA nucleotides.DNA ligase links the two sections.
25Comparing DNA Replication in Eukaryotes and Prokaryotes Chapter 12Molecular Genetics12.2 Replication of DNAComparing DNA Replication in Eukaryotes and ProkaryotesEukaryotic DNA unwinds in multiple areas as DNA is replicated.In prokaryotes, the circular DNA strand is opened at one origin of replication.
26Central Dogma: DNA to RNA to Protein Chapter 12Molecular Genetics12.3 DNA, RNA, and ProteinCentral Dogma: DNA to RNA to ProteinRNAContains the sugar ribose (instead of deoxyribose) and the base uracil (instead of thymine)Usually is single stranded
27Associates with proteins to form ribosomes in the cytoplasm Chapter 12Molecular Genetics12.3 DNA, RNA, and ProteinMessenger RNA (mRNA)Long strands of RNA nucleotides that are formed complementary to one strand of DNARibosomal RNA (rRNA)Associates with proteins to form ribosomes in the cytoplasmTransfer RNA (tRNA)Smaller segments of RNA nucleotides that transport amino acids to the ribosome where proteins are made by adding 1 a.a. at a time
28Chapter 12Molecular Genetics12.3 DNA, RNA, and Protein
30DNA is unzipped in the nucleus and RNA Chapter 12Molecular Genetics12.3 DNA, RNA, and ProteinTranscriptionThrough transcription, the DNA code is transferred to mRNA in the nucleus.DNA is unzipped in the nucleus and RNApolymerase binds to a specific section where anmRNA will be synthesized.
32Intervening sequences are called introns. Chapter 12Molecular Genetics12.3 DNA, RNA, and ProteinRNA ProcessingThe code on the DNA is interrupted periodically by sequences that are not in the final mRNA – introns removed..Intervening sequences are called introns.Remaining pieces of DNA that serve as the coding sequences are called exons.DNA and Genes
33The three-base code in DNA or mRNA is called a codon. Chapter 12Molecular Genetics12.3 DNA, RNA, and ProteinThe CodeExperiments during the 1960s demonstrated that the DNA code was a three-base code.The three-base code in DNA or mRNA is called a codon.
34Each anticodon is complementary to a codon on the mRNA. Chapter 12Molecular Genetics12.3 DNA, RNA, and ProteinTranslationIn translation, tRNA molecules act as the interpreters of the mRNA codon sequence.At the middle of the folded strand, there is a three-base coding sequence called the anticodon.Each anticodon is complementary to a codon on the mRNA.
3512.3 DNA, RNA, and Protein Chapter 12 Molecular Genetics Visualizing Transcriptionand Translation
36Chapter 12Molecular Genetics12.3 DNA, RNA, and ProteinOne Gene—One EnzymeThe Beadle and Tatum experiment showed that one gene codes for one enzyme. We now know that one gene codes for one polypeptide.DNA from the Beginning
37Prokaryote Gene Regulation Chapter 12Molecular Genetics12.4 Gene Regulation and MutationProkaryote Gene RegulationAbility of an organism to control which genes are transcribed in response to the environmentAn operon is a section of DNA that contains the genes for the proteins needed for a specific metabolic pathway.OperatorPromoterRegulatory geneGenes coding for proteins
38The Trp Operon 12.4 Gene Regulation and Mutation Chapter 12 Molecular Genetics12.4 Gene Regulation and MutationThe Trp Operon
39The Lac Operon 12.4 Gene Regulation and Mutation Chapter 12 Molecular Genetics12.4 Gene Regulation and MutationThe Lac OperonLac-Trp Operon
40Eukaryote Gene Regulation Chapter 12Molecular Genetics12.4 Gene Regulation and MutationEukaryote Gene RegulationControlling transcriptionTranscription factors ensure that a gene is used at the right time and that proteins are made in the right amountsThe complex structure of eukaryotic DNA also regulates transcription.
41Chapter 12Molecular Genetics12.4 Gene Regulation and MutationHox GenesHox genes are responsible for the general body pattern of most animals.
42RNA interference can stop the mRNA from translating its message. Chapter 12Molecular Genetics12.4 Gene Regulation and MutationRNA InterferenceRNA interference can stop the mRNA from translating its message.
