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BIO311: Molecular Biology

Unit 1: Discovery of DNA and The Gene   The twisted ladder shape has become the symbol of genetics; it stands for the double stranded DNA. The basic principles of inheritance, the nature of DNA, and its significance in inheritance were all synthesized from experimental findings of scientists who were trained in a variety of disciplines. The inheritance patterns of traits were described without knowing the underlying molecular mechanisms, and the composition of DNA was determined without knowing its significance in inheritance. By 1950, it was determined that DNA is the hereditary material. In 1953, the structure of the DNA was published: the twisted ladder.

Unit 1 Time Advisory
This unit should take you approximately 10.5 hours to complete.

☐    Subunit 1.1: 0.5 hours

☐    Subunit 1.2: 3.0 hours

☐    Subunit 1.3: 4.5 hours

☐    Subunit 1.4: 1.5 hour

☐    Subunit 1.5: 1.0 hour

Unit1 Learning Outcomes
Upon successful completion of this unit, students will be able to: - Discuss the timeline of major discoveries in genetics. - Identify the genotype and phenotype of offspring if the inheritance is Mendelian. - Compare and contrast dominant, recessive, and co-dominant alleles. - Discuss genetic recombination, which is the exchange of genes between homologous chromosomes. - Discuss why jumping genes cause mutations. - Discuss the purification of nuclein and the identification of its composition. - Compare and contrast the Griffith and Avery experiments. - Compare and contrast the experiments that identified DNA as the transforming and DNA as the hereditary material. - Describe the experimental evidence and reasoning leading to the identification of DNA as the molecule that carries genetic information, as opposed to proteins, RNA, or other cellular metabolites. - Discuss the double helix model of DNA and the relative contributions of Chargaff, Crick, Franklin, Levene, and Watson to its experimental verification. - Describe the semi-conservative replication of DNA, its experimental evidence, and competing theories. - Discuss the central dogma.

1.1 The History of Genetics   - Reading: DNA Interactive's "Timeline" Link: CSHL: DNA Interactive's "Timeline" (Adobe Flash)
 
Instructions: Please use the DNA Interactive site to learn that our knowledge on inheritance and DNA is very recent.  The timeline of some of the great discoveries in DNA research is listed here.  It may help you to see these dates together with the time when, for example, color TV, air conditioning, or plastic was invented.
 
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1.2 Inheritance   1.2.1 Mendelian Inheritance   - Reading: Palomar College: Dr. Dennis O'Neil's "Mendel's Genetics" Link:  Palomar College: Dr. Dennis O'Neil's "Mendel's Genetics" (HTML)
 
Instruction:  Please study this page.  Mendel published his experiments on the plant hybridization in 1866.  He used Pisum sativum (pea plant) as a model organism.
 
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  • Web Media: Khan Academy’s “Punnett Square Fun” Link: Khan Academy’s “Punnett Square Fun” (Adobe Flash)
     
    Instructions: Please watch the video (26 min) for a step-by-step tutorial on using Punnett squares to determine how alleles of more than one gene assort independently.  During sexual reproduction both parents pass on some of their traits to their offspring(s).  Mendel's law of segregation describes how different versions of one trait are combined in the offspring.  Mendel's law of independent assortment describes how different versions of different traits are combined in the offspring.  Please make sure that you can predict the genotype and phenotype of the F1 generation using Punnett squares.  You may need to follow this video several times.  Be patient; it may take some time to get used to the Punnett squares.  This is a great tool, used every day in genetic counseling.
     
    Terms of Use: This video is licensed under a Creative Commons Attribution-NonCommercial-NoDerives United States License 3.0.  It is attributed to the Khan Academy. 

  • Assessment: Palomar College: Dr. Dennis O'Neil's "Practice Quiz for Mendel's Genetics" Link:   Palomar College:  Dr. Dennis O'Neil's "Practice Quiz for Mendel's Genetics" (HTML)
     
    Instruction:  Please complete the quiz.  A response will appear in the window after you make your choice.
     
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1.2.2 Genetic Recombination   - Reading: Scitable: Ingrid Lobo and Kenna Shaw’s "Thomas Hunt Morgan, Genetic Recombination, and Gene Mapping" Link: Scitable: Ingrid Lobo and Kenna Shaw’s "Thomas Hunt Morgan, Genetic Recombination, and Gene Mapping" (HTML)
 
Instructions:  Please study this page. Morgan published his work on "coupling" in Mendelian genetics in 1911.  He used Drosophila melanogaster (fruit fly) as a model organism. (HTML)
 
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1.2.3 Jumping Genes   - Reading: Scitable: Leslie Pray and Kira Zhaurova’s "Barbara McClintock and the Discovery of Jumping Genes (Transposons)" Link: Scitable: Leslie Pray and Kira Zhaurova’s "Barbara McClintock and the Discovery of Jumping Genes (Transposons)" (HTML)
 
Instructions:  Please study this page. Morgan published his work on "coupling" in Mendelian genetics in 1911.  McClintock published her work on jumping genes in 1951. She used Zea mays (maize) as a model organism.
 
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1.3 Genetic Material   1.3.1 Nuclein from Nucleus   - Reading: Brooklyn College: Prof. John Blamire's "Discovery of DNA" Link:  Brooklyn College: Prof. John Blamire's "Discovery of DNA" (HTML)
 
Instruction:  Please study this page.  Nuclein was a purified unique substance containing a lot of phosphorus besides hydrogen, carbon, oxygen, and nitrogen. Miescher published his work in 1871.   

