Unit 1-2 - Review of Unit 1-1 Experiments showing that DNA...

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Unformatted text preview: Review of Unit 1-1 Experiments showing that DNA is the genetic material Griffith Avery, MacLeod & McCarty Hershey & Chase The nucleotide Pentose sugar Nitrogenous base Phosphate group Tr ansfor mation of Str eptococcus pneumoniae Smooth (S) cells > death Rough (R) cells > mouse lives H eated S cells > mouse lives H eated S + live R > death Fig 2.2 Clicker Question (Example) The factor in the Griffith experiment that was able to transform avirulent rough cells into virulent smooth cells was A. The polysaccharide coat B. The genes that coded for enzymes necessary to generate the polysaccharide coat C. Protein and DNA D. RNA Clicker Answer (Example) The factor in the Griffith experiment that was able to transform avirulent rough cells into virulent smooth cells was A. The polysaccharide coat B.The genes that coded for enzymes necessar y to gener ate the polysacchar ide coat C. Protein and DNA D. RNA Fr actionate dead S cells (For mer ly Vir ulent) S Combine tr eated S cell fr actions with avir ulent R cells I nject mice N o tr eatment +SI I I (degr ades polysacchar ides) +Pr otease (degr ades pr otein) +RN ase (degr ades RN A) +DN ase (degr ades DN A) R No treatment +SI I I +Protease +RNase +DNase Spin cells gently in centr ifuge Wher e is the major ity of r adioactivity? Pellet (cells) Super natant (phage coats) 35 S-labeled 32 D. The nucleotide N ucleoside plus phosphate = nucleotide N ote: to distinguish between sugar and base, positions in the sugar ar e designated with pr ime () Unit 1-2 I I I . The Physical Str uctur e of DN A Backgr ound Linear str uctur e was known phosphate bonds link sugar s, base linked to sugar H ow could this appar ently simple molecule hold enough infor mation to be the genetic mater ial? Does the 3-dimensional str uctur e give us a clue? Char gaff's r ule: Base r atio analysis of DN A indicated that DN A was not a r andom polymer An impor tant piece of the puzzle A: 29 30 26 T: 31 29 24 G: 18 18 21 C: 18 15 17 96 92 88 % r ecover ed H uman yeast bovine % of differ ent bases in DN A samples fr om differ ent sour ces The amount of Adenine = Thymine The amount of Guanine = Cytosine (A G or C, T C or G) G + C does not always equal A + T Base Pair ing Rules Figur e 2.13 Maur ice Wilkins and Rosalind Fr anklin at Kings College, London James Watson and Fr ancis Cr ick at Cavendish Labs, Cambr idge Who wants to know the str uctur e? X-r ay Diffr action Analysis of DN A Cr ystals: Deter mined Double H elix Str uctur e of DN A N obel Pr ize awar ded for this discover y (1962) Str uctur e deter mined I n 1953 http:/ / www.chem.yale.edu/ ~chem125/ 125/ xray/ diffract.html#Franklin Figur e 2.12 Fr anklins x-r ay diffr action pictur es showed a simple, r egular ly r epeating str uctur e, likely to be a helix Suggested that DN A molecule was: 1. Long and thin with a 2 nm diameter 2. Coiled in a helix 3. H ad r epeating patter ns ever y 0.34 nm and 3.4 nm (3.4 and 34 ) 4. Ther e might be 2 str ands 5. 2nm wide diameter : 5....
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This note was uploaded on 06/17/2010 for the course BIOLOGY Bio 107A taught by Professor Zarate during the Spring '09 term at UC Riverside.

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Unit 1-2 - Review of Unit 1-1 Experiments showing that DNA...

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