INHERITANCETopic3-2017

Year10Biology

TOPIC3–INHERITANCE

Thingstocover:1. ReviewofTopics1-4

2. Genes&alleles

3. Heterozygous&homozygous

4. Genotypes&phenotypes

5. Dominanttraits&recessivetraits

6. Autosomal&sex-linkedtraits

7. Mutations

8. Pedigrees

Worktodo:

1. Activity–JerrySpringerpunnetsquares

2. Trollphenotypes

3. Punnetsquares–monohybridandsex-linked

4. TextbookQs–Ch2.6–Q-1-3,6,7,8,9,13

5. TextbookQs–Ch2.7–Q-2,3,5,6,7,8,9,

6. TextbookQs–Ch2.8–Q-1,3,4,6,7,8,10,11

7. TextbookQs–Ch2.9-Q-1-5,10,11,12,14

Ideastoknow:

• Gene

• Allele

• ABObloodgrouping

• Homologouschromosomes

• Gametes

• Heterozygous

• Homozygous

• Dominant

• Recessive

• Basesubstitutionmutation

• Frameshiftmutation

• Insertion

• Deletion

• Genotype

• Phenotype

• Completedominance

• Co-dominance

• Carrier

• Punnettsquare

• Monohybridcross

• Pedigreechart

• Genderbiasinpedigrees

• Generationskippinginpedigrees

• Sexlinkage

• Haemophilia

• Colourblindness

REVIEW

Topic1• DNAiscomposedof____________________.

• Eachnucleotideconsistsof:

− A____________________sugar

− A____________________group

− A____________________base(_____types)

• Thenucleotidesformchains.Twochainstwisttoformthe____________________shapeof

theDNAmolecule.

• ChemicalbondsholdtheDNAmoleculetogether.Strong____________________bondshold

thenucleotidestogether,whileweak____________________bondsformbetweenthe

bases.

Topic2

• DNAiscoileduptightlytoform_______________

• Thereare_______________ofchromosomesineverycell.

• Mostoftheseare_______________,controllinggeneralcharacteristics.

• Onepairarethe_______________,controllingbothsexualandgeneralcharacteristics.

• Celldivisionisnecessaryfor____________________,____________________and

reproduction.

• Onetypeofcelldivision,____________________,isusedintheformationofnewbodycells.

Itisalsousedbyunicellularorganismsfor____________________reproduction.The

__________daughtercellsformedare____________________totheparentcellandhave

__________chromosomes.

• Theothertypeofcelldivision,____________________,isusedtoformsexcells.Another

namefortheproductsofthistypeofdivisionare____________________Thisprocesstakes

placeinthereproductiveorgans.The__________daughtercellsformedare

____________________totheparentcellandhave__________chromosomes.Theyarealso

____________________insize.

• Inorderforcelldivisiontooccur,theDNAmust____________________andthe

REVIEW

chromosomesmustdivideequallybetweenthecells.

• ____________________canoccurifthisdoesnothappencorrectly.Forexample,disorders

involvingadditionalormissing____________________.

• DownSyndromeisoneexample.Thisdisorderresultsfromthepresenceof

____________________Chromosome21.Thisiscalled____________________21.

•

VARIATION

ThepopulationoftheEarthismorethan6billionpeople,andnotwoindividuals(apartfromidenticaltwins)aregeneticallythesame.Why?

• Peoplearedifferentbecausethey________________________________________

____________________(or____________________)fromtheirparents.

• Childrencarrya____________________setof____________________;halffromtheir

motherandhalffromtheirfather.

• Aperson’suniquecharacteristicsarecausedby:

− the________________________________________theyinheritedfromtheir

parents(____________________)

− the________________________________________inwhichtheydeveloped

(____________________)

• Somecharacteristics,suchas____________________colourand____________________

shape,areonlydeterminedbygenes.Thesearecalled____________________

characteristics.

• Othertypesofcharacteristics,suchas____________________andhairlength,arenot

inheritedbutdependon________________________________________.Thesearecalled

____________________characteristics.

• Differencesinsomecharacteristicsareduetoa____________________ofbothinherited

andenvironmentalfactors.Insomecases,itcanbedifficulttosayhowmuchinfluenceeach

factorhas.

• Theoverallappearanceofanorganismdependson:

1. its____________________(inheritedcharacteristics)2. theeffectsofthe____________________inwhichitlives.

• Alltheobservablecharacteristicsofanorganismarecalledits____________________.

