Chapterf1f-fDNAfstructurefandffunction
● Checkfobjectivesfatfthefendf
Whatfisfgenetics
● Geneticsfisfthefstudyfoffthefgeneralfmechanismsfoffheredityfandfthefvariationfoffinheritedftrai
ts
○ AllfcellsfcontainfDNAflocatedfinfthefnucleusfoffthefcellf(exceptfmaturefRBC)
○ DNAfcontainsfthefinstructionsfforfeveryfproteinfthatfisfmadefbyfthefbody
■ OurfDNAfisfwhatfmakesfeachfoffusfunique
○ EachfpersonfhasfuniquefDNAf(unlessfyou’refanfidenticalftwin)
● Genomicsfisfthefstudyfofftheffunctionfoffthefnucleotidefsequencesfpresentfinfthefgenome
○ Whichfproteinsfandfwhichfversionsfarefexpressedfinfeachfcell
● WhatfdoesfDNAfreallyfdo?
○ Itfisfthefinstructionsftofmakefeveryfproteinfinfthefbody
■ Itfisfthefblueprintfforfthefbody
○ Eachfcellfhasfthefinstructionsftofmakefthesefproteins
● Infthefnucleusfoffthefcell,fDNAfisforganizedfintofchromosomes
○ Chromosomesf-
faftemporaryfstructurefthatfisfaflargefchunkfoffDNAfcontainingfmanyfgenes
■ Eachfchromosomesfcontainsfmanyfgenes
● Humanfgenomefisf3.2fbillionfnucleotidesflong
● Eachfpersonfhasf23fpairsfoffchromosomes
○ Genef-
fspecificfsegmentfoffDNAfthatfcontainsfthefgeneticfcodefforfafspecificfprotein
○ Duplicatedfchromosomefisftheftypicalfshapefwefthinkfchromosomesftofbe.fthesefare
fsisterfchromatidsfheldftogetherfbyfafcentromere
■ AfchromosomefisfjustfthefonefsidefT
hefstructurefoffDNA
● Infthefnucleusfoffthefcell,fDNAfisforganizedfintofchromosomes
● Genesfareforganizedfintofchromosomes
● Humansfhavef23fpairsfoffchromosomes,f2fcopiesfoffeach
, ● Thefchromosomesfhavefafpfarmfandfafqfarm,fwhichfindicatesfthefpositionfoffthefchr
omosome
○ Pfarmfgoesf11.1-15.5
○ Qfarmfgoesf11-25
● Telomerefisfthefrepeatfzonefwherefeverythingfgetsfrepeated.fIt’sfthefcapfoffthefchr
omosome
● DNAfisfcomposedfoffsubunitsfcalledfnucleotides
● Nucleotidesfarefmadefupfoff3fcomponents:fafnitrogenfbase,fafdeoxyribosefsugar,fandfafpho
sphate
● Therefareffourfdifferentfnitrogenfbases:
○ Adeninef-fpurine;fdoublefringfstructure
○ Thyminef-fpyrimidines;fsinglefring
○ Guaninef-fpurine;fdoublefringfstructure
○ Cytosinef-fpyrimidines;fsinglefring
● Nucleotidesfjoinftogetherfinfaflineftofformfafstrand
● Twofstrandsfjoinftogetherfwithfcompatiblefnitrogenfbasesfbondingfinfthefmiddle
● Adeninefbindsfwithfthymine
● Guaninefbindsfcytosine
● ThefsequencefoffthefnitrogenfbasesfalongfafstrandfisfthefDNAfsequence
○ Singlefstrandf=fsugar,fphosphate,fandfbases
■ Backbonef=fconnectedfalongfthefstrand
■ Anti-parallelf=fwhenfbasefisfinsidefandfsugarfisfoutside
■ WefreadfupfonefsidefoffDNAfbecausefoffthefpairingfpatterns
● Complimentfisfwhatfthefotherfsidefoffthefstrandfis
● ThefDNAfmoleculefisfsimilarftofafladder
● Thefmatchedfnitrogenfbasesfarefthefrungsfoffthefladder
● ThefDNAfmoleculeftwistsftofformfafdoublefhelix
● Becausefoffcomplementaryfpairs,fiffthefsequencefoffonefstrandfisfknown,fthefsequencefoffthef
oppositefstrandfcanfbefpredictedfaccurately
CellfdivisionfandfDNAfreplication
● Cellsfdividefbyfmitosisfandfcytokinesisftofmakeftwofidenticalfdaughterfcells
, ○ SofthatftheyfcanfgetfallfoffthefDNAftofmakefthefappropriatefproteins
● Thisfprocessfoccursfinfseveralfsteps,fknownfasfthefcellfcycle
● G1f-fcellftakesfonfnutrientsfandfgrows
○ Functionsfinfthefwayfthatfthefcellfisfdesignedftoffunction
● Sf-fDNAfreplication
○ Notfallfcellsfreplicate,fmanyfcellsfdofnot
○ Synthesis
● G2f-fproductionfoffproteinsfimportantfforfcellfdivision
○ Preparationfforfcellfdivision
○ Nowfthefcellfcanfenterfintofmitosis
