Linkage and Mapping Homework Biology 210 1. Two loci found in mice are suspected to be linked. To test this alternative hypothesis, a group of graduate students performed a test cross between mice that are true breeding for both dominant phenotypes and mice that are true breeding for both recessive phenotypes. Individuals from the \( \mathrm{F}_{1} \) generation were crossed with individuals that express both recessive phenotypes. The phenotypic results are shown in the table below. Use chi-square analysis to determine if the graduate students' hypothesis is supported by the evidence. \begin{tabular}{lc} Phenotype & Number of Offspring \\ Dominant 1, Dominant 2 & 182 \\ Recessive 1, Recessive 2 & 168 \\ Dominant 1, Recessive 2 & 156 \\ Recessive 1, Dominant 2 & 144 \end{tabular} a. (1 pt) What are the degrees of freedom and the critical chisquare value? b. (1 pt) What is the calculated chi-square value? c. (1 pt) Do the results support that the loci are linked or that they are independently assorted (unlinked)? 2. Two linked loci have a recombination frequency of \( 19 \% \). A series of crosses is performed. The P generation includes an individual that is homozygous dominant for trait 1 and homozygous recessive for trait 2. The second individual in the cross is homozygous recessive for trait 1 and homozygous dominant for trait 2. The \( \mathrm{F}_{1} \) generation is crossed with
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Step 1: **Determine the Expected Ratios** For a test cross involving two loci, if the loci are independently assorted (unlinked), the expected phenotypic ratio is 1:1:1:1. Show moreā¦
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c) First, test the data against the hypothesis of independent assortment using a chi2 test and expected values based on the assumption of independent assortment in the cross. State your p value, conclusion, and an alternate hypothesis. Gen. | Obs | Exp. | (O-E)^2/E --- | --- | --- | --- B-P- | 103 | 75 | 10.45 B-pp | 49 | 75 | 9.01 bbP- | 44 | 75 | 12.81 bbpp | 104 | 75 | 11.21 3 P VALUE > 0.01 NULL = REJECTED 43.46 = x^2 ALTERNATE HYPOTHESIS IS THAT THE GENES DO NOT SHOW THE GIVEN A. d) Now test the data against a more reasonable hypothesis, say for instance that the genes are linked and separated by a recombination distance of 25.0 cM; Use the 25.0 cM value to generate expected values for an experimental population of 300 individuals. State your p value and conclusion. GAMETES = 100% RECOMB. GAMETES = 25% PARENTAL GAMETES = 75% | | bp | 100% --- | --- | --- 37.5 BP | BPbp | 37.5% 12.5 Bp | Bpbp | 12.5% 12.5 bP | bPbp | 12.5% 37.5 bp | bbpp | 37.5% e) Now, calculate the linkage of the genes and show a genetic map from the observed data above.
Madhur L.
Variation in the length of their tail. Adults of this species can have a tail of any length between 1-10 inches. In this imaginary species, tail length is affected by four genes: E, F, G, and H. Genes E, F, and G are all located on the same autosomal chromosome, while gene H is X-linked. The number of dominant alleles present in these genes determines the tail length. There is a general correlation between the total number of dominant alleles an individual has across all four of these genes and the length of the mouse tail. Consider the following two mice: a male with a 5.6 inch tail with genotype EeFfGgXHY, and a female with a 2.2-inch tail with genotype eeffGGXhXh. a) In this example, are all 4 of these genes considered linked with each other? If so, explain why. If not, state which genes are considered linked with each other and explain why. b) For a mating between mouse 1 and mouse 2, is it possible for them to have a male offspring that has at least one dominant allele at each of the 4 loci? Explain why or why not (be specific about how the relevant alleles would be inherited). c) For a mating between mouse 1 and mouse 2, is it possible for them to have male offspring that have tails substantially longer than that of mouse 1? Explain why or why not (be specific about how the relevant alleles would be inherited from each parent). d) You measure the tails of other mice with the same genotype as mouse 1 and find that even though they have the same genotype they each have slightly different tail lengths ranging from 5.3-5.9 inches. What is the most likely explanation for this finding? Propose a specific, testable hypothesis to explain
Katlin K.
Studies like the one described in question AP12.1 were carried out by Morgan and Sturtevant beginning in 1911. The discovery of linkage was made by Bateson and Punnett in 1900. They crossed a true-breeding purple (P) plant with long seeds (L) with a true-breeding red (r) plant with round seeds (l). They then performed a self-cross between the $\mathrm{F}_{1}$ generations. They obtained the $\mathrm{F}_{2}$ data shown below. A. Use the symbols $\mathrm{P}, \mathrm{p}, \mathrm{L},$ and 1 to construct a representation of the $\mathrm{F}_{2}$ genotypes and complete the second column in the table. B. Complete the fourth column of the table above by recording the values of the predicted numbers of plants with each genotype. C. Apply a c' test at the 95$\%$ confidence level to evaluate the claim that these data confirm linkage. The definition of the statistic $\chi^{2}=\sum \frac{(o-e)^{2}}{e}$ and this table are provided in the AP Biology Exam. D. At first, Bateson and Punnett did not see that these genes are located on the same chromosome and proceeded to measure the linkage distance between them, taking the first step toward creating a gene map. Justify the selection of data and the procedure from which data could be collected that would have provided the necessary evidence to confirm linkage and recombination.
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