Chapter 5 - DNA deoxyribonucleic acid hereditary material double helix polarity(5 to 3 is key to function as hereditary material package in nucleus

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1 Chromosomes.j pg DNA deoxyribonucleic acid • hereditary material • double helix & polarity (5’ to 3’) is key to function as hereditary material • package in nucleus = chromosomes • visible during cell division • invisible most of the time DNA consist of two long polynucleotide chains (DNA strands) held together by H-bonds phosphate backbone has polarity - 5’ to 3’ four different bases - G, A, T & C form base pairs when in double helix deoxy… Unless indicated differently, a sequence is always written in the 5’to 3’ direction.
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2 H-bonds Note: 5’ to 3’ polarity Anti-parallel Base-pairs: ALWAYS A and T C and G low energy H-bonds 2 between A & T 3 between C & G purine (2 rings) pyrimidine (1 ring)
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3 05_07_base pairing.jpg base stacking yields strong interaction between strands Melting requires boiling. major_minor_gr. jpg Crystal structure - • double helix right-handed (i.e. as look at helix, strands face up to right) • red = phosphate backbone - common features • bases = stacked in middle can be “detected” if protein interacts in major or minor groove • allows specificity of an interaction [= gene regulation]
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4 05_03_Griffith.jpg How we know - Griffith (late 1920’s) demonstrates that heat killed bacteria can still transform living cells. colonies are smooth, slimy polysaccharide coat colonies are rough - no coat even if heat- inactivated, S-strain could transfer something to R-strain to transform it into a lethal strain. this something was also inheritable Transforming Principle: What was the something? Avery - + 15 years work made various extracts of S-strain Q: which molecules yields transformation it took awhile to except as it went against dogma of time Mix with R- strain
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5 More rigorous proof - Hershey & Chase (1950’s) made use of lytic T2 viruses and infected bacteria two batches of virus
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This note was uploaded on 04/02/2008 for the course BIO 2600 taught by Professor Vanburkem during the Winter '08 term at Wayne State University.

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Chapter 5 - DNA deoxyribonucleic acid hereditary material double helix polarity(5 to 3 is key to function as hereditary material package in nucleus

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