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Students will explain classical genetics at the molecular level Summarize the historical discovery of the DNA molecular structure by Franklin, Watson.

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Presentation on theme: "Students will explain classical genetics at the molecular level Summarize the historical discovery of the DNA molecular structure by Franklin, Watson."— Presentation transcript:

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2 Students will explain classical genetics at the molecular level Summarize the historical discovery of the DNA molecular structure by Franklin, Watson and Crick Describe how genetic information is contained in the sequence of bases in DNA Describe DNA replication

3 Some History 1928 –Frederick Griffith (British) Streptococcus Pneumoniae –Studied Streptococcus Pneumoniae pneumonia bacteria two genetic strains S typeColonies appeared smooth (S type) –Surrounded by a mucous coat or capsule R typeColonies that appeared rough (R type)

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16 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.

17 Thinking 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.

18 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.

19 Functions of DNA Controls cellular activities of an organism by 1.Coding for structural proteins 2.Coding for enzymes

20 Nucleic Acids DNA –Deoxyribonucleic Acid –Genetic material –Can self-replicate –Made up of Nucleotides Shape = double helix –A twisted rope ladder –A full twist every 10 nucleotides

21 DNA Discovery Rosalind Franklin was using X-Ray Diffraction to study DNA Her work allowed Watson and Crick to come up with model of DNA Findings presented in 1953 Visually confirmed in 1969

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24 Nucleotides Nucleotides are composed of –A sugar five carbons Deoxyribose –A phosphate PO 4 - –One of 4 nitrogen bases 1.Adenine [A] 2.Thymine [T] 3.Cytosine [C] 4.Guanine [G] The sugar- phosphate groups are the side rails of ladder and the the nitrogen bases are the rungs

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26 Nucleotides The two strands of DNA are complimentary because the nitrogen bases bond with each other according to some rules. 1.Adenine will only bond with Thymine 2.Guanine will only bond with Cytosine Nitrogen bases bond via hydrogen bonds. These break over 70 o C (denature)

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30 DNA REPLICATION DNA must have the ability to create an exact duplicate of itself The sequence in one strand determines precisely what the sequence of nucleotides in the other strand will be. (A-T, G-C)

31 DNA REPLICATION 1.The hydrogen bonds holding the two complimentary strands together break 2.DNA strands separate 3.Free floating complimentary nucleotides match up with nucleotides on the parent DNA strand. –Catalyzed by DNA polymerase 4.New, semi-conservative strands are formed

32 DNA REPLICATION Semi-conservative –The daughter strands are made up of one half old strand on one half new strand The 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.

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39 Students will explain classical genetics at the molecular level Describe RNA transcription Describe how genetic information is translated into amino acid chains in proteins Explain how mutations result in abnormalities or create genetic variability Explain how base sequences in nucleic acids give evidence for evolution

40 DNA vs RNA DNARNA

41 DNA vs RNA DNA Double stranded RNA

42 DNA vs RNA DNA Double stranded RNA Single stranded

43 DNA vs RNA DNA Double stranded Deoxyribose sugar RNA Single stranded

44 DNA vs RNA DNA Double stranded Deoxyribose sugar RNA Single stranded Ribose sugar

45 DNA vs RNA DNA Double stranded Deoxyribose sugar Nitrogen bases –Cytosine RNA Single stranded Ribose sugar

46 DNA vs RNA DNA Double stranded Deoxyribose sugar Nitrogen bases –Cytosine –Guanine RNA Single stranded Ribose sugar

47 DNA vs RNA DNA Double stranded Deoxyribose sugar Nitrogen bases –Cytosine –Guanine –Adenine RNA Single stranded Ribose sugar

48 DNA vs RNA DNA Double stranded Deoxyribose sugar Nitrogen bases –Cytosine –Guanine –Adenine –Thymine RNA Single stranded Ribose sugar

49 DNA vs RNA DNA Double stranded Deoxyribose sugar Nitrogen bases –Cytosine –Guanine –Adenine –Thymine RNA Single stranded Ribose sugar Nitrogen bases –Cytosine

50 DNA vs RNA DNA Double stranded Deoxyribose sugar Nitrogen bases –Cytosine –Guanine –Adenine –Thymine RNA Single stranded Ribose sugar Nitrogen bases –Cytosine –Guanine

