Understanding how our genes are passed down And … · And how to calculate the probabilities of...
Transcript of Understanding how our genes are passed down And … · And how to calculate the probabilities of...
![Page 1: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/1.jpg)
Unit3:GeneticsCalculatingthe
probabilityofourgenetics
UnderstandinghowourgenesarepasseddownAndhowtocalculatetheprobabilitiesofourtraits.
![Page 2: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/2.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
Leading questions:
1. What do Punnett Squares mean?
2. How do we calculate the probabilities of our traits?
3. What traits will pass down and by how much?
![Page 3: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/3.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
Do you remember these?
![Page 4: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/4.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
What do the y and Y represent and where are they from?
![Page 5: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/5.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
Recall from meiosis
• A pair of homologous chromosomes (chromosomes of similar traits) are crossed over and separated.
• The gene that results in the sex cells are the “letters” from Punnett Squares.
![Page 6: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/6.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
What does that mean?If the red chromosome containsthe genes for Brown eyes (B).
If yellow contains genes for Blueeyes (b)
After crossing over, the genesswitch chromosomes with theother.
bB
bb
B
B
Sisterchromatids
![Page 7: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/7.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
What does that mean?• At the end of
meiosis, all 4 ofthese sisterchromatids willseparate (segregate) into 4 sex cells.
• Because theprobability of gettingB and b is the same, that is why we useBb!
bb
B
B
B
bb
bB
![Page 8: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/8.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
When the genes ofthe homologouschromosomesseparate into separatesex cells, Mendelclassified this as the“Law of Segregation”.
Thiswillresultinasexcellwithtraitsthatareeitherfromyourmom(browneyes)ordad(blueeyes).
![Page 9: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/9.jpg)
Weusesymbolstorepresentdominantandrecessivegenes.• Thedominantgene isalwaysrepresentedbyacapitalletter.
• E.g.A
• Therecessivegeneisalwaysrepresentedbythesameletterinthelowercase.
• E.g.a
Towritethecombinationofatrait,twolettersmustbeused.Ie.AA,aa,Aa
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
![Page 10: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/10.jpg)
Example
Brownhairisadominantgene
Blondehairisarecessivegene
Brownhair’sgenewillbeexpressed becauseitisthedominant gene
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
![Page 11: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/11.jpg)
Otherimportantterms• Alleles - Alternativeformsofageneforagiventrait(Bluevsbrowneyes)
• Genotype – theallelespossessedbyanindividualforaspecifictrait.
• Eg:BB,Bb,andbbarepossiblegenotypesforeyecolour.
• 2copiesofdominantallele=homozygousdominantgenotype(BB).
• 2copiesofrecessiveallele=homozygousrecessivegenotype (bb).
• 1copyofeach=heterozygous genotype(Bb).
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
![Page 12: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/12.jpg)
• Phenotype – thephysicalappearanceofatrait(ie:whatthegenesactually“do”tous).
• Ex.Blueeyes,short,longtoenails,Extrahormones.
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
Pforphysicaltraits!
![Page 13: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/13.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
Howdowecalculatetheprobabilityofourgenes?
![Page 14: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/14.jpg)
Monohybrid Crosses• Across(combinationofalleles) foronetrait =amonohybridcross.
• Eg:Ifaheterozygouswomanwithawidow’speakreproduceswithaman withthesame genotype,whatkindofhairlinewilltheirchildrenhave?
• (Note:widow’speakisdominant overstraighthairline).
Unit3:GeneticsMonohybridcrosses
![Page 15: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/15.jpg)
• Youmayalsobeaskedtodeterminegenotypicratiosandphenotypicratios intheoffspring:
Genotypicratios:1WW:2Ww :1ww (or,moresimply,1:2:1)
Phenotypicratios:3widow’speak:1straighthairline(3:1)
**Phenotypicratioscanalsobewrittenaspercentages:25%chanceofstraighthairline75%chanceofwidow’speak
Unit3:GeneticsMonohybridcrosses
W w
W WW Ww
w Ww ww
![Page 16: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/16.jpg)
Whatifsomeoneshowsthedominantphenotype,butwedonotknowiftheyarehomozygousdominant orheterozygous?• Wecandoatestcross:
• Crosstheindividualwiththeunknowngenotypewithonethatishomozygousrecessive.
• Whyhomozygousrecessive?
Unit3:GeneticsTestcross
![Page 17: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/17.jpg)
Example:Akidhasbrowneyes(dominanttrait)butwedon’tknowifheisheterozygousorhomozygousdominant.Howcanwedeterminehisgenotype?
Unit3:GeneticsTestcross
B bb Bb bbb Bb bb
Kid’sgenotype
B Bb Bb Bbb Bb Bb
Kid’sgenotype
UseatestcrossThekid’sgenotypecouldbe2possibilities.IfALLoftheoffspringinthetestcrossshowthedominanttrait,thenthekid’sgenotypeishomozygousdominant.