● Mf-fMitosis,factualfcellfdivisionfwithfnuclearfseparationffollowedfbyfcellfseparation
○ PMAT
■ Prophase,fmetaphase,fanaphase,ftelophase
○ Secondfhalffoffthefcellfdivision
● Cytokinesisf-fdivisionfoffthefcytoplasm
○ Afterftelophase
● Whenfafcellfdivides,fthefDNAffirstfundergoesfreplication,fwhichfresultsfinftwofidenticalfsets
foffDNA
● Eachfnewfcellfcreatedfmustfhavefafcompletefgenome
● ThefDNAfoffthefparentfcellfmustfreplicatefexactly
● Withfnormalfcellfdivision,fthefparentfcellfdividesfcorrectly,fandfeachfnewfcellfhasfthefide
nticalfandfcorrectfamountfoffDNAfandfgenes
● Newfcomplementaryfstrandsfarefsynthesizedfalongfthefoldfstrands,fusingfthefoldfstrandsfasft
emplatesftofplacefeachfnewfcomplementary
● Eachfnewfsetfoffds-DNAfcontainsfonefstrandfofforiginalfds-
DNAfandfonefnewlyfsynthesizedfstrand
● Becausefeachfofftheftwofnewfsetsfoffds-
DNAfcontainsfonefofftheforiginalfstrands,fthisftypefoffDNAfsynthesisfisfknownfasfthefsem
i-conservativefmodelfoffDNAfreplication
● OncefDNAfhasfbeenfreplicated,fthefchromosomesfbecomefsisterfchromatids
● Thefcellfcanfdividefusingfmitosisfandfcytokinesis
, ● Duringfmitosis,fthefduplicatedfchromosomesfseparateftofensurefthatfeachfdaughterfcellfget
sfonefcopyfoffeachfchromosome
● Thefdaughterfcellsfarefgeneticallyfidenticalftofeachfotherfandfthefparentfcells
○ Interphasef-fpreambleftofmitosisf(G1,fS,fG2)
○ Prophasef-
fthickeningfoffsisterfchromatids,fdissolvingfoffnuclearfmembrane,fformationfoff
mitoticfspindlef(helpsforganizefchromosomesftofensurefthey’refformedfproperl
y)
○ Prometaphasef-
flossfoffnuclearfenvelopefsofnuclearfmembranefisfdissolvedfandfspindlefisfattachedf
tofkinetochore
○ Metaphasef-fsisterfchromatidsflinefupftofthefmiddlefoffthefcell
■ Thefspindlefmustfbefattachedftofbothfsidesfoffthefchromatidsforfelsefthefdau
ghterfcellfwillfendfupfwithfoneflessforfonefmore
○ Anaphasef-
fseparatesfchromosomesftofensurefthefdaughterfcellsfendfupfwithfrightfamountfoffchr
omosomes
○ Telophasef-fformationfofftwofseparatefnucleif(bothfwithf46fchromosomes)
○ Cytokinesisf-
cellsfpinchfapartfandfseparate.fIdenticalftofeachfotherfandfparentfcellfChromosomes
f
● Geneticfanalysisfstartsfwithfcountingfthefchromosomesfinfonefcellftofdeterminefhowfma
nyfchromosomesfarefpresent
● Thenfchromosomesfareforganizedfintofpairsfandfthenfarrangedfintofafkaryotype
● Thefpairsfarefarrangedfandfnumberedfbyfsizef(largestftofsmallest)fandfcentromerefposition
● Theffirstf22fchromosomesfarefthefautosomesf(nonfsexfchromosomes),fandftheflastftwofarefthef
sexfchromosomes,fXXforfXYf(femaleforfmale)
● Eachfpersonfgetsfoncefcopyfoffeachfchromosomeffromfeachfparent
● Thefgenesfonfchromosomesfcodefforfthefsamefprotein,fbutfhavefsomefsequencefdif
ferencesfdueftofmutation
● Differentfformsfoffthefsamefgenefarefcalledfalleles
● Genotypef-fthefexactfallelefpairfcompositionfpresent
● Phenotypef-fthefobservedfexpressionfoffanyfgivenfsingle-geneftrait
● Dominantftrait
● Checkfobjectivesfatfthefendf
Whatfisfgenetics
● Geneticsfisfthefstudyfoffthefgeneralfmechanismsfoffheredityfandfthefvariationfoffinheritedftrai
ts
○ AllfcellsfcontainfDNAflocatedfinfthefnucleusfoffthefcellf(exceptfmaturefRBC)
○ DNAfcontainsfthefinstructionsfforfeveryfproteinfthatfisfmadefbyfthefbody
■ OurfDNAfisfwhatfmakesfeachfoffusfunique
○ EachfpersonfhasfuniquefDNAf(unlessfyou’refanfidenticalftwin)
● Genomicsfisfthefstudyfofftheffunctionfoffthefnucleotidefsequencesfpresentfinfthefgenome
○ Whichfproteinsfandfwhichfversionsfarefexpressedfinfeachfcell
● WhatfdoesfDNAfreallyfdo?
