Biology Chapter 16


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Chapter 16 THE MOLECULAR BASIS OF INHERITANCE GENES CARRY INFORMATION Early geneticists thought that genes were made of proteins. Archibald Garrod (1908) introduced the idea that genes and enzymes are related. Discussed the genetic disease alkaptoneuria. Homogentisic acid (HA), an intermediate of the breakdown of  phenylalanine and tyrosine, is excreted in the urine. Garrod theorized that an enzyme that oxidizes HA was lacking and that  this was due to a mutation of the gene. James Sumner (1926) showed that enzymes were proteins. Frederick Griffith (1928) converted avirulent pneumococcus to the virulent strain. Experiment with mice injected with avirulent live cells and heat-killed  virulent cells. Avirulent cells were converted to virulent cells. Transformation due to a transforming principle O.T. Avery, C.M. McLeod and M. McCarty (1944) identified the transforming principle to  be DNA.  George Beadle and Edward Tatum (1940s) suggested that a single gene specifies each  protein. They worked with fungus Neurospora crassa. Neurospora is a haploid organism. One gene, one protein hypothesis. Alfred Hershey and Martha Chase (1952) conducted experiments on the reproduction of  bacteriophages.
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They showed that DNA enters the cell. DNA is required for synthesis of new protein coats and DNA. Erwin Chargaff (1950) determined the composition of DNA: ratios of adenine-thymine  and guanine-cytosine were very close to 1. Rosalind Franklin and M.H. Wilkins conducted experiments on the x-ray diffraction of the  DNA molecule. James Watson and Francis Crick (1953) proposed a model for the structure of the DNA  molecule based on the work done by Franklin and Wilkins. They proposed the double  helix structure. DEOXYRIBONUCLEIC ACID - DNA 1. DNA, a polymer, is made of two polynucleotide chains intertwined to form a  double helix. 2. Each nucleotide monomer contains a nitrogenous base which may be one of the  Purines: adenine or guanine          or   Pyrimidine: thymine or cytosine.
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This note was uploaded on 11/22/2010 for the course BIOLOGY 101 taught by Professor None during the Spring '10 term at Kent State.

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