51 DNA vs RNA DNA Double stranded Deoxyribose sugar Nitrogen bases –Cytosine –Guanine –Adenine –Thymine RNA Single stranded Ribose sugar Nitrogen bases –Cytosine –Guanine –Adenine

52 DNA vs RNA DNA Double stranded Deoxyribose sugar Nitrogen bases –Cytosine –Guanine –Adenine –Thymine RNA Single stranded Ribose sugar Nitrogen bases –Cytosine –Guanine –Adenine –Uracil [U]

53 DNA vs RNA DNA One type of DNA RNA

54 DNA vs RNA DNA One type of DNA RNA Many types of RNA

55 DNA vs RNA DNA One type of DNA RNA Many types of RNA –Messenger RNA (mRNA)

56 DNA vs RNA DNA One type of DNA RNA Many types of RNA –Messenger RNA (mRNA) –Transfer RNA (tRNA)

57 DNA vs RNA DNA One type of DNA RNA Many types of RNA –Messenger RNA (mRNA) –Transfer RNA (tRNA) –Ribosomal RNA (rRNA)

58 DNA 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)

59 DNA 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)

60 DNA 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

61 DNA vs RNA DNA One type of DNA Mostly in nucleus Can self-replicate under the right conditions RNA Many types of RNA –Messenger RNA (mRNA) –Transfer RNA (tRNA) –Ribosomal RNA (rRNA) –Small nuclear RNA (smRNA) Mostly found in cytoplasm

62 DNA vs RNA DNA One type of DNA Mostly in nucleus Can self-replicate under the right conditions RNA Many types of RNA –Messenger RNA (mRNA) –Transfer RNA (tRNA) –Ribosomal RNA (rRNA) –Small nuclear RNA (smRNA) Mostly found in cytoplasm Cannot self-replicate

63 Genes and Proteins A gene is a segment of DNA –Carries the information of the synthesis of a protein One gene codes for one protein

64 Proteins in the Body Enzymes Hormones Antibodies Hemoglobin Cell membranes Receptor molecules Carrier molecules

65 Composition of Proteins Made up of 20 different amino acids Sequence of a.a.’s identifies protein Sequence of bases in DNA determines Sequence of a.a.’s One gene = one protein Protein Synthesis relies on 3 types of RNA –rRNA –mRNA –tRNA

66 Types of RNA Ribosomal RNA (rRNA) –Makes up the ribosomes Messenger RNA (mRNA) –Involved in transcription (first stage of protein synthesis) –Carries message from DNA in nucleus to ribosome in cytoplasm Transfer RNA (tRNA) –carries amino acids to mRNA All RNA produced in nucleolus. tRNA & rRNA - In cytoplasm only mRNA in cytoplasm & nucleus

67 Protein Synthesis Occurs primarily in ribosomes Instructions for protein contained in DNA Message must get from nucleus to cytoplasm (DNA to ribosome) Process occurs in 2 steps –watch animations – click on the words below 1. Transcription1. Transcription 2. Translation2. Translation

68 Protein Synthesis Summary 1.mRNA is made using DNA template 2.mRNA exits nucleus 3.tRNA picks up aa’s 4.tRNA anticodon bonds to mRNA codon 5.Peptide bond forms between aa’s 6.Protein used by cell or packaged & exported 7.mRNA breaks into free nucleotides 8.tRNA’s free to pick up more aa’s Transcription Translation

69 Transcription In nucleus mRNA made using DNA as a template If the DNA base sequence is A A T T C C G G A (3 triplets) The mRNA molecule manufactured would be U U A A G G C C U (3 triplets) Each triplet is a codon

70 Code must be transcribed then translated

71 Transcription DNA used as template to build mRNA

72 mRNA built using DNA as a template

73 Initiation Elongation Termination

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75 Codons 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 methioine If code AUG is in middle it must code for methionine

76 Data table of mRNA codons supplied in diploma!! Can be used to work out DNA, tRNA or amino acid sequence

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78 Translation mRNA arrives at ribosome tRNA molecules with a.a.’s are attracted to this mRNA –complimentary rule (A attracts U etc….) 20 a.a.’s therefore –20 different tRNA’s

79 Translation mRNA U U A A G G C C U 3 codons

80 Translation mRNA U U A A G G C C U tRNA A A U U C C G G A 3 anticodons

81 Transfer RNA

82 Translation Initiation

83 Identify codons and anticodons

84 Identify peptide bonds, ribosome & protein

85 Translation 1

86 Translation 2

87 Translation 3

88 Translation 4

89 Translation 5 Name the products!

90 Translation Requires many Ribosomes

91 The golgi apparatus will package the protein to be used for different functions throughout the body.

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93 Review 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 =