![Page 18: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/18.jpg)
InBorderCollies,blackcoat(B)isdominant toredcoat(b). Abreederhasablackmale thathaswonnumerousawards. ThebreederwouldliketousethedogforbreedingifheispurebredorBB. Tolearnthisinformation,shetestcrosseshimwitharedfemale(bb).
Unit3:GeneticsTestcross
1.Iftheblackmaleis BB,whatkindofgamete(sperm)canheproduce?
2.Iftheredfemaleis bb,whatkindofgamete(eggs)cansheproduce?
B
b
![Page 19: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/19.jpg)
InBorderCollies,blackcoat(B)isdominant toredcoat(b). Abreederhasablackmale thathaswonnumerousawards. ThebreederwouldliketousethedogforbreedingifheispurebredorBB. Tolearnthisinformation,shetestcrosseshimwitharedfemale(bb).
Unit3:GeneticsTestcross
2.Ifanyofthepuppiesarered,whatisthefather'sgenotype?
Blackmalecouldbe:
BBorBb
Testwithbb
![Page 20: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/20.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
Trysomequestionsnow!
![Page 21: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/21.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
PunnettSquareswithBloodtypes• Thereare4mainbloodtypesin
humans:A,B,AB,andO
• BloodtypeAandBaredominant,TypeOisrecessive.
• WeuseIA toindicateadominantAallelegeneandIBforalleleBblood.
• iirepresentsrecessiveforOblood.
![Page 22: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/22.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
PunnettSquareswithBloodtypes
• InordertogettypeABblood,bothdominant allelesofAandBmustbeexpressedtogether.Theyareco-dominant(seelater).
• Ex.IAIB
![Page 23: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/23.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
BloodtypeExample• CouldamanwithtypeBbloodandawomanwithtype
ABproduceachildwithtypeOblood?
• 2possibilitiesfortypeBblood:IBIB orIBi
![Page 24: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/24.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
BloodtypeExample• CouldamanwithtypeBbloodandawomanwithtype
ABproduceachildwithtypeOblood?
• Sincethere’snohomozygousrecessive(ii),TypeObloodisnotpossible.
![Page 25: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/25.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
BloodtypeExample1.WhatifthemotheristypeOandthefatherisA?Whatwouldtheoffspring'sbloodtypebe?
![Page 26: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/26.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
BloodtypeExample2. A woman with Type O blood and a man who is Type AB have are expecting a child. What are the possible blood types of the kid?
![Page 27: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/27.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
Sex-linkedproblemswithPunnettSquares• Traitscontrolledbygenesonthesexchromosomesare
calledsex-linkedtraits.• WeusuallyfocusontraitscontrolledbytheX
chromosome• ThisisbecauseithasmanymoregenesthantheY
chromosome!
![Page 28: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/28.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
Sex-linkedproblemswithPunnettSquares• Notationforsex-linkedgenes:• GenescarriedontheXchromosome:
• UsetheletterXtoindicatethatthegeneisontheXchromosome
• Useasuperscript letterforthetraititself.• Eg:XB =dominantgenefornormalcolourvision
Xb =recessivegeneforcolour-blindness
![Page 29: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/29.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
Sex-linkedproblemswithPunnettSquaresExamples:Red-greencolour-blindness(X-linked)
XB =normal;Xb =colour-blind
Genotype Phenotype
XBXB Female; normalvision
XBXb Female;normalvision(carrier)
XbXb Female; colourblind
XBY Male;normalvision
XbY Male;colourblind
Noticehowthegenotypesarewrittenandwhatthephenotypesare!
![Page 30: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/30.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
Sex-linkedproblemswithPunnettSquares• Note:Becausemalesonlyhaveone Xchromosome,
theycannotbecarriers ofsex-linkeddisordersorconditions.
• Theyeitherhavethegeneandshowthecondition,ordon’thaveitanddon’tshowthecondition.
Genotype Phenotype
XBXB Female; normalvision
XBXb Female;normalvision(carrier)
XbXb Female; colourblind
XBY Male;normalvision
XbY Male;colourblind
Cannotbeacarrier!!!
![Page 31: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/31.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
Sex-linkedproblemswithPunnettSquaresExamplescont’d:• Hemophilia(deficiency
inbloodclottingfactors)• Duchennemuscular
dystrophy• (Theseareallrecessive
conditions)
![Page 32: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/32.jpg)
Sex-LinkedInheritancePracticeProblems• Boththemotherandthefatherofacolorblindmaleappeartobenormal.Colourblindness isrecessive.Fromwhomdidthesoninheritthealleleforcolorblindness?Whatarethegenotypesofthemother,father,andtheson?
![Page 33: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/33.jpg)
Sex-LinkedInheritancePracticeProblems• Awomaniscolorblind.Whatarethechancesthathersonwillbecolorblind?Ifsheismarriedtoamanwithnormalvision,whatarethechancesthatherdaughterswillbecolorblind?Willbecarriers?
![Page 34: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/34.jpg)
Sex-LinkedInheritancePracticeProblems• Boththehusbandandthewifehavenormalvision.Thewifegivesbirthtoacolorblinddaughter.Isitmorelikelythefatherhadnormalvisionorwascolorblind?Whatdoesthisleadyoutodeduceaboutthegirl’sparentage?
