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Unformatted text preview: -1-LECTURE 1016 September 2009 (P. J. Hollenbeck)BIOL231DNA and Chromatin Structure Read pp. 171-193; note pp. 174-76; DVD 5.1, 2Probs: Q5-6, 5-11 in ECB<So far this semester we have addressed how the cell is organized, how its boundaries work, whatmacromolecules are important for its function – and we have seen that the heavy lifting in the cell ismainly done by proteins. We have considered protein structure and function, and enzyme kinetics. Now we want to consider how proteins are synthesized and localized in the cell. To do this we beginwith the genetic information that encodes primary protein structure: the genome, comprised of DNA. Let’s consider it’s structure now, creeping up on it from general to specific...>I. Basic Organization of DNA[figs 5-2 to 5-7; DVD 5.1]<When the chemical basis of heredity was being elucidated, a number of now “classic” experimentswere carried out. You will learn about these in detail in your genetics course, but it is worth thinkingabout three now – Griffith’s S. pneumoniae experiment; Avery’s “transforming principle” expt, and theHersey-Chase expt. Study pp. 174-176 of your text for a good summary. These set the stage for thedetermination in the early 1950s of the double helix structure of DNA by Watson & Crick (andWilkins and Franklin). It is hard to appreciate how completely biology was changed by that singlefinding. The structure immediately revealed, in broad terms, how the genome replicates faithfully –that is, how the DNA instructions are copied.>(A) Structure and heredity – spectacular example of structure-function relationships(1) Replication – As soon as this structure was determined, it became apparent that ifthe two strands are separated, and a new strand is formed along each of them bycomplimentary base pairing (A:T , G!C), then the result will be two new helices eachwith identical structure – identical nucleotide sequences – to the original. At a stroke,this solved the long-standing problem of how biological information is carried faithfullyfrom generation to generation. (2) Transcription – We will get to this soon, but it is equally clear that an RNA copy ofany part of the DNA can be made in a similar fashion, and exported to the cytoplasm fortranslation (while the DNA remains safe and sound in the nucleus)....
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This note was uploaded on 12/18/2009 for the course BIOL 101 taught by Professor Wormer during the Fall '08 term at Purdue University.
- Fall '08