• Thefullsetofgenesofanorganismiscalledits____________________.

• Anorganism’sphenotypethereforedependsonits____________________plus________________________________________.

VARIATION

• ________________________________________isthemostimportantcauseof

________________________________________becauseitmixesupgeneticmaterial.

• During____________________,homologouschromosomes____________________

geneticmaterial.Theythenlineupandseparateindifferentways,

producingalarge____________________ofdifferent

____________________.

• At____________________,anymalegametecancombine

withanyfemalegamete.

• Alltheseeventsoccur____________________andcreate

new____________________ofgeneticmaterial.

• ____________________isthe____________________inthe____________________or____________________of____________________andisthereforeanothercauseofgeneticvariation.

• Mutationscanarise____________________;forexample,throughtheincorrectcopyingof

basepairsduringDNAreplication,orthe____________________distributionof

chromosomesduring________________________________________.

• Mutationscanalsobecausedby________________________________________,suchas

radiationandcertainchemicals.Thesefactorsarecalled____________________.

• Somemutationsmaybebeneficial,butmanyareharmfulandincreasetheriskofdiseases

suchas____________________.

GENES&ALLELES

• Thebasic____________________of____________________isthe____________________.• Ageneisasegmentofa____________________thatcontainsthe____________________

requiredtoproducea____________________.

• Thereare____________________ofeachchromosome,knownasa

________________________________________.Eachcopyhasitsown

____________________ofthegene.

• Theseversionsareknownas____________________.

• Mostgenesarecontrolledby____________________.

• Dominantalleles:− ____________________expressedinacell’s____________________

− only____________________ofthedominantalleleneedstobeinheritedinorderfor

ittobeexpressed

− representedbyan____________________caseletter(eg._______)

• Recessivealleles:− onlyexpressedinacell’sphenotypeif____________________arepresent

− ifonlyonecopyispresent,itseffectis‘____________________bythe

________________________________________

− representedbya____________________caseletter(eg._______)

• Iftheallelesforacharacteristicinahomologouspairarethe____________________,the

organismissaidtobe____________________forthatcharacteristic.

• Ifthereare____________________alleles,theorganismissaidtobe

________________________________________

forthatgene.

• Ifthereare____________________alleles,theorganismissaidtobe

________________________________________

forthatgene.

GENES&ALLELES

• Iftheallelesforacharacteristicinahomologouspair

are____________________,theorganismissaidto

be____________________forthatcharacteristic.

• Thecharacteristic____________________byheterozygousalleleswilldependonwhich

alleleis____________________andwhichalleleis____________________.

• Thealleleforbrowneyesis____________________overthealleleforblueeyes.• Theindividualwillhave____________________eyes,becausethealleleforbrowneyes

____________________thealleleforblueeyes.

TYPESOFINHERITANCE

COMPLETEDOMINANCE:ßNORMAL!!!!!• Ifthe____________________alleleispresent,itwillbe____________________

• eg.Browneyedallele(B)alwaysexpressedwhenpresent(BBorBb)

• Specialsymbols:

− Choose____________________

− Use____________________(recessive)and____________________(dominant)− eg.BB,bborBbß_______________________________________________________

CO-DOMINANCE:• Thereis________________________________________!

• Thephenotypeisa____________________ofbothallelespresent

• eg.redallele+whiteallele=____________________phenotype

• eg.____________________bloodfromcombinationofAandBalleles

• Specialsymbols:

− Choose____________________

− Use____________________forboth

− eg.RR,WWorRWß_____________________________________________________

ABOBLOODGROUPING

• Todetermineyourbloodtype,therearethreealleles:− A–____________________

− B-____________________

− O-____________________

• TheallelesIAandIBare____________________• However,bothoftheseallelesare________________________________________overί• Thisresultsin____________________differentphenotypes.

Phenotypeorbloodgroup

Genotypes

TypeA

TypeB

TypeAB

TypeO

TYPESOFINHERITANCE

AUTOSOMALINHERITANCE:ßNORMAL!!!!!• Thegeneinquestionislocatedonan____________________

• Traitscanbe:

− ________________________________________–meaningthatatrait/disorderis

determinedbythepresenceofadominantallele

− ________________________________________–determinedbythepresenceof

tworecessivealleles

• Specialsymbols:

− BB,bb,Bb

SEX-LINKEDINHERITANCE:• Thegeneinquestionislocatedona________________________________________

• Willgenerallybeonthe____________________,astheYcarriesveryfewgenes

• eg.____________________,________________________________________

• Traitscanbe:

