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Unformatted text preview: Biologists hypothesized that hereditary material should have the following three properties: 1) Have information content. 2)Allow relatively faithful replication to allow for the kind of stability necessary. 3) a: Allow for rare changes in the information content that are b: capable of permanence. ___________________________ PROTEIN and not DNA was thought to be the genetic material just prior to the DNA hypothesis for two reasons: 1) Biologists believed that the genetic material would have to be COMPLEX to carry all the information to code for all the various forms of life. *Biologists knew that protein was more complex than DNA because they were well aware that protein is composed of TWENTY different monomers (amino acids) and that DNA was composed of only FOUR 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) in order to control all the activities of the cell. *Biologists knew that protein was found in all portions of the cell and that DNA was found primarily in the nucleus. ________________________________________________________ ARCHIBALD E. GARROD hypothesized that several human diseases show "inborn errors in metabolism", which focused our attention on the genetic control of metabolism and showed us that human disease could be genetic. George BEADLE and Edward TATUM spearheaded research in the 1940s on the pink bread mold Neurospora crassa, which generated observations congruent with Garrod's hypothesis that GENES WORK BY CONTROLLING THE SYNTHESIS OF ENZYMES. _________________________________________________________ Tenets of Beadle and Tatum's "one gene-one enzyme" hypothesis: *Every locus produces a protein. (Falsification: some loci produce RNA such as tRNA) *Every locus produces one unique protein. (Falsification: Eukarya with post-transcriptional processing can produce more than one protein from each locus.) *Every protein was an enzyme (Falsification: Some proteins are functional, not all are enzymes such as hemoglobin) *Every enzyme had one unique metabolic function. (There's probably a falsification but Pierson tired of it and moved on) ____________________________________________________________ "Humorously, the one-gene-one-enzyme hypothesis caused a problem for biologists thinking that protein was the hereditary material. If Beadle and Tatum were right, the hereditary protein would have to have at least two enzymatic functions: 1) replicate self...
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This note was uploaded on 11/11/2009 for the course BIO Genetics taught by Professor Saxena during the Spring '08 term at University of Texas at Austin.
- Spring '08