29. DNA Structure,Replication, And Repair(PART 1, WQS)

8/16/2019 29. DNA Structure,Replication, And Repair(PART 1, WQS)

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UNIT VI:

Storage and Expression of Genetic Information

CHAPTER 2:

!NA Str"ct"re# Rep$ication# and Repair

%INGS&NG 'ANGASS&CIATE PR&(ESS&R!EPT) of *I&CHE+ISTR, - +&.ECU.AR *I&.&G,# H+U

/0s2113145)com


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UNIT VI: Storage and Expression of

Genetic Information Chapter 29: !NA Str"ct"re# Rep$ication and Repair

Chapter 30: RNA Str"ct"re# S6nt7esis and

Processing Chapter 3: Protein S6nt7esis

Chapter 32: Reg"$ation of Gene Expression

Chapter 33: *iotec7no$og6 and H"man !isease


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*AC8GR&UN!

NUC!E"TI#E ST$UCTU$E


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I% NUC!E"TI#E ST$UCTU$E

N"c$eotides are composed of a nitrogeno"s 9ase# a pentose monosacc7aride# and one#t/o# or t7ree p7osp7ate gro"ps)

T7e nitrogencontaining 9ases 9e$ong to t/ofami$ies of compo"nds: t7e p"rines and t7e

p6rimidines)

&% '(rine and p)rimidine str(ct(res

*ot7 !NA and RNA contain t7e same p"rine 9ases: adenine A; and g"anine G;) *ot7!NA and RNA contain t7e p6rimidinec6tosine C;# 9"t t7e6 differ in t7eir second

p6rimidine 9ase: !NA contains t76mine T;#

/7ereas RNA contains "raci$ U;) T and Udiffer in t7at on$6 T 7as a met76$ gro"p)


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Un"s"a$ modified; 9ases are

occasiona$$6 fo"nd in somespecies of !NA and RNA# forexamp$e# in some


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C% N(c+eotides

T7e addition of one or more p7osp7ategro"ps to a n"c$eoside prod"ces an"c$eotide) T7e first p7osp7ate gro"pis attac7ed 96 an ester $inage to t7eB>&H of t7e pentose) T7e second andt7ird p7osp7ates are eac7 connected to

t7e n"c$eotide 96 a ?7ig7>energ6@ 9ond)

Note: T7e p7osp7ate gro"ps areresponsi9$e for t7e negati


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I% "VE$VIE,

T7e f$o/ of information from !NAto RNA to protein is termed t7e?centra$ dogma@ of

mo$ec"$ar 9io$og6# and is descripti


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N"c$eic acids are re0"ired for t7estorage and expression of geneticinformation)

!NA and RNA

!NA: t7e repositor6 of geneticinformation

E"ar6otic organisms: n"c$e"s#mitoc7ondria and t7e c7$orop$asts of

p$ants)

Proar6otic ce$$s# /7ic7$ac n"c$ei# 7a


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'7at is a c7romosome


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T7e !NA contained in a ferti$iFed egg encodes t7einformation t7at directs t7e de


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II% ST$UCTU$E "- #N&

!NA is a po$6mer of deox6ri9on"c$eoside monop7osp7atescostranded ss; !NA - !o"9$estranded ds; !NA

T7e t/o strands /ind aro"nd eac7 ot7er# forming a do"9$e7e$ix)

In e"ar6otic ce$$s# !NA is fo"nd associated /it7 9o"nd region no/n ast7e n"c$eoid)


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&% 3./. 'hosphodiester 1onds

*% #o(1+e he+ix

C% !inear and circ(+ar #N& mo+ec(+es


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-ig(re 29%2

A) !NA c7ain /it7 t7e n"c$eotide se0"ence s7o/n /ritten in t7e B 5B direction) A 5B B>p7osp7odiester

9ond is s7o/n 7ig7$ig7ted in t7e 9$"e 9ox# and t7e deox6ri9ose>p7osp7ate 9ac9one is s7aded in 6e$$o/)