43A permanent change that occurs in a cell’s DNA is called a mutation. Chapter 12Molecular Genetics12.4 Gene Regulation and MutationMutationsA permanent change that occurs in a cell’s DNA is called a mutation.Types of mutationsPoint mutationInsertionDeletion
4412.4 Gene Regulation and Mutation Chapter 12Molecular Genetics12.4 Gene Regulation and Mutation
45Protein Folding and Stability Chapter 12Molecular Genetics12.4 Gene Regulation and MutationProtein Folding and StabilitySubstitutions also can lead to genetic disorders.Can change both the folding and stability of the protein
46Can occur spontaneously Chapter 12Molecular Genetics12.4 Gene Regulation and MutationCauses of MutationCan occur spontaneouslyChemicals and radiation also can damage DNA.High-energy forms of radiation, such as X rays and gamma rays, are highly mutagenic.
47Body-cell v. Sex-cell Mutation Chapter 12Molecular Genetics12.4 Gene Regulation and MutationBody-cell v. Sex-cell MutationSomatic cell mutations are not passed on to the next generation.Mutations that occur in sex cells are passed on to the organism’s offspring and will be present in every cell of the offspring.
48Chapter Resource Menu Chapter Diagnostic Questions Molecular GeneticsChapter Resource MenuChapter Diagnostic QuestionsFormative Test QuestionsChapter Assessment QuestionsStandardized Test Practicebiologygmh.comGlencoe Biology TransparenciesImage BankVocabularyAnimationClick on a hyperlink to view the corresponding lesson.
49Which scientist(s) definitively proved Chapter 12Molecular GeneticsChapter Diagnostic QuestionsWhich scientist(s) definitively provedthat DNA transfers genetic material?Watson and CrickMendelHershey and ChaseAvery
50Name the small segments of the lagging DNA strand. Chapter 12Molecular GeneticsChapter Diagnostic QuestionsName the small segments of the laggingDNA strand.ligaseOkazaki fragmentspolymerasehelicase
51It contains the sugar deoxyribose. It contains the base uracil. Chapter 12Molecular GeneticsChapter Diagnostic QuestionsWhich is not true of RNA?It contains the sugar deoxyribose.It contains the base uracil.It is single-stranded.It contains a phosphate.
52The experiments of Avery, Hershey and Chapter 12Molecular Genetics12.1 Formative QuestionsThe experiments of Avery, Hershey andChase provided evidence that the carrierof genetic information is _______.carbohydrateDNAlipidprotein
53What is the base-pairing rule for purines Chapter 12Molecular Genetics12.1 Formative QuestionsWhat is the base-pairing rule for purinesand pyrimidines in the DNA molecule?A—G and C—TA—T and C—GC—A and G—TC—U and A—G
54What are chromosomes composed of? Chapter 12Molecular Genetics12.1 Formative QuestionsWhat are chromosomes composed of?chromatin and histonesDNA and proteinDNA and lipidsprotein and centromeres
55The work of Watson and Crick solved the mystery of how DNA works as a Chapter 12Molecular Genetics12.2 Formative QuestionsTrue or FalseThe work of Watson and Crick solvedthe mystery of how DNA works as agenetic code.
56Which is not an enzyme involved in DNA replication? Chapter 12Molecular Genetics12.2 Formative QuestionsWhich is not an enzyme involved in DNAreplication?DNA ligaseDNA polymeraseHelicaseRNA primer
57During DNA replication, what nucleotide Chapter 12Molecular Genetics12.2 Formative QuestionsDuring DNA replication, what nucleotidebase sequence is synthesized along anoriginal strand that has the sequenceTCAAGC?AGTTCGATGGCGCTGGATGACCTA
58Which shows the basic chain of events Chapter 12Molecular Genetics12.3 Formative QuestionsWhich shows the basic chain of eventsin all organisms for reading and expressinggenes?DNA RNA proteinRNA DNA proteinmRNA rRNA tRNARNA processing transcriptiontranslation
59In the RNA molecule, uracil replaces _______. Chapter 12Molecular Genetics12.3 Formative QuestionsIn the RNA molecule, uracil replaces_______.adeninecytosinepurinethymine
61What characteristic of the mRNA molecule Chapter 12Molecular Genetics12.3 Formative QuestionsWhat characteristic of the mRNA moleculedo scientists not yet understand?