− ________________________________________–meaningthatatrait/disorderis

determinedbythepresenceofthedominantalleleontheXchromosomes

− ________________________________________–meaningthatatrait/disorderis

determinedbythepresenceofoneortworecessiveallelesontheXchromosomes

• Specialsymbols:

− Females:

• Homozygous____________________ • Heterozygous__________

− Males(onlyoneXchromosome):

• Unaffected __________

• Affected __________

CARRIERS:• Someonewhois____________________foragenetic

disorder

• They____________________thedisorderthemselves

• However,thedisordercanbe____________________

tothenextgeneration

GENETICMUTATIONS

• Genesarenearlyalwayspassedfromparenttooffspring_____________________________.

• Occasionallya_________________willoccurinagene.

• Thisiscalleda__________________________________.

• __________________________________:

– onebaseis_________________foranother

• __________________________________:

– _________________

• insertionofoneormorebases

– _________________

• deletionofoneormorebases

• • Why?

– MutationinvolvesapartoftheDNAwhichthatparticularcell____________________

– Mutationoccursbutthecode

stillresultsinthesame__________________________________&thereforethesame_________________

• Generally,_________________mutationsaremoreserious.

PUNNETTSQUARES

• Alsocalled_________________ _________________

• Methodusedtofindthe_________________ genotypeandphenotyperatiosof_________________ whentheparentalgenotypesand/orphenotypesareknown.

• Steps:1. Writedownthe_________________ _________________

Youmayneedtochooselettertorepresentyourtrait

–chooseeasyoneslikeT,G,HnotC,S,Y

2. Writedownthe_________________ _________________ thattheyareabletopasson

intheirgametes(sexcells)3. ConstructthePunnettsquare

4. Fillinthe_________________ _________________ oftheoffspring

5. Determinethe_________________ _________________ oftheoffspring

6. Determinethe_________________ _________________ oftheoffspring

PUNNETTSQUARES

• Example:

Analienthatishomozygousdominantforgreenskinhaschosenanalienwhohaspurpleskinforhisbride.Determinethelikelihoodthattheirchildrenwillhavepurpleskin.

LikeinMaths–youneedtostatewhatsymbolsyouwillbeusingtorepresentyourtraits:

eg.LetG=green;g=purple

• Example:Oneofthecouplessons(Neyp)marriedafemalealienwhowashomozygousrecessiveforthe

skincolourtrait.

Workoutthegenotypeandphenotypepercentageoftheirpotentialoffspring.

PUNNETTSQUARES

• Example:

OneofNeyp’ssonsmarriedafemalealienwhowashomozygousforhaemophilia.

Calculatethelikelihoodthattheycouldhaveachildwithhaemophilia.

Again–specifyyoursymbols!

Itisasex-linkedrecessivedisorder!!!

So:LetH=_________________;h=_________________

PEDIGREECHARTS

• Showsthemembersofafamilyandhowtheyare_________________ toeachother.

• A___________________________________________________!

• Pedigreechartscanalsobeusedto_________________ the_________________ ofa_________________.

• Circles=_________________

• Squares=_________________

• Shading=_________________ individuals

• Parents=linkedbya_________________ line

• Children=_________________ linesrunningdownfromparents

• Siblings=linkedbya_________________ line_________________ them

PEDIGREECHARTS

• Example:DrawapedigreechartforNeypandhiswifeGjup.,includingtheirparentsandchildren.They

had3children,2boysandagirl.TheirdaughterHefghadpurpleskinandmarriedanalien

whoalsohadpurpleskin.Theyhadoneson–Yerg.TheirsonGuolhadgreenskinandwas

alsomarriedwithonepurpledaughter,Zcug.

Remember,beingpurpleistherecessivetrait!

• Pedigreechartscanalsobeusedtodetermineif:

– Thecharacteristicis_________________ or_________________.

– Thecharacteristicis_________________ or_________________.

• Thingstolookfor:

– Genderbiasofmales:females

– Affectedoffspringfromunaffectedparents

– Affectedsonsfromaffectedfathers

PEDIGREE–AFAMILYTREEMakeyourownfamilytreeforonetraitofyourchoosing(eyecolour,naturalhaircolour,orbloodtype).

Includeasmanypeopleonyourimmediatefamilyaspossibleandusealloftherulesforpedigrees.Identify

thenamesandgenotypesofallindividualsinyourpedigree.

AttachanswerstotextbookQstothebackofthebooklet