![Page 35: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/35.jpg)
Sex-LinkedInheritancePracticeProblems• Whatisthegenotypeofacolorblindmalewithlongfingersiss=longfingers?Ifallhischildrenhavenormalvisionandshortfingers,whatisthelikelygenotypeofthemother?
![Page 36: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/36.jpg)
Unit3:GeneticsTracingx-linkedwithpedigree
PedigreeCharts!
PedigreeChartstrackingx-linkeddisorders
![Page 37: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/37.jpg)
Unit3:GeneticsTracingx-linkedwithpedigree
PedigreeCharts!Mydog’sPurebredPedigree:http://www.k9data.com/pedigree.asp?ID=116679
Pedigreechartstracksthegenetictraitsovergenerationssimilartoafamilytree.
SquaresindicateMALE
CirclesindicateFEMALES
![Page 38: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/38.jpg)
Unit3:GeneticsTracingx-linkedwithpedigree
Example1:Leopold’sfamily(QueenVictoria’sson)
(a)Whatistheprobabilitythatherothersonwashemophilic?
(b)Whatistheprobabilitythatherdaughterwasacarrier?Hemophilic?
(c)Whatistheprobabilitythatbothchildrenwerenormal?
![Page 39: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/39.jpg)
Unit3:GeneticsTracingx-linkedwithpedigree
Example1:Victoria’syoungestdaughterBeatrice’sfamily
(a)Lookingatthepedigreeoftheroyalfamily,identifywhichofBeatrice’schildrenreceivedthehemophilicgene;whycanyoumakethisconclusion?
(b)NoticethatBeatrice’sdaughter,Eugenie,marriedKingAlfonsoXIIIofSpainandhadsixchildren,oneofwhomwasthefatherofJuanCarlos,thecurrentKingofSpain.WouldyoupredictthatJuanCarloswasnormal,acarrier,orahemophilic?
![Page 40: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/40.jpg)
Unit3:GeneticsTracingx-linkedwithpedigree
DrawingExample
Amanandwomanmarry.Theyhavefivechildren,2girlsand3boys.Themotherisacarrierofhemophilia,anX-linkeddisorder.Shepassesthegeneontotwooftheboyswhodiedinchildhoodandoneofthedaughtersisalsoacarrier.Bothdaughtersmarrymenwithouthemophiliaandhave3children(2boysandagirl).Thecarrierdaughterhasonesonwithhemophilia.Oneofthenon-carrierdaughter’ssonsmarriesawomanwhoisacarrierandtheyhavetwindaughters.
Whatisthepercentchancethateachdaughter(twins)willalsobeacarrier?
![Page 41: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/41.jpg)
Unit3:GeneticsDihybridCrosses
DihybridCrosses(2alleles)!
![Page 42: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/42.jpg)
Mendel’s2nd LawistheLawofIndependentAssortment:
• TheLawofIndependentAssortmentiswhenthereare2differenttraits onthehomologouschromosome(eyecolourandhaircolour)
• Eachofthesetraitswillindependently separate.
• Forexample:Bb(eyes)andHh (hair)willseparateintoBHBh Hb andhb.
• Theimportantpartisthatthetraitsdonot“sticktogether”
Unit3:GeneticsDihybridCrosses
![Page 43: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/43.jpg)
![Page 44: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/44.jpg)
Unit3:GeneticsDihybridCrosses
Thisleadsustodihybridcrosses
Trackingtheinheritanceof2alleles
![Page 45: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/45.jpg)
Ex.ApersonwhoisWwSs (widow’speakandshortfingers)andapersonwhoisalsoWwSs havechildren:
1. Figureoutthegametesforeachparent• WS,Ws,wS,andws forboth• PlacethesecombinationsontheedgesofaPunnettsquare
2. Figureoutthegenotypesoftheoffspring(useaPunnettsquare)
Unit3:GeneticsDihybridCrosses
![Page 46: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/46.jpg)
FromthePunnettsquare:• Phenotypicratio - 9widow’speak,shortfingers;
• 3widow’speak,longfingers;
• 3straighthairline,shortfingers;
• 1straighthairline,longfingers(9:3:3:1)
![Page 47: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/47.jpg)
Tocalculatethechancesofhavingtwotraits,youmustmultiply theprobabilitiesofhavingeachindividualtraitandreporttheresult.
• Eg:Fromthepreviousproblem,whatarethechancesofhavingachildwithshortfingers andawidow’speak?
• Chanceofshortfingers=¾• Chanceofwidow’speak=¾• Chanceofhavingboth=¾x¾=9/16
Unit3:GeneticsDihybridCrosses
![Page 48: Understanding how our genes are passed down And … · And how to calculate the probabilities of our ... • 2 copies of recessive allele = homozygous recessive genotype ... widow’s](https://reader031.fdocuments.net/reader031/viewer/2022022607/5b85ff987f8b9a2e3a8bfc67/html5/thumbnails/48.jpg)
Unit3:GeneticsCalculatingtheprobabilityofourgenetics
Trysomequestionsnow!