D16 act-Sex Determination copy

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Central Michigan University *

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Biology

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Apr 25, 2024

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BIO 211 Activities: Day 16 Sex Determination and Dosage Compensation For each activity, decide who will verbally explain if your group is called on! 1. Sex Determination: Necessary vs. Sufficient (APPLY) Necessary vs. sufficient: taco example If I remove the spicy taco sauce, it is no longer flavorful. Therefore, spicy taco sauce is necessary for flavor. However, we don’t know from this “experiment” if the sauce is sufficient for flavor. If I give you a plan taco with meat and cheese, it is not flavorful. If I then add spicy taco sauce, it becomes flavorful. That “experiment” tells us the sauce is sufficient for flavor Add = sufficient Remove = necessary a. Necessary vs. sufficient in an experiment: If you have an experiment that adds in a factor/gene, then you conclude if the gene is ___ Sufficient __ (pick necessary or sufficient). If you have an experiment that removes a factor/gene, then you can conclude if the gene is ___ Necessary ___ (pick necessary or sufficient). b. Interpreting results of SRY experiment In this experiment, genotypically female mice were given an extra copy of the SRY gene. The mice with SRY added became phenotypically male. From this experiment, is SRY _necessary__ for maleness? (Choose from: Yes/No/Did not test) – Did not test From this experiment, is SRY is _sufficient __ for maleness? (Choose from: Yes/No/Did not test – Yes c. Sex determination in Drosophila. Does the Y chromosome determine male-ness in flies as it does in humans? No Design an experiment to determine whether the Y chromosome determines sex in fruit flies. Remove a Y chromosome from a XY fly to see if its necessary Add a Y chromosome to a XX fly to see if its sufficient 2. Sex determination in Drosophila and dosage compensation Ratio Sex(X):autosomal a. Use the rules in the table to determine the sex of these flies: The sex of an XO fruitfly with a normal number of autosomes (two sets) is _ male _ because the ratio of X chromsomes to autosomes is _ 0.5 __. A fruitfly is found that has three sex chromosomes (XXY) and three sets of autosomes. The sex of this fruitfly is intersex because the ratio is _ 0.667 __. A different fruitfly has three sex chromosomes (XXX) and two sets of autosomes. The sex of this fruitfly is ___ metafemale ___ because the ratio is __ 1.5 __. b. Dosage compensation in mammals How many Barr bodies do you expect in: i. An _XX_ individual _ 1_ __ ii. An _XXY_ individual __ 1 __
iii. An _XXXX_ individual _3__ iv. An _XO_ individual _ 0 _ c. Sex testing and athletics. Maria was born in 1961 and was a world class hurdler from Spain. Starting in 1968 the Olympics required female sex testing. She passed a sex test in 1983 (“certificate of femininity”). In 1985, she took another sex test which found that she was XY. One of the tests Maria took was a Barr body test. How many Barr bodies did Maria have? She would have zero bar bodies What are some reasons why Maria might have been assigned female at birth (and later gynecological exams agreed), but XY, with no medical intervention? The SRY gene on the Y chromosome could be inactive or missing. For more information (optional): https://www.nature.com/articles/gim2000258.pdf?origin=ppub https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3007680/ https://link.springer.com/article/10.1007/s10508-021-02073-x
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