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1.3.2 The Composition of Nuclein   - Reading: Scitable: Dr. Leslie A. Pray's "Discovery of DNA Structure and Function: Watson and Crick" Link:  Scitable: Dr. Leslie A. Pray's "Discovery of DNA Structure and Function: Watson and Crick" (HTML)
 
Instruction:  Please study the "Laying the Groundwork: Levene Investigates the Structure of DNA" section in this publication.  You have to navigate to "Page 2" using the "Next Page" link in the right bottom corner of this site.  Levene published his work in 1915.    
 
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1.3.3 Transforming Material   - Reading: Scitable: Dr. Clare O'Connor’s "Isolating Hereditary Material: Frederick Griffith, Oswald Avery, Alfred Hershey, and Martha Chase" Link: Scitable: Dr. Clare O'Connor’s "Isolating Hereditary Material: Frederick Griffith, Oswald Avery, Alfred Hershey, and Martha Chase" (HTML)
 
Instructions:  Please study the "Frederick Griffith Discovers Bacterial Transformation" section, including Figure 2.Griffith published his experiments in 1928. He used Mus musculus (mouse) and Streptococcus pneumoniae as model organisms.
 
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  • Web Media: YouTube: Classontheweb's "Griffith's Experiment" Link: YouTube: Classontheweb's "Griffith's Experiment" (YouTube)
     
    Instructions: Please watch this video (2:35 min).

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1.3.4 DNA Is the Transforming Material   - Reading: Scitable: Dr. Clare O'Connor: "Isolating Hereditary Material: Frederick Griffith, Oswald Avery, Alfred Hershey, and Martha Chase" Link: Scitable: Dr. Clare O'Connor: "Isolating Hereditary Material: Frederick Griffith, Oswald Avery, Alfred Hershey, and Martha Chase" (HTML)
 
Instructions:  Please study the "DNA Is Identified as the Transforming Principle" section, including Figure 3. Avery and his colleagues published their experiments in 1944. They used Streptococcus pneumoniae as a model organism.
 
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  • Web Media: CSHL: DNA Learning Center’s "A Gene Is Made of DNA" Link: CSHL: DNA Learning Center’s "A Gene Is Made of DNA" (Adobe Flash)
     
    Instructions:  Please watch this animation. You have to use the arrow at the right bottom corner to advance from slide to slide.
     
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1.3.5 One Gene—One Protein   - Reading: NCBI Bookshelf: Griffiths' "How Genes Work" Link:  NCBI Bookshelf: Griffiths' "How Genes Work" (HTML)
 
Instruction:  Please study this page.  Beadle and Tatum published their experiments in 1941.  They used Neurospora crassa as a model organism.
 
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  • Web Media: YouTube: Echaney's "AP Biology Beadle & Tatum" Link: YouTube: Echaney's "AP Biology Beadle & Tatum"(YouTube)
     
    Instructions:  Please watch this video (3 min).
     
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1.3.6 DNA Is the Hereditary Material   - Reading: Scitable: Dr. Clare O'Connor: "Isolating Hereditary Material: Frederick Griffith, Oswald Avery, Alfred Hershey, and Martha Chase" Link: Scitable: Dr. Clare O'Connor: "Isolating Hereditary Material: Frederick Griffith, Oswald Avery, Alfred Hershey, and Martha Chase" (HTML)
 
Instructions:  Please study the "DNA Is Identified as the Transforming Principle" section, including Figure 3. Hershey and Chase published their experiments in 1952. They used virus infected Escherichia coli as a model organism.
 
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1.3.7 Chargaff's Rules of Base Pairing, 1950   - Reading: University of Miami’s "Chargaff's Rule of Base Pairing" Link: University of Miami’s "Chargaff's Rule of Base Pairing" (HTML)
 
Instructions:  Please study this page.
 
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  • Web Media: CSHL: DNA Learning Center’s "Chargaff's Ratios" Link: CSHL: DNA Learning Center’s "Chargaff's Ratios" (Adobe Flash)
     
    Instructions:  Please watch this animation (1 min).
     
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1.3.8 DNA structure   - Reading: PBS: Nova’s “Anatomy of Photo 51” Link: PBS: Nova’s “Anatomy of Photo 51” (HTML)
 
Instructions: Please investigate the critical evidence that led to the model of the DNA double helix.  Rosalind Franklin’s X-ray diffraction image #51 is shown here.  Click on the “Launch interactive” button and advance step by step from image #51 to the double helix model of DNA.  Please note that all structural parameters of the double helix are provided by image #51. Franklin and Gosling published the structure of the A-form and B-form of DNA in 1953.
 
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1.4 DNA Replication is Semiconservative   - Reading: NCBI Bookshelf: Lodish et al.’s "General Features of Chromosomal Replication" Link: NCBI Bookshelf: Lodish et al.’s "General Features of Chromosomal Replication" (HTML)
 
Instructions:  Please read the "DNA Replication Is Semiconservative" section on this page.
 
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  • Reading: NCBI Bookshelf: Brown’s "Genome Replication" Link: NCBI Bookshelf: Brown’s "Genome Replication" (HTML)
     
    Instructions:  Please read "The Meselson-Stahl Experiment" and "Variations on the Semiconservative Theme" sections on this page.
     
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  • Assessment: University of Arizona: The Biology Project: "Problem 2: 14N Distribution after One Generation" and "Problem 6: Meselson-Stahl DNA Replication Experiment" Link:  University of Arizona: The Biology Project: "Problem 2: 14N Distribution after One Generation" and "Problem 6: Meselson-Stahl DNA Replication Experiment" (HTML)
     
    Instruction: Please complete these problems. After answering a question, please click on and study each tutorial page as well.
     
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1.5 The Central Dogma of Molecular Biology   - Reading: Scitable: Suzanne Clancy and William Brown's "Translation: DNA to mRNA to Protein" Link: Scitable:  Suzanne Clancy and William Brown's "Translation: DNA to mRNA to Protein" (HTML)
 
Instructions: Please study this page.
 
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