Ch11-DNA and its Role in Heridity

Ch11-DNA and its Role in Heridity - 11 DNA and Its Role in...

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11 DNA and Its Role in Heredity
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11 DNA and Its Role in Heredity 11.1 What Is the Evidence that the Gene Is DNA? 11.2 What Is the Structure of DNA? 11.3 How Is DNA Replicated? 11.4 How Are Errors in DNA Repaired? 11.5 What Are Some Applications of Our Knowledge of DNA Structure and Replication?
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11.1 What Is the Evidence that the Gene Is DNA? By the 1920s, it was known that chromosomes consisted of DNA and proteins. A new dye stained DNA and provided circumstantial evidence that DNA was the genetic material: It was in the right place It varied among species It was present in the right amount
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11.1 What Is the Evidence that the Gene Is DNA? 1- Frederick Griffith , working with two strains of Streptococcus pneumoniae determined that a transforming principle ” from dead cells of one strain produced a heritable change in the other strain.
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11.1 What Is the Evidence that the Gene Is DNA? 2- Identifying the transforming principle, Oswald Avery : Treated samples to destroy different molecules; if DNA was destroyed, the transforming principle was lost.
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11.1 What Is the Evidence that the Gene Is DNA? 3- Hershey-Chase experiment: Determined whether DNA or protein is the genetic material using bacteriophage T2 virus. Bacteriophage proteins were labeled with 35 S ; the
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Figure 11.4 The Hershey–Chase Experiment
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11.1 What Is the Evidence that the Gene Is DNA? 4- Next, genetic transformation of eukaryotic cells was demonstrated— called transfection . Use a genetic marker—a gene that confers an observable phenotype. Any cell can be transfected, even an egg cell—results in a transgenic organism .
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11.2 What Is the Structure of DNA? The structure of DNA was determined using many lines of evidence. 1- One crucial piece came from X-ray crystallography . A purified substance can be made to form crystals; position of atoms is inferred by the pattern of diffraction of X-rays passed through it.
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11.2 What Is the Structure of DNA? 2- Chemical composition also provided clues: DNA is a polymer of nucleotides : deoxyribose , a phosphate group , and a nitrogen-containing base . The bases: Purines : adenine ( A ), guanine ( G ) Pyrimidines : cytosine ( C ), thymine ( T ) 3- 1950: Erwin Chargaff found in the DNA from many different species: amount of A = amount of T amount of C = amount of G Or, the abundance of purines = the abundance of pyrimidines— Chargaff’s rule .
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Figure 3.23 Nucleotides Have Three Components repeat fig 3.23 here
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11.2 What Is the Structure of DNA?
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Ch11-DNA and its Role in Heridity - 11 DNA and Its Role in...

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