Chapter16 Molecular Basis of Inheritance

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    PowerPoint Lectures for

    Biology, Seventh Edition

    Neil Campbell and Jane Reece

    Lectures by Chris Romero

    Chapter 16

    he !olecular Basis o"

    Inheritance

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    Overview: Lifes Operating Instructions

    In 1953, James Watson an !rancis "ric#

    s$oo# t$e wor%

    # Wit$ an e%egant ou&%e'$e%ica% moe% for t$e

    structure of eo()ri&onuc%eic aci, or *+

    Figure 16.1

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    *+, t$e su&stance of in$eritance

    # Is t$e most ce%e&rate mo%ecu%e of our time

    -ereitar) information

    # Is encoe in t$e c$emica% %anguage of *+an reprouce in a%% t$e ce%%s of )our &o)

    It is t$e *+ program

    # .$at irects t$e eve%opment of man) ifferent

    t)pes of traits

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    "oncept 1/01: *+ is t$e genetic materia%

    ar%) in t$e 2t$ centur)

    # .$e ientification of t$e mo%ecu%es of

    in$eritance %oome as a ma4or c$a%%enge to

    &io%ogists

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    The Search for the Genetic Material:Scientific Inquiry

    .$e ro%e of *+ in $ereit)

    # Was first wor#e out &) stu)ing &acteria ant$e viruses t$at infect t$em

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    Evidence That DNA Can Transform acteria

    !reeric# riffit$ was stu)ing Streptococcus

    pneumoniae# &acterium t$at causes pneumonia in

    mamma%s

    -e wor#e wit$ two strains of t$e &acterium

    # pat$ogenic strain an a nonpat$ogenic

    strain

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    riffit$ foun t$at w$en $e mi(e $eat'#i%%e

    remains of t$e pat$ogenic strain# Wit$ %iving ce%%s of t$e nonpat$ogenic strain,

    some of t$ese %iving ce%%s &ecame pat$ogenic 6acteria of t$e 78 smoot$; strain of Streptococcus pneumoniaeare pat$ogenic &ecause t$e)

    $ave a capsu%e t$at protects t$em from an anima%s efense s)stem0 6acteria of t$e 7

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    riffit$ ca%%e t$e p$enomenon transformation

    # +ow efine as a c$ange in genot)pe anp$enot)pe ue to t$e assimi%ation of e(terna%

    *+ &) a ce%%

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    Evidence That !iral DNA Can "ro#ram Cells

    itiona% evience for *+ as t$e genetic

    materia%# "ame from stuies of a virus t$at infects

    &acteria

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    >iruses t$at infect &acteria, &acteriop$ages

    # re wie%) use as too%s &) researc$ers inmo%ecu%ar genetics

    Figure 16."

    Phage

    head

    Tail

    Tail #i$er

    %N&

    'a(terial

    (ell

    133nm

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    %fre -ers$e) an =art$a "$ase

    # Performe e(periments s$owing t$at *+ ist$e genetic materia% of a p$age #nown as .2

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    .$e -ers$e) an "$ase e(periment In t$eir famous 1952 e(periment, %fre -ers$e) an =art$a "$ase use raioactive su%fur

    an p$osp$orus to trace t$e fates of t$e protein an *+, respective%), of .2 p$ages t$at infecte &acteria% ce%%s0

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    rwin "$argaff ana%)Be t$e &ase composition of *+

    # !rom a num&er of ifferent organisms

    In 19AC, "$argaff reporte

    # .$at *+ composition varies from one species to

    t$e ne(t

    .$is evience of mo%ecu%ar iversit) among species

    # =ae *+ a more crei&%e caniate for t$e genetic

    materia%

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    Building a Structural Model of DNA:Scientific Inquiry

    Once most &io%ogists were convince t$at *+

    was t$e genetic materia%# .$e c$a%%enge was to etermine $ow t$e

    structure of *+ cou% account for its ro%e in

    in$eritance

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    =aurice Wi%#ins an

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    Figure 16.3a2 (

    "

    .

    .

    "

    "

    "

    .