94 Answers to Review Questions mRNA codon for AAT DNA triplet = UUA DNA triplet for CCG mRNA codon = GGC tRNA anticodon for GCA DNA triplet = GCA mRNA codon for GAU tRNA = CUA tRNA anticodon for UUA mRNA codon = AAU DNA triplet for CUA anticodon = CTA codon for UAG anticodon = AUC anticodon for CTA DNA triplet = CUA

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96 Mutations Changes in the sequence of bases in DNA Caused by mutagenic substances like –X-rays –cosmic rays –UV light –Some chemicals Mutagens 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.

97 Mutations 3 types of mutations. 1.INSERTION –An extra nucleotide is inserted into the DNA –Causes a frame shift 2.DELETION –A nucleotide is deleted from the DNA –Causes a frame shift 3.SUBSTITUTION –One nucleotide is substituted for another

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102 Using DNA to explain Evolution Species that are closely related will share very similar DNA sequences Scientists use mitochondrial DNA (mtDNA) to study the relationship between species Used to explain variety of ethnic groups found throughout the world (all from African descendents)

103 Using SINEs and LINEs SINEs and LINEs are repeated DNA sequences that don’t code for anything, but show an evolutionary relationship Finding 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

104 Students will explain classical genetics at the molecular level Explain DNA transformation –(recombinant DNA) Describe the role of restriction enzymes and ligases in transformation

105 Genetic Engineering A desired gene can be isolated and millions of copies made These copies can then be analyzed to determine the gene’s nucleotide sequence This nucleotide sequence can be decoded to find the sequence of amino acids in the corresponding protein

106 Genetic Engineering Functioning genes can be transferred into cells or bacteria, yeasts, plants, animals –i.e – Griffith made to ordergene machinesDNA can be “made to order” using “gene machines” that can be programmed to produce short strands of DNA in any desired sequence –Useful for studying DNA, –protein synthesis experiments Change genetic code to eliminate particular amino acids from a protein Find how the amino acid affects the protein’s function

107 Transformation Transformation 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.

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110 Genetic Engineering Recombinant DNA To recombine DNA –A technique to determine gene expression in vitro –Gene segments from different sources are recombined in vitro and transferred into cells (usually E. coli) to see what happens. Genetic Engineering Recombinant DNA

111 First successful GE experiment with human DNA took place in 1980 –Human 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 Genetic Engineering Recombinant DNA

112 1.The desired gene is isolated and cut out of the DNA A “restriction enzyme” (restriction endonuclease) does this 2.Isolated gene is inserted into a bacterial plasmid using a ligase Ligase is an enzyme which normally repairs breaks in the DNA backbone New DNA now called recombinant DNA Genetic Engineering Recombinant DNA – How It Works

113 Genetic Engineering Recombinant DNA 3.The plasmid is absorbed by a bacterium Reproduces asexually to produce many clones containing the recombinant DNA 4.Bacterial cells produce the protein coded by the foreign gene Desired protein can be isolated and purified from the culture. Genetic Engineering Recombinant DNA

114 Examples of recombinant DNA technology… Interferon Human growth hormone Human insulin Gene Therapy Agriculture… Genetic Engineering Recombinant DNA

115 Restriction Enzymes cut Ligase acts as glue rDNA

116 Recombinant DNA Technology Sticky end Restriction Enzyme

117 Gene insertion

118 Genetic Engineering Recombinant DNA Gene Therapy –Replacement of defective genes with normal healthy genes e.g. Cystic fibrosis, hemophilia, sickle-cell anemia, immune-deficiencies OBSTACLES today include … –How to fit genes into the body cells –How to control the introduced genes Genetic Engineering Recombinant DNA

119 Agriculture –Introduction of genes for resistance to disease, drought, frost, increased protein production, larger fruit…

120 Used in forensic studies… Small quantities of blood, semen, or other tissue can be tested for the DNA base sequence The 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 Genetic Engineering DNA Fingerprinting

121 Radioactive probes mark the bands that contain certain markers… –Only 5 or 10 regions of the entire genetic content of the cell are tested This was a defense argument used by the O.J. Simpson lawyers The probability of having matching DNA fingerprints is about 1 in a million. Genetic Engineering DNA Fingerprinting


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