Act II Mission Memo Lab Instructions_ Scientific Reasoning: Analyzing Temperature and BiologicalBIO 181

Lab Instructions: Genetics and Evolution Act II Mission Memo
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Greetings Fellow Explorer: c c




The breeding experiment of sunstalks was a success! From this experiment, we learned that metal
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toleranceisindeedaheritabletrait.However,asisthecasewithmanytraits,metal tolerancein
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sunstalksisacontinuousvariablethatdependsonhundredsofgenes.
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Therefore,itwouldbeimpracticaltousegene-editingtoolstosavethepopulationsunstalks. c c c c c c c c c c c c c




Instead,weselectedsunstalkswithsufficientmetaltoleranceandtransplantedthemtothe
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contaminated areas of the sanctuary, hopefully giving the stalkleapers a chance for survival as well.
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Unfortunately,oursolutiontooneprobleminadvertentlycausedanotherproblem:oneof the c c c c c c c c c c c c




genesformetaltoleranceislinkedtoagenetraitthatenablestheazurepods’to
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responsetoachemicalstimulusfromthestalkleapers.Thesepodsmustclose properlyto
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protect the stalkleapers from their predators. Given that a single gene affects this function of the
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azurepods,wecaneditthisgenetocorrecttheprobleminrealtime,preventingthe collapse of an
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entire ecosystem.
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To save the sunstalks and the stalkleapers, we must apply ourunderstanding of genetics and evolution
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tothisproblem.Usethefollowingquestionstoguideyourwork:
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● Whatistheheritabilityofmetaltoleranceinthepopulationofsunstalks? c c c c c c c c




● Will the mean metal tolerance evolve rapidly enough for the population of
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stalkleaperstopersist? c c c




● Howshould we edit the DNAof asunstalktorestore itsabilityto close its azure pods?
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Universally in your debt, c c c




The AI c




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, Appendix 1 c




What is theheritabilityof metal tolerance inthepopulationofsunstalks?
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Beforeweresorttogeneediting,wemustbesurethatnaturalselectionwillenablethe sunstalksto
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adapttothecontaminatedsoilinthesanctuary.Therateatwhichatraitevolves by natural
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cselection depends on several factors, including the amount ofheritable variation in the
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trait. By estimating the heritability of metaltolerance, wecan get a step closer todetermininghow
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quicklythesunstalkscanadapttotheirenvironment.
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Wewillfollow twokeysteps to answer the question,“Whatis the heritability of metal tolerance c c c c c c c c c c c




in the population of sunstalks?”
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Step1:Interpretingheritability.Compare andinterpret estimatesofheritability
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traits.ThisstepwillprepareyoutoestimatetheheritabilityofmetaltoleranceinStep2.
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Step 2: Estimate the heritability of metal tolerance. Plot the linear relationship between the mean
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metaltoleranceofparentsandthemeanmetaltoleranceoftheiroffspring.Usethe slopeofthis
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relationshiptoestimateheritability.Thisstepwillenableustoanswer
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question,“Whatistheheritabilityofmetaltoleranceinthepopulationofsunstalks?”
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Step1:Interpretingheritability. c c c




Because the genotype of an offspring depends on the alleles inherited from its parents, we can
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predict the genotype of an offspring from the genotypes of its parents. Then, we can use an
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expected genotype toinferthe phenotype.
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Despiteourabilitytoinferphenotypefromgenotype,thegenotypeofanorganismonly partially
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determinesitsphenotype.Environmentalfactorsalsoaffectthephenotype.For example,
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temperature and nutrients affect how an organism grows and develops, leading to variationinatrait
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withinapopulationoforganisms.Thisvariationresultingfromthe environmentisnotinherited
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withtheallelesfromparents.Onlythegeneticportionof phenotypicvariationpassesfromparent
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tooffspringthroughalleles.
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, Whatis heritability?
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Heritability is defined as the proportion of phenotypic variation in a population that stems from
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additive effects of alleles. In other words, heritability is the proportion of phenotypic variation
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causedbygenes,ratherthantheenvironment.
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Heritability reflects the extent to which the phenotypes of parents determine the phenotypes of
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their offspring. Thus, heritability reflects a relationship between the phenotypes of parents andthe
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phenotypesofoffspring.Wecanusealinearfunctiontodescribethisrelationship,in whichthe
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independentvariableisthemeanphenotypeofparentsandthedependent variableisthemean
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(orexpected)phenotypeofanoffspring.Let’sconsideranexample.
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Imagine two traits, which we will call trait 1 and trait 2. Figure 1 shows the linear
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relationship between the mean parental phenotype and the mean offspring
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phenotypeforeachtrait.
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