*) T7e !NA c7ain /ritten in a more st6$iFed form# emp7asiFing t7e ri9osep7osp7ate 9ac9one)

C) A simp$er representation of t7e n"c$eotide se0"ence) !) T7e simp$est and most common; representation#

/it7 t7e a99re


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#o(1+e he+ix


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#o(1+e he+ix

In t7e do"9$e 7e$ix# t7e t/o c7ains are coi$ed aro"nd acommon axis ca$$ed t7e axis of s6mmetr6)

T7e c7ains are paired in an antipara$$e$ manner# t7at is#t7e J>end of one strand is paired /it7 t7e 5K>end of t7eot7er strand)

In t7e !NA 7e$ix# t7e 76drop7i$icdeox6ri9osep7osp7ate 9ac9one of eac7 c7ain is on t7eo"tside of t7e mo$ec"$e# /7ereas t7e 76drop7o9ic 9asesare staced inside)

T7e o


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A maLor /ide; groo


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% *ase pairing:

T7e 9ases of one strand of !NA are paired

/it7 t7e 9ases of t7e second strand# so t7atan adenine is a$/a6s paired /it7 a t76mineand a c6tosine is a$/a6s paired /it7 ag"anine)

T7erefore# one po$6n"c$eotide c7ain of t7e

!NA do"9$e 7e$ix is a$/a6s t7e comp$ementof t7e ot7er) Gi


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T7e 9ase pairs are 7e$d toget7er 9676drogen 9onds: t/o 9et/een A and Tand t7ree 9et/een G and C)

T7ese 76drogen 9onds# p$"s t7e76drop7o9ic interactions 9et/een t7estaced 9ases# sta9i$iFe t7e str"ct"reof t7e do"9$e 7e$ix)


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Ho/ is a !NA do"9$e 7e$ix formed


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Practice Activity


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T7e ri9on"c$eotide po$6mer >GTGATCAAGC>

co"$d on$6 form a do"9$e>stranded str"ct"re/it7:

A; >CACTAGTTCG> *; >CACUAGUUCG>

C; >GCTTGATCAC>

!; >GCUUGAUUAC>


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2% Separation of the to #N& strands in the do(1+ehe+ix:

T7e t/o strands of t7e do"9$e 7e$ix separate /7en

76drogen 9onds 9et/een t7e paired 9ases aredisr"pted) !isr"ption can occ"r in t7e $a9orator6 if t7e pH of t7e

!NA so$"tion is a$tered so t7at t7en"c$eotide 9ases ioniFe# or if t7e so$"tion is 7eated)

'7en !NA is 7eated# t7e temperat"re at /7ic7 one7a$f of t7e 7e$ica$ str"ct"re is $ost is defined as t7eme$ting temperat"re Tm;)

T7e $oss of 7e$ica$ str"ct"re in !NA# ca$$eddenat"ration# can 9e monitored 96 meas"ring itsa9sor9ance at 24 nm) *eca"se t7ere are t7ree76drogen 9onds 9et/een G and C 9"ton$6 t/o 9et/een A and T# !NA t7at contains 7ig7

concentrations of A and T denat"res at a $o/ertemperat"re t7an G> and C>ric7 !NA) Under appropriate conditions# comp$ementar6

!NA strands can reform t7e do"9$e 7e$ix 96 t7e process ca$$ed renat"ration or reannea$ing;)


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C% !inear and circ(+ar #N& mo+ec(+es

Eac7 c7romosome in t7e n"c$e"s of a e"ar6ote contains one $ong#$inear mo$ec"$e of ds!NA# /7ic7 is 9o"nd to a comp$ex mixt"re of proteins 7istone and non>7istone# see p) ; to form c7romatin)

E"ar6otes 7a


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E"ar6otic

organisms:n"c$e"s#mitoc7ondria andt7e c7$orop$asts of

p$ants)

Proar6otic ce$$s#/7ic7$ac n"c$ei# 7a


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29. DNA Structure,Replication, And Repair(PART 1, WQS)

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