    .

    .

    .

    "

    .

    03A nm

    30A nm

    /a0 4e #eatures o# %N& stru(ture

    1 nm

    /(0 Spa(e+#illi-g 5odel

    .

    Watson an "ric# euce t$at *+ was a

    ou&%e $e%i(# .$roug$ o&servations of t$e D'ra)

    cr)sta%%ograp$ic images of *+

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    !ran#%in $a conc%ue t$at *+

    # Was compose of two antipara%%e% sugar'p$osp$ate &ac#&ones, wit$ t$e nitrogenous

    &ases paire in t$e mo%ecu%es interior

    .$e nitrogenous &ases

    # re paire in specific com&inations: aenine

    wit$ t$)mine, an c)tosine wit$ guanine

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    O

    @O O

    O-

    O

    @OO

    O

    -2"

    O

    @OO

    O

    -2"

    O

    @OO

    O

    O-

    O

    O

    O.

    "

    "

    .

    O

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    O

    "-2

    OO@

    OO

    "-2

    "-2

    "-2

    5en

    -)rogen &on

    3en

    3en

    P

    P

    P

    P

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    O

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    P

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    OO

    O

    P

    /$0 Partial (he5i(al stru(ture

    -2"

    5enFigure 16.3$

    O

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    Watson an "ric# reasone t$at t$ere must &e

    aitiona% specificit) of pairing# *ictate &) t$e structure of t$e &ases

    ac$ &ase pair forms a ifferent num&er of

    $)rogen &ons

    # enine an t$)mine form two &ons,

    c)tosine an guanine form t$ree &ons

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    + - O "-3

    +

    +

    O

    +

    +

    +

    + -

    8ugar

    8ugar

    &de-i-e /&0 Th5i-e /T0

    +

    +

    +

    +

    8ugar

    O - +

    -

    +-

    + O-

    -

    +

    8ugar

    ua-i-e /0 Ctosi-e /C0Figure 16.7

    -

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    "oncept 1/02: =an) proteins wor# toget$er in

    *+ rep%ication an repair .$e re%ations$ip &etween structure an

    function

    # Is manifest in t$e ou&%e $e%i(

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    The Basic rinci!le: Base airing to a Tem!late Strand

    8ince t$e two strans of *+ are

    comp%ementar)# ac$ stran acts as a temp%ate for &ui%ing a

    new stran in rep%ication

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    In *+ rep%ication

    # .$e parent mo%ecu%e unwins, an two newaug$ter strans are &ui%t &ase on &ase'

    pairing ru%es

    /a0.$e parent mo%ecu%e $as two

    comp%ementar) strans of *+0

    ac$ &ase is paire &) $)rogen

    &oning wit$ its specific partner,

    wit$ . an wit$ "0

    /$0.$e first step in rep%ication is

    separation of t$e two *+

    strans0

    /(0 ac$ parenta% stran now

    serves as a temp%ate t$at

    etermines t$e orer of

    nuc%eoties a%ong a new,

    comp%ementar) stran0

    /d0 .$e nuc%eoties are connecte

    to form t$e sugar'p$osp$ate

    &ac#&ones of t$e new strans0

    ac$ 7aug$ter *+

    mo%ecu%e consists of one parenta%

    stran an one new stran0

    &

    C

    T

    &

    &

    C

    T

    &

    &

    C

    T

    &

    &

    C

    T

    &

    T

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    T

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    T

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    T

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    &

    &

    C

    T

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    T

    &

    T

    C

    T

    &

    T

    C

    T

    &

    T

    C

    T

    &

    T

    C

    Figure 16.8 a9d

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    Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 16.1: a9(

