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Unformatted text preview: Chapter 7 Lecture notes Hereditary material Biologists hypothesized that hereditary material should have the following three properties: on next quiz 1. Have information content. You see here hereditary material has the genetic material to keep the certain pigments 2. Allow relatively faithful replication to provide for the kind of stability necessary. 3. Allow for rare changes in the information content that are capable of permanence. The development of the hypothesis that DNA is the genetic material. By the 1930s biologists began to speculate as to what sort of molecules could have these properties. ** Protein and not DNA was thought to be the genetic material just prior to the DNA hypothesis for two reasons. -space filling molecule 3Cro 1. Biologists believed that the genetic material would have to be complex 1 to carry all the information 2 to code for all the various life forms. 3 Biologists knew that protein was more complex than DNA because they were aware that protein is composed of 20 different monomers (amino acids) and that DNA was composed of only 4 monomers (The A, T, C, and G nucleotides). 2. Biologists also reasoned that the genetic material would need to be present in all parts of the cell (ubiquitous) means its all over the place in order to control all the activities of the cell. Biologists knew that protein was found in all portions of the cell and that the DNA was found primarily in the nucleus. Until the mid-1940s there appeared to be no method to directly approach the question of the genes chemical structure. Therefore, biologists began to approach the nature of the gene by attempting to determine how genes function within cells. The first clues as to how genes function came from studies of humans. Early in the twentieth century Archibald E. Garrod , an English physician, (p 187) hypothesized that several human diseases show metabolic defects in the metabolism. **** 1. Gerrod is the first to hypothesize that human disease could have genetic disorder 2. He focused our attention and said the function of the gene is to control metabolism He coined the idea that these defects were inborn errors in metabolism. ****2 nd big contribution restated Garrods observations focused attention on metabolic control as a primary way in which genes function....
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- Spring '08