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STRUCTUREOF

MACROMOLECULES

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 The Structure of DNA

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•  The Double Helix Is Stabilize b! "ase#airi$% a$ "ase Stac&i$%'

•

H!ro%e$ "o$i$% Is I()orta$t for theS)eci*cit! of "ase #airi$%

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DNA Is Usuall! a Ri%ht+Ha$e Double Helix

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 The Double Helix Has Mi$or a$ Ma,or -roo.es

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The Double Helix Exists i$Multi)le Co$for(atio$s

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DNA Stra$s Ca$Se)arate/De$ature0 a$

Reassociate'a )he$o(e$o$&$o1$as h!)erchro(icit!'

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 The (i)oi$t of thistra$sitio$ is themelting pointor T(

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Nucleoso(es I$trouce Ne%ati.eSu)ercoili$% i$ Eu&ar!otes

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 To)oiso(erases Ca$ Relax Su)ercoile DNA

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 The Structure a$

2ersatilit! of RNA

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DIRECTED E2OLUTION SELECTS RNAs THAT"IND SMALL MOLECULES3Researchers ha.e ta&e$ a.a$ta%e of the )ote$tial structuralco()lexit! of 

RNA to %e$erate $o.el RNA s)ecies /$ot fou$ i$ Nature0 that ha.es)eci*cesirable )ro)erties b! a )rocess of irecte e.olutio$ &$o1$ asSELE4/for s!ste(atic e.olutio$ of li%a$s b! ex)o$e$tial e$rich(e$t0'

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SOME RNAs ARE EN56MES

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A Riboz!(e at the Heart of the Riboso(e Acts o$ aCarbo$ Ce$ter

• All of the exa()les co$siere so far are riboz!(es thatact o$ )hos)horous ce$ters'

• O$e of the RNA co()o$e$ts of the riboso(e7 8hich 1astraitio$all! thou%ht to ser.e o$l! a structural role7 is

$o1 &$o1$ to be the e$z!(e )e)ti!l tra$sferase71hich is res)o$sible for )e)tie+bo$ for(atio$ uri$%)rotei$ s!$thesis' I$ this case7 the riboz!(e acts o$ acarbo$ ce$ter rather tha$ a )hos)horous ce$ter i$catal!zi$% the reactio$' I$ aitio$7 the isco.er! that

o$e of the (ost fu$a(e$tal e$z!(atic reactio$s i$li.i$% cells is catal!ze b! a$ RNA (olecule has bee$ta&e$ as su))ort for the h!)othesis that co$te()orar!7)rotei$+base life arose fro( a$ earlier RNA8orl'

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 The Structure of #rotei$s

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