    Co-ser;ati;e

    5odel..$e two

    parenta% stransreassociate

    after acting astemp%ates fornew strans,

    t$us restoring

    t$e parenta%ou&%e $e%i(0

    Se5i(o-ser;ati;e

    5odel. .$e twostrans of t$eparenta% mo%ecu%e

    separate,an eac$ functions

    as a temp%ate

    for s)nt$esis ofa new, comp%e'

    mentar) stran0

    %ispersi;e

    5odel.ac$

    stran of both

    aug$ter mo%'

    ecu%es containsa mi(ture of

    o% an new%)

    s)nt$esiBe*+0

    Pare-t (ell

    First

    repli(atio-Se(o-drepli(atio-

    *+ rep%ication is semiconservative

    # ac$ of t$e two new aug$ter mo%ecu%es wi%%$ave one o% stran, erive from t$e parent

    mo%ecu%e, an one new%) mae stran/a0

    /$0

    /(0

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    (periments performe &) =ese%son an 8ta$%

    # 8upporte t$e semiconservative moe% of *+rep%ication

    Figure 16.11

    =att$ew =ese%son an !ran#%in 8ta$% cu%ture E. coli&acteria for severa% generations

    on a meium containing nuc%eotie precursors %a&e%e wit$ a $eav) isotope of nitrogen, 15+0 .$e &acteria

    incorporate t$e $eav) nitrogen into t$eir *+0 .$e scientists t$en transferre t$e &acteria to a meium wit$

    on%) 1A+, t$e %ig$ter, more common isotope of nitrogen0 n) new *+ t$at t$e &acteria s)nt$esiBe wou% &e

    %ig$ter t$an t$e parenta% *+ mae in t$e 15+ meium0 =ese%son an 8ta$% cou% istinguis$ *+ of ifferentensities &) centrifuging *+ e(tracte from t$e &acteria0

    EXPERIMENT

    .$e &ans in t$ese two centrifuge tu&es represent t$e resu%ts of centrifuging two *+ samp%es from t$e f%as#

    in step 2, one samp%e ta#en after 2 minutes an one after A minutes0

    RESULTS

    6acteria

    cu%ture in

    meium

    containing15+

    6acteria

    transferre to

    meium

    containing1A+

    !1

    *+ samp%e

    centrifuge

    after 2 min

    after first

    rep%ication;

    " *+ samp%e

    centrifuge

    after A min

    after secon

    rep%ication;

    *

    Less

    ense

    =ore

    ense

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    CONCLUSION =ese%son an 8ta$% conc%ue t$at *+ rep%ication fo%%ows t$e semiconservative

    moe% &) comparing t$eir resu%t to t$e resu%ts preicte &) eac$ of t$e t$ree moe%s in !igure 1/010

    .$e first rep%ication in t$e 1A+ meium prouce a &an of $)&ri 15+@1A+; *+0 .$is resu%t e%iminate

    t$e conservative moe%0 secon rep%ication prouce &ot$ %ig$t an $)&ri *+, a resu%t t$at e%iminatet$e ispersive moe% an supporte t$e semiconservative moe%0

    First repli(atio- Se(o-d repli(atio-

    Co-ser;ati;e

    5odel

    Se5i(o-ser;ati;e

    5odel

    %ispersi;e

    5odel

    DNA R li i A Cl & '

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    DNA Re!lication:A Closer &oo'

    .$e cop)ing of *+

    # Is remar#a&%e in its spee an accurac)

    =ore t$an a oBen enB)mes an ot$er proteins

    # Participate in *+ rep%ication

    $ i S d ) i i f R li i

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    $ettin# Started( )ri#ins of Replication

    .$e rep%ication of a *+ mo%ecu%e

    # 6egins at specia% sites ca%%e origins ofrep%ication, w$ere t$e two strans are

    separate

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    eu#ar)otic c$romosome

    # =a) $ave $unres or even t$ousans ofrep%ication origins

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    A ti ll l El ti

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    Antiparallel Elon#ation

    -ow oes t$e antipara%%e% structure of t$e

    ou&%e $e%i( affect rep%icationF

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    *+ po%)merases a nuc%eoties

    # On%) to t$e free 3 en of a growing stran

    %ong one temp%ate stran of *+, t$e %eaing

    stran

    # *+ po%)merase III can s)nt$esiBe a

    comp%ementar) stran continuous%), moving

    towar t$e rep%ication for#

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    .o e%ongate t$e ot$er new stran of *+, t$e

