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: B B




The breeding experiment of sunstalks was a success! From this experiment, we learned that
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metal tolerance is indeed a heritable trait. However, as is the case with many traits, metal
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tolerance in sunstalks is a continuous variable that depends on hundreds of genes.
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BTherefore, it would be impractical to use gene-editing tools to save the population sunstalks.
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Instead, we selected sunstalks with sufficient metal tolerance and transplanted them to the
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contaminated areas of the sanctuary, hopefully giving the stalkleapers a chance for survival as
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well.
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Unfortunately, our solution to one problem inadvertently caused another problem: one of
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the genes for metal tolerance is linked to a gene trait that enables the azure pods’ to close in
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response to a chemical stimulus from the stalkleapers. These pods must close properly to
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protect the stalkleapers from their predators. Given that a single gene affects this function of
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the azure pods, we can edit this gene to correct the problem in real time, preventing the
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collapse of an entire ecosystem.
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To save the sunstalks and the stalkleapers, we must apply our understanding of genetics and
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evolution to this problem. Use the following questions to guide your work:
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● What is the heritability of metal tolerance in the population of sunstalks?
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● Will the mean metal tolerance evolve rapidly enough for the population of
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stalkleapers to persist?
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● How should we edit the DNA of a sunstalk to restore its ability to close its azure
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pods? B




Universally in your debt, B B B




The AI B




Page 1 B

, Appendix 1 B




What is the heritability of metal tolerance in the population of sunstalks?
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Before we resort to gene editing, we must be sure that natural selection will enable the
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sunstalks to adapt to the contaminated soil in the sanctuary. The rate at which a trait evolves
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by natural selection depends on several factors, including the amount of heritable
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variation in the trait. By estimating the heritability of metal tolerance, we can get a step closer
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to determining how quickly the sunstalks can adapt to their environment.
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We will follow two key steps to answer the question, “What is the heritability of metal
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tolerance in the population of sunstalks?”
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Step 1: Interpreting heritability. Compare and interpret estimates of heritability between
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traits. This step will prepare you to estimate the heritability of metal tolerance in Step 2.
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Step 2: Estimate the heritability of metal tolerance. Plot the linear relationship between the
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mean metal tolerance of parents and the mean metal tolerance of their offspring. Use the
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slope of this relationship to estimate heritability. This step will enable us to answer the
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question, “What is the heritability of metal tolerance in the population of sunstalks?”
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Step 1: Interpreting heritability. B B B




Because the genotype of an offspring depends on the alleles inherited from its parents, we
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can predict the genotype of an offspring from the genotypes of its parents. Then, we can use
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an expected genotype to infer the phenotype.
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Despite our ability to infer phenotype from genotype, the genotype of an organism only
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partially determines its phenotype. Environmental factors also affect the phenotype. For
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example, temperature and nutrients affect how an organism grows and develops, leading to
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variation in a trait within a population of organisms. This variation resulting from the
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environment is not inherited with the alleles from parents. Only the genetic portion of
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phenotypic variation passes from parent to offspring through alleles.
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, What is heritability?
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Heritability is defined as the proportion of phenotypic variation in a population that stems
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from additive effects of alleles. In other words, heritability is the proportion of phenotypic
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variation caused by genes, rather than the environment.
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Heritability reflects the extent to which the phenotypes of parents determine the phenotypes
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of their offspring. Thus, heritability reflects a relationship between the phenotypes of parents
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and the phenotypes of offspring. We can use a linear function to describe this relationship, in
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which the independent variable is the mean phenotype of parents and the dependent
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variable is the mean (or expected) phenotype of an offspring. Let’s consider an example.
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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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Bphenotype for each trait. B B B




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