62intervening sequences in the mRNA molecule Chapter 12Molecular Genetics12.3 Formative Questionsintervening sequences in the mRNA moleculecalled intronsthe original mRNA made in the nucleus calledthe pre-mRNAhow the sequence of bases in the mRNAmolecule codes for amino acidsthe function of many adenine nucleotidesat the 5′ end called the poly-A tail
63Why do eukaryotic cells need a complex Chapter 12Molecular Genetics12.4 Formative QuestionsWhy do eukaryotic cells need a complexcontrol system to regulate the expressionof genes?
64All of an organism’s cells transcribe the same Chapter 12Molecular Genetics12.4 Formative QuestionsAll of an organism’s cells transcribe the samegenes.Expression of incorrect genes can lead tomutations.Certain genes are expressed more frequentlythan others are.Different genes are expressed at differenttimes in an organism’s lifetime.
65Which type of gene causes cells to become specialized in structure in Chapter 12Molecular Genetics12.4 Formative QuestionsWhich type of gene causes cells tobecome specialized in structure infunction?exonHox geneintronoperon
66What is an immediate result of a mutation in a gene? Chapter 12Molecular Genetics12.4 Formative QuestionsWhat is an immediate result of a mutationin a gene?cancergenetic disordernonfunctional enzymeamino acid deficiency
67Which is the most highly mutagenic? Chapter 12Molecular Genetics12.4 Formative QuestionsWhich is the most highly mutagenic?chemicals in foodcigarette smokeultraviolet radiationX rays
68Look at the following figure. Identify the Chapter 12Molecular GeneticsChapter Assessment QuestionsLook at the following figure. Identify theproteins that DNA first coils around.
70Explain how Hox genes affect an organism. Chapter 12Molecular GeneticsChapter Assessment QuestionsExplain how Hox genes affect an organism.They determine size.They determine body plan.They determine sex.They determine numberof body segments.
71Explain the difference between body-cell and sex-cell mutation. Chapter 12Molecular GeneticsChapter Assessment QuestionsExplain the difference between body-celland sex-cell mutation.
72Answer: A mutagen in a body cell becomes part of the genetic sequence Chapter 12Molecular GeneticsChapter Assessment QuestionsAnswer: A mutagen in a body cell becomespart of the genetic sequencein that cell and in future daughtercells. The cell may die or simply notperform its normal function. Thesemutations are not passed on to thenext generation. When mutationsoccur in sex cells, they will bepresent in every cell of the offspring.
73What does this diagram show about the replication of DNA Chapter 12Molecular GeneticsStandardized Test PracticeWhat does thisdiagram show aboutthe replication of DNAin eukaryotic cells?
74DNA is replicated only at certain places along Chapter 12Molecular GeneticsStandardized Test PracticeDNA is replicated only at certain places alongthe chromosome.DNA replication is both semicontinuous andconservative.Multiple areas of replication occur along thechromosome at the same time.The leading DNA strand is synthesizeddiscontinuously.
75What is this process called? Chapter 12Molecular GeneticsStandardized Test PracticeWhat is this process called?
76mRNA processing protein synthesis transcription translation Chapter 12Molecular GeneticsStandardized Test PracticemRNA processingprotein synthesistranscriptiontranslation
77TTCAGG TTCTGG What type of mutation results in this change Chapter 12Molecular GeneticsStandardized Test PracticeWhat type of mutation results in this changein the DNA sequence?TTCAGG TTCTGGdeletionframeshiftinsertionsubstitution
78How could RNA interference be used Chapter 12Molecular GeneticsStandardized Test PracticeHow could RNA interference be usedto treat diseases such as cancer anddiabetes?
79by activating genes to produce proteins that Chapter 12Molecular GeneticsStandardized Test Practiceby activating genes to produce proteins thatcan overcome the diseaseby interfering with DNA replication in cellsaffected by the diseaseby preventing the translation of mRNA intothe genes associated with the diseaseby shutting down protein synthesis in thecells of diseased tissues
80The structure of a protein can be altered Chapter 12Molecular GeneticsStandardized Test PracticeTrue or FalseThe structure of a protein can be altereddramatically by the exchange of a singleamino acid for another.