Biology

To set up a cross between two F1 offspring to produce an F2 generation, be sure that you are looking at the two wild-type offspring flies in the box at the bottom of the screen. If not, scroll to the bottom of this box until the word “Offspring” appears in the center of the box. Click the Select button below the female wild-type fly image, then click the Select button below the male wild-type fly image. Note that the two F1 offspring that you just selected appear at the top of the screen as the flies chosen for your new mating. Click on the Mate button between the two flies. The F2 generation of flies now appears in the box at the bottom of the screen. Use the scroll buttons to view the phenotypes of the F2 offspring.

Examine the results of this cross and save the results to your lab notes. . Tabulate your data and present it. Provide a punnet square, tabulate data.. What is the phenotypic ratio of the F2 offspring? What are the phenotypes of the F2 offspring? (2pts)

Respond to question 3 here 

4. To validate or reject a hypothesis, perform a Chi-square analysis as follows. Click on the Chi-Square Test button on the lower left side of the screen. To ignore the effects of sex on this cross, click on the Ignore Sex button. Enter a predicted ratio for a hypothesis that you want to test. For example, if you want to test a 4:1 ratio, enter a 4 in the first box under the Hypothesis column and enter a 1 in the second box. To evaluate the effects of sex on this cross, simply type a 4 in each of the first two boxes, and type a 1 in each of the last two boxes. Click the Test Hypothesis button at the bottom of the panel. A new panel will appear with the results of the chi-square analysis. Note the level of significance displayed with a recommendation to either reject or not reject your hypothesis.

What was the recommendation from the chi-square test with a 4:1 ratio? Was your ratio accepted or rejected. . Tabulate your data and present it. (2pts)

Respond to question 4 here 

5. Repeat the Chi-square analysis with a new ratio until you discover a ratio that will not be rejected.

5a. What did you discover to be the correct phenotypic ratio for this experiment? . Tabulate your data and present it. Was this what you expected? Why or why not? (2pts)

5b.What do the results of this experiment tell you about the dominance or recessiveness of the sepia allele for eye color? (2pts)

Respond to question 5a here 

Respond to question 5b here 

6. Click on the New Mate button in the lower left corner of the screen to clear your previous cross.

6a. Examine the results of this cross and save the results to your lab notes. . Tabulate your data and present it. Provide a punnet square, tabulate data. Following the procedure described above, perform monohybrid crosses for at least three other characters. For each cross, develop a hypothesis to predict the results of the phenotypes in the F1 and F2 generations and perform chi-square analysis to compare your observed ratios with your predicted ratios. Tabulate your data and present it. (6pts)

6b. Examine the results of this cross and save the results to your lab notes. Tabulate your data and present it. For each individual cross, try varying the number of offspring produced. What effect, if any, does this have on the results produced and your ability to perform chi-square analysis on these data? Tabulate your data and present it. (Hint: what happens to the size of the sums of squres and the estimate of Chi-square as the number of progeny are increased?)(6pts)

6c. If any of your crosses do not follow an expected pattern of inheritance, provide possible reasons to account for your results. Some of the characteristics available in this simulation are inherited via simple mendelian genetics (one copy of the dominant allele masks the expression of the recessive allele and some are sex-linked. The expected phenotypic ratios will be different (CC p176) (3pts)

Respond to question 6a character #1 here 

Respond to question 6a character #2 here 

Respond to question 6a character #3 here 

Respond to question 6b here 

Respond to question 6c here 

7. Once you are comfortable with using FlyLab to perform a monohybrid cross, design a dihybrid cross by selecting and crossing an ebony body female fly with a male fly that has the vestigial mutation for wing size.

7a. Develop a hypothesis to predict the phenotypic ratio in the F1 and F2 progeny of this cross and describe each phenotype that you would expect to see in both the F1 and F2 generations of this cross. For example a phenotypic ratio could be 3:1 or 1:1:1:1 or 9:3, it isn’t just words. (2pt)

7b. Examine the results of this cross and save the results to your lab notes. . Tabulate your data and present it. Provide a punnet square, tabulate data.. Describe the phenotypes that you observed in both the F1 and F2 generations of this cross. How does the observed phenotypic ratio for the F2 generation compare with your predicted phenotypic ratio? Explain your answer. (5pts)

Respond to question 7a here 

Respond to question 7b here 

8. Use FlyLab to perform a trihybrid cross by designing and crossing a wild-type female fly and a male fly with dumpy wing shape, ebony body color, and shaven bristles.

8a. Develop a hypothesis to predict the phenotypic ratio in the F1 and F2 progeny of this cross and describe each phenotype that you would expect to see in both the F1 and F2 generations of this cross. (2pt)

8b. Examine the results of this cross and save the results to your lab notes. Tabulate your data and present it. Perform your cross and evaluate your hypothesis by Chi-square analysis. What was the trihybrid phenotypic ratio produced for the F2 generation? . Tabulate your data and present it. Provide a punnet square, tabulate data. (5pts)

Respond to question 8a here 

Respond to question 8b here 
Assignment #2

A testcross is a valuable way to use a genetic cross to determine the genotype of an organism that shows a dominant phenotype but unknown genotype. For instance, using Mendel’s peas, a pea plant with purple flowers as the dominant phenotype could have either a homozygous or a heterozygous genotype. With a testcross, the organism with an unknown genotype for a dominant phenotype is crossed with an organism that is homozygous recessive for the same trait. In the animal- and plant-breeding industries, testcrosses are one way in which the unknown genotype of an organism with a dominant trait can be determined. Perform the following experiment to help you understand how a testcross can be used to determine the genotype of an organism.

9. Design a female fly with brown eye (BW) color (keep all other traits as wild-type), and design a male fly with ebony body color (E; keep all other traits as wild-type). Mate the two flies. Examine the F1 offspring from this cross and save your data to your lab notes. Add to your data any comments that you would like. To determine the genotype of an F1 wild-type female fly, design a male fly with brown eye color and ebony body color, then cross this fly with an F1 wild-type female fly.

Examine the results of this cross and save the results to your lab notes. Tabulate your data and present it. What was the phenotypic ratio for the offspring resulting from this testcross? Show work! Tabulate your data and present it. (5pts)

Respond to question 9 here 

10a. Based on the phenotypic ratio, determine whether the F1 wild-type female was double homozygous or double heterozygous for the eye color and body color alleles. Show work ! (5pts)

10b. Explain your answer. If your answer was double homozygous, describe an expected phenotypic ratio for the offspring produced from a testcross with a double heterozygous fly. If your answer was double heterozygous, describe an expected phenotypic ratio for the offspring produced from a testcross with a homozygous fly. Show work! This requires a punnet square (5pts)

Respond to question 10a here 

Respond to question 10b here 

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