○ Itfisfthefinstructionsftofmakefeveryfproteinfinfthefbody
■ Itfisfthefblueprintfforfthefbody
○ Eachfcellfhasfthefinstructionsftofmakefthesefproteins
● Infthefnucleusfoffthefcell,fDNAfisforganizedfintofchromosomes
○ Chromosomesf-
faftemporaryfstructurefthatfisfaflargefchunkfoffDNAfcontainingfmanyfgenes
■ Eachfchromosomesfcontainsfmanyfgenes
● Humanfgenomefisf3.2fbillionfnucleotidesflong
● Eachfpersonfhasf23fpairsfoffchromosomes
○ Genef-
fspecificfsegmentfoffDNAfthatfcontainsfthefgeneticfcodefforfafspecificfprotein
○ Duplicatedfchromosomefisftheftypicalfshapefwefthinkfchromosomesftofbe.fthesefare
fsisterfchromatidsfheldftogetherfbyfafcentromere
■ AfchromosomefisfjustfthefonefsidefT
hefstructurefoffDNA
● Infthefnucleusfoffthefcell,fDNAfisforganizedfintofchromosomes
● Genesfareforganizedfintofchromosomes
● Humansfhavef23fpairsfoffchromosomes,f2fcopiesfoffeach
, ● Thefchromosomesfhavefafpfarmfandfafqfarm,fwhichfindicatesfthefpositionfoffthefchr
omosome
○ Pfarmfgoesf11.1-15.5
○ Qfarmfgoesf11-25
● Telomerefisfthefrepeatfzonefwherefeverythingfgetsfrepeated.fIt’sfthefcapfoffthefchr
omosome
● DNAfisfcomposedfoffsubunitsfcalledfnucleotides
● Nucleotidesfarefmadefupfoff3fcomponents:fafnitrogenfbase,fafdeoxyribosefsugar,fandfafpho
sphate
● Therefareffourfdifferentfnitrogenfbases:
○ Adeninef-fpurine;fdoublefringfstructure
○ Thyminef-fpyrimidines;fsinglefring
○ Guaninef-fpurine;fdoublefringfstructure
○ Cytosinef-fpyrimidines;fsinglefring
● Nucleotidesfjoinftogetherfinfaflineftofformfafstrand
● Twofstrandsfjoinftogetherfwithfcompatiblefnitrogenfbasesfbondingfinfthefmiddle
● Adeninefbindsfwithfthymine
● Guaninefbindsfcytosine
● ThefsequencefoffthefnitrogenfbasesfalongfafstrandfisfthefDNAfsequence
○ Singlefstrandf=fsugar,fphosphate,fandfbases
■ Backbonef=fconnectedfalongfthefstrand
■ Anti-parallelf=fwhenfbasefisfinsidefandfsugarfisfoutside
■ WefreadfupfonefsidefoffDNAfbecausefoffthefpairingfpatterns
● Complimentfisfwhatfthefotherfsidefoffthefstrandfis
● ThefDNAfmoleculefisfsimilarftofafladder
● Thefmatchedfnitrogenfbasesfarefthefrungsfoffthefladder
● ThefDNAfmoleculeftwistsftofformfafdoublefhelix
● Becausefoffcomplementaryfpairs,fiffthefsequencefoffonefstrandfisfknown,fthefsequencefoffthef
oppositefstrandfcanfbefpredictedfaccurately
CellfdivisionfandfDNAfreplication
● Cellsfdividefbyfmitosisfandfcytokinesisftofmakeftwofidenticalfdaughterfcells
, ○ SofthatftheyfcanfgetfallfoffthefDNAftofmakefthefappropriatefproteins
● Thisfprocessfoccursfinfseveralfsteps,fknownfasfthefcellfcycle
● G1f-fcellftakesfonfnutrientsfandfgrows
○ Functionsfinfthefwayfthatfthefcellfisfdesignedftoffunction
● Sf-fDNAfreplication
○ Notfallfcellsfreplicate,fmanyfcellsfdofnot
○ Synthesis
● G2f-fproductionfoffproteinsfimportantfforfcellfdivision
○ Preparationfforfcellfdivision
○ Nowfthefcellfcanfenterfintofmitosis
● Mf-fMitosis,factualfcellfdivisionfwithfnuclearfseparationffollowedfbyfcellfseparation