    %agging stran

    # *+ po%)merase III must wor# in t$e irection

    awa) from t$e rep%ication for#

    .$e %agging stran

    # Is s)nt$esiBe as a series of segments ca%%e

    O#aBa#i fragments, w$ic$ are t$en 4oine

    toget$er &) *+ %igase

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    Pare-tal %N&

    *+ po% I%% e%ongates

    *+ strans on%) in t$e

    5 3irection0

    1

    O#aBa#i

    fragments

    *+ po% III

    .emp%ate

    stran

    Lagging stran3

    2

    .emp%ate

    stran *+ %igase

    Overa%% irection of rep%ication

    One new stran, t$e %eaing stran,

    can e%ongate continuous%) 5 3

    as t$e rep%ication for# progresses0

    !

    .$e ot$er new stran, t$e

    %agging stran must grow in an overa%%

    3 5irection &) aition of s$ort

    segments, O#aBa#i fragments, t$at grow

    5 3num&ere $ere in t$e orer

    t$e) were mae;0

    "

    *+ %igase 4oins O#aBa#ifragments &) forming a &on &etween

    t$eir free ens0 .$is resu%ts in a

    continuous stran0

    *

    Figure 16.1*

    35

    5

    3

    3

    5

    21

    Leaing stran

    1

    8)nt$esis of %eaing an %agging strans uring

    *+ rep%ication

    "rimin# DNA Synthesis

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    "rimin# DNA Synthesis

    *+ po%)merases cannot initiate t$e s)nt$esis

    of a po%)nuc%eotie

    # .$e) can on%) a nuc%eoties to t$e 3en

    .$e initia% nuc%eotie stran

    # Is an

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    Overa%% irection of rep%ication

    3

    3

    3

    3

    5

    35

    35

    3

    5

    3

    5

    3

    5

    3

    5

    3 5

    5

    1

    1

    21

    12

    5

    5

    12

    35

    .emp%ate

    stran

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    )ther "roteins That Assist DNA Replication

    -e%icase, topoisomerase, sing%e'stran &ining

    protein

    # re a%% proteins t$at assist *+ rep%ication

    Ta$le 16.1

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    Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsFigure 16.16

    Overa%% irection of rep%icationLeaing

    stran

    Lagging

    stran

    Lagging

    stran

    Leaing

    stranO>IW

    Leaing

    stran

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    The DNA Replication %achine as a Stationary Comple+

    .$e various proteins t$at participate in *+

    rep%ication

    # !orm a sing%e %arge comp%e(, a *+

    rep%ication 7mac$ine

    .$e *+ rep%ication mac$ine

    # Is pro&a&%) stationar) uring t$e rep%ication

    process

    roofreading and Re!airing DNA

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    roofreading and Re!airing DNA

    *+ po%)merases proofrea new%) mae *+

    #

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    Figure 16.13

    +uc%ease

    *+

    po%)merase

    *+

    %igase

    t$)mine imer

    istorts t$e *+ mo%ecu%e0

    1

    nuc%ease enB)me cuts

    t$e amage *+ stran

    at two points an t$eamage section is

    remove0

    !

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    Re!licating the "nds of DNA Molecules

    .$e ens of eu#ar)otic c$romosoma% *+

    # et s$orter wit$ eac$ roun of rep%ication

    Figure 16.17

    n of parenta%

    *+ strans

    Leaing stran

    Lagging stran

    Last fragment Previous fragment

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    u#ar)otic c$romosoma% *+ mo%ecu%es

    # -ave at t$eir ens nuc%eotie se?uences,ca%%e te%omeres, t$at postpone t$e erosion of

    genes near t$e ens of *+ mo%ecu%es

    Figure 16.18 1 Em

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    If t$e c$romosomes of germ ce%%s &ecame

    s$orter in ever) ce%% c)c%e

    # ssentia% genes wou% eventua%%) &e missing

    from t$e gametes t$e) prouce

    n enB)me ca%%e te%omerase

    # "ata%)Bes t$e %engt$ening of te%omeres in

    germ ce%%s