Week 13 laboratory reflection - Mendelian Genetics and Drosophila II

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Indiana University, Bloomington *

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Biology

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Dec 6, 2023

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Name: Laboratory Reflection: Mendelian Genetics and Drosophila (Part II) Instructions: Make sure to scroll through the entire document to answer all questions. It would also help with grading if you put your typed answers in a different (but readable) color font . Save and upload your completed assignment to the associated assignment page on Canvas. It is the student’s responsibility to confirm that the correct file was submitted to Canvas by the due date. In week 13, you were given F2 progeny from a previously set-up genetic cross. You were tasked with determining if the mutant phenotype observed within your cross was due to a dominant or recessive allele, as well as, it’s inheritance pattern (i.e. autosomal vs sex-linked). To accomplish this task, you (1) determined the expected outcomes for different cross types, (2) collected observed data by scoring F2 phenotypes, and (3) compared the expected and observed values using a Chi-square test. In the following assignment, you will repeat this task using data from a hypothetical example. Scenario: You are a student researcher working in a genetics lab at IU. Your professor has discovered a new mutant phenotype in Drosophila resulting in pink body color. They have tasked you with determining if the allele responsible for pink body color is recessive or dominant and if the allele is found on an autosome or on a sex chromosome. Specifically, they want you to test the following three predictions: 1) The mutant allele is recessive and is located on an autosome 2) The mutant allele is dominant and is located on an autosome 3) The mutant allele is recessive and is located on the X chromosome To help you accomplish this task, your professor gives you a vial of F2 offspring resulting from a two-generation cross between true-breeding wildtype females and true-breeding pink-bodied males. You score F2 phenotypes for a total of 120 flies and obtain the following data: 1. Base d on the above observed data, determine the expected number of flies for the following three scenarios provided in a-c below. Refer to your laboratory protocols if you need a refresher on how to calculate expected numbers. Show your work within each cell of the table. a. (1pt) The mutant allele is recessive and is located on an autosome: 1 Wildtype body color Pink body color Males Female Males Females Number of flies observed 20 14 39 47

Wildtype body color Pink body color Males Female Males Females Expected number of flies b. (1pt) The mutant allele is dominant and is located on an autosome c. (1pt) The mutant allele is recessive and is located on the X chromosome 2. Exam ining your observed and expected values: a. (1pt) Is the mutant allele recessive or dominant? Explain your logic. b. (1pt) Is the mutant allele on an autosome or on the X chromosome? Explain your logic c. (1pt) Which of the three predictions is most likely, given the observed data? 1) The mutant allele is recessive and is located on an autosome 2) The mutant allele is dominant and is located on an autosome 3) The mutant allele is recessive and is located on the X chromosome 3. Statistically verify the prediction that you selected as the most likely using a Chi-square test ( https://www.graphpad.com/quickcalcs/chisquared1/ ). Refer to your laboratory protocols if you need a refresher on how to complete the Chi-square test. 2 Wildtype body color Pink body color Males Female Males Females Expected number of flies Wildtype body color Pink body color Males Female Males Females Expected number of flies

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