○ PMAT
■ Prophase,fmetaphase,fanaphase,ftelophase
○ Secondfhalffoffthefcellfdivision
● Cytokinesisf-fdivisionfoffthefcytoplasm
○ Afterftelophase
● Whenfafcellfdivides,fthefDNAffirstfundergoesfreplication,fwhichfresultsfinftwofidenticalfsets
foffDNA
● Eachfnewfcellfcreatedfmustfhavefafcompletefgenome
● ThefDNAfoffthefparentfcellfmustfreplicatefexactly
● Withfnormalfcellfdivision,fthefparentfcellfdividesfcorrectly,fandfeachfnewfcellfhasfthefide
nticalfandfcorrectfamountfoffDNAfandfgenes
● Newfcomplementaryfstrandsfarefsynthesizedfalongfthefoldfstrands,fusingfthefoldfstrandsfasft
emplatesftofplacefeachfnewfcomplementary
● Eachfnewfsetfoffds-DNAfcontainsfonefstrandfofforiginalfds-
DNAfandfonefnewlyfsynthesizedfstrand
● Becausefeachfofftheftwofnewfsetsfoffds-
DNAfcontainsfonefofftheforiginalfstrands,fthisftypefoffDNAfsynthesisfisfknownfasfthefsem
i-conservativefmodelfoffDNAfreplication
● OncefDNAfhasfbeenfreplicated,fthefchromosomesfbecomefsisterfchromatids
● Thefcellfcanfdividefusingfmitosisfandfcytokinesis
, ● Duringfmitosis,fthefduplicatedfchromosomesfseparateftofensurefthatfeachfdaughterfcellfget
sfonefcopyfoffeachfchromosome
● Thefdaughterfcellsfarefgeneticallyfidenticalftofeachfotherfandfthefparentfcells
○ Interphasef-fpreambleftofmitosisf(G1,fS,fG2)
○ Prophasef-
fthickeningfoffsisterfchromatids,fdissolvingfoffnuclearfmembrane,fformationfoff
mitoticfspindlef(helpsforganizefchromosomesftofensurefthey’refformedfproperl
y)
○ Prometaphasef-
flossfoffnuclearfenvelopefsofnuclearfmembranefisfdissolvedfandfspindlefisfattachedf
tofkinetochore
○ Metaphasef-fsisterfchromatidsflinefupftofthefmiddlefoffthefcell
■ Thefspindlefmustfbefattachedftofbothfsidesfoffthefchromatidsforfelsefthefdau
ghterfcellfwillfendfupfwithfoneflessforfonefmore
○ Anaphasef-
fseparatesfchromosomesftofensurefthefdaughterfcellsfendfupfwithfrightfamountfoffchr
omosomes
○ Telophasef-fformationfofftwofseparatefnucleif(bothfwithf46fchromosomes)
○ Cytokinesisf-
cellsfpinchfapartfandfseparate.fIdenticalftofeachfotherfandfparentfcellfChromosomes
f
● Geneticfanalysisfstartsfwithfcountingfthefchromosomesfinfonefcellftofdeterminefhowfma
nyfchromosomesfarefpresent
● Thenfchromosomesfareforganizedfintofpairsfandfthenfarrangedfintofafkaryotype
● Thefpairsfarefarrangedfandfnumberedfbyfsizef(largestftofsmallest)fandfcentromerefposition
● Theffirstf22fchromosomesfarefthefautosomesf(nonfsexfchromosomes),fandftheflastftwofarefthef
sexfchromosomes,fXXforfXYf(femaleforfmale)
● Eachfpersonfgetsfoncefcopyfoffeachfchromosomeffromfeachfparent
● Thefgenesfonfchromosomesfcodefforfthefsamefprotein,fbutfhavefsomefsequencefdif
ferencesfdueftofmutation
● Differentfformsfoffthefsamefgenefarefcalledfalleles
● Genotypef-fthefexactfallelefpairfcompositionfpresent
● Phenotypef-fthefobservedfexpressionfoffanyfgivenfsingle-geneftrait
● Dominantftrait
