Pearland Independent School District



Name: Date: _ Period: Virtual Lab: Sex-Linked TraitsVirtual Lab: Sex-Linked TraitsGenetics Purpose: Explore sex-linked gene for eye color in Drosophila flies.Objective: Construct and Analyze Punnett square for monohybrid genetic crosses involving sex-linked traits.When completing post lab questions please refer to your textbook device for explanationGo to: on the T.V. screen found in your virtual lab. Watch the short video.1. Please make sure you have read through all of the information in the “Questions” and “Information” areas. If you come upon terms that are unfamiliar to you, please refer to your textbook for further explanation.2. Next, complete the Punnett square activity by clicking on the laboratory notebook. Please be sure to note the possible genotypes of the various flies:Female, red eyesFemale, red eyesFemale, white eyesMale, red eyesMale, white eyesWhen you have completed the Punnett square activity, return to the laboratory scene to begin the actual laboratory activity.3. In this exercise, you will perform a Drosophila mating in order to observe sex-linked trait transmission. Please click on the shelf in the laboratory. Here you will find vials of fruit flies. On the TOP shelf, please click on one of the female vials (on the left side) and then drag it to the empty vial on the shelf below. Please repeat this step using one of the male vials (on the rightside). These flies will be used as the parental (P) generation. You may switch your parent choices at any time by dragging out old selections and dragging in new flies. Use the Punnett squarebelow to PREDICT the genotypes/phenotypes of the offspring (Note: refer to the genotype table you created above if needed):18732546355Predict % of each0Predict % of each % Female, red eye _% Female, white eye % Male, red eye % Male, white eyeWhen you are finished, click “Mate and Sort”.4. You will now see information appear in the vials sitting on the next shelf below. These are the offspring of the parent flies you selected above, and they represent the first filial (F1) generation. In Table I, input the numbers of each sex and phenotype combination for the F1 generation. These numbers will be placed into the first row marked “P generation Cross”.5. You will next need to select one of the F1 female flies and one of the F1 male flies to create the second filial (F2) generation. Drag your selections down to the empty vial on the next shelf below and fill in the Punnett square below to PREDICT the offspring:left140335Predict % of each0Predict % of each % Female, red eye _% Female, white eye % Male, red eye % Male, white eyeAfter clicking “Mate and Sort”, you will now have information on their offspring (the F2 generation) to input into your Table I. This information will be placed into the second row marked “F1 generation Cross”.NOTE: Rest the program and complete another trial using different fly typesTable I:-2667002312670Trial 2Trial 2-2381251131570Trial 1Trial 1CrossTypePhenotypeof MaleParentPhenotypeof FemaleParentNumberof Red eye, Male OffspringNumberof White eye, Male OffspringNumberof Red eye, Female OffspringNumberof White eye, Female OffspringPGenerationCrossF1GenerationCrossPGenerationCrossF1GenerationCrossPost-Lab Questions 1.Through fruit fly studies, geneticists have discovered a segment of DNA called the homeobox which appears to control:a. Sex development in the flies b. Life span in the fliesc. Final body plan development in the flies2.The genotype of a red-eyed male fruit fly would be:a. XRXR b. XRXr c. XrXrd. A or Be. None of the above3.Sex-linked traits:a. Can be carried on the Y chromosome b. Affect males and females equallyc. Can be carried on chromosome 20 d. A and Be. None of the above4.A monohybrid cross analyzes:a. One trait, such as eye colorb. Two traits, such as eye color and wing shape c. The offspring of one parent5. A female with the genotype “XRXr”:a. Is homozygous for the eye color gene b. Is heterozygous for the eye color genec. Is considered a carrier for the eye color gene d. A and Be. B and C6. In T.H. Morgan’s experiments:a. He concluded that the gene for fruit fly eye color is carried on the X chromosomeb. He found that his F1 generation results always mirrored those predicted by Mendelian Laws ofInheritancec. He found that his F2 generation results always mirrored those predicted by Mendelian Laws ofInheritance d. A and Be. All of the above7.In this laboratory exercise:a. The Punnett square will allow you to predict the traits of the offspring created in your crosses b. XR will represent the recessive allele for eye color, which is whitec. Xr will represent the dominant allele for eye color, which is red d. All of the above8.In a cross between a homozygous red-eyed female fruit fly and a white-eyed male, what percentage of the female offspring is expected to be carriers?a. 0%b. 25%c. 50%d. 100%9.In a cross between a white-eyed female and a red-eyed male:a. All males will have red eyesb. 50% of males will have white eyes c. All females will have red eyesd. 50% of females will have white eyes10. In human diseases that are X-linked dominant, one dominant allele causes the disease. If an affected father has a child with an unaffected mother:a. All males are unaffectedb. Some but not all males are affected c. All females are unaffectedd. Some but not all females are affectedQuestions: Put any Punnett squares on a piece of notebook paper, Staple it to the back of lab1097280716280001. In a mating between a red-eyed male fruit fly and a red-eyed heterozygous female, what percentage of the female offspring is expected to be carriers? How did you determine the percentage?1097280-160020001097280716280002. In a mating between a red-eyed male fruit fly and a white-eyed female fruit fly, what percentage of the male offspring will have white eyes? Describe how you determined the percentage.1097280-16002000109728010674350010972801417955003. Hemophilia, a blood disorder in humans, results from a sex-linked recessive allele. Suppose that a daughter of a mother without the allele and a father with the allele marries a man with hemophilia. What is the probability that the daughter's children will develop the disease? Describe how you determined the probability.1097280-335280004. Colorblindness results from a sex-linked recessive allele. Determine the genotypes of the offspring that result from a cross between a color-blind male and a homozygous female who has normal vision. Describe how you determined the genotypes of the offspring.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________914400541020005. Explain why sex-linked traits appear more often in males than in females.914400-51054000914400-160020009144001242060006. In humans, hemophilia is a sex-linked recessive trait. It is located on the X chromosome. Remember that the human female genotype is XX and the male genotype is XY. Suppose that a daughter of a mother without the allele and a father with the allele marries a man with hemophilia. What is the probability that the daughter's children will develop the disease? Describe how you determined the probability.914400-51054000914400-160020007. Colorblindness also results from a sex-linked recessive allele on the X chromosome in humans.91440087312500Determine the genotypes of the offspring that result from a cross between a color-blind male and a homozygous female who has normal vision. Describe how you determined the genotypes of the offspring.914400-51054000914400-16002000914400716915009144001067435009144001417955008. Based on the traits explained in questions 6 and 7, explain why sex-linked traits in humans appear more often in males than in females. ................
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