BIOB11H3 Chapter Notes - Chapter 13: Deoxyribose, Dnac, Telomerase
29 Apr 2011
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Watson and crick hypothesized that dna replication is semiconservative - but they also had to consider the conservative and dispersive modes of replication as alternative hypotheses. If conservative, there should always be a heavy band - light band starts with the same amount, then increases everytime. If dispersive, first only hybrid band - then the whole band starts moving up towards the light region while increasing. If semiconservative, hybrid band should always be there and light band starts to increase from 0. Taylor showed that semiconservative replication also occur in eukaryotes. Cells were put in medium with bromodeoxyuridine (brdu) that is incorporated into dna in place of thymidine and could be contrasted with others after staining. After 2 generations, he found that one chromatid of each chromosome was composed of 2 brdu-containing strands, whereas the other chromatid was a hybrid. Separation of dna molecules creates topological problems (torsional stress). An overwound dna becomes positively supercoiled ahead of the www. notesolution. com fork.
