PART III: Calculating the frequency of corn kernel characteristics
In this part of the lab, frequencies of two corn kernel characteristics will be determined: kernel color and kernel texture. In observing the ears of corn, note that the kernels are either purple or yellow and that they are either smooth or wrinkled. With respect to color, purple is the dominant color, and yellow is the recessive color. With respect to texture, smooth is the dominant texture, and wrinkled is the recessive texture. Use the following designations for each trait: purple (P); yellow (p); smooth (S); wrinkled (s). Keep this information available as it will be needed later on in the lab.
1. Observe the image of a corn ear below. Notice that the ear of corn contains purple and yellow kernels. Study the image and then count three rows of kernels, tallying the number of purple and the number of yellow kernels. Record this information on a piece of paper to refer to later in this laboratory. Review the results and indicate the frequency (ratio) of purple to yellow kernels.
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Click on image to enlarge.
2. Observe this second image of a corn ear below. Notice that the ear of corn contains purple and yellow kernels. Study the image and then count three rows of kernels, tallying the number of purple and the number of yellow kernels. Record this information on a piece of paper. Review the results and indicate the frequency (ratio) of purple to yellow kernels.
Click on image to enlarge.
3. Observe this third image of a corn ear below. Notice that the ear of corn contains purple and yellow kernels. Additionally, notice that some of the corn kernels are smooth and some of the corn kernels are wrinkled. Study the image and then count three rows of kernels, tallying the number of kernels. For this exercise, there are four different kernels to count: purple and smooth, purple and wrinkled, yellow and smooth, or yellow and wrinkled. Record this information on a piece of paper. Review the results and indicate the frequency (ratio) of corn kernels.
Click on image to enlarge.
Assessing Your Learning
Compose answers to the questions below in Microsoft Word and save the file as a backup copy in the event that a technical problem is encountered while attempting to submit the assignment. Make sure to run a spell check. Copy the answer for the first question from Microsoft Word by simultaneously holding down the Ctrl and A keys to select the text, and then simultaneously holding down the Ctrl and C keys to copy it. Then, click the link on the Lab Preview Page to open up the online submit form for the laboratory. Paste the answer for the first question into the online dialog box by inserting the cursor in the box and simultaneously holding down the Ctrl and V keys. The answer should now appear in the box. Repeat this process for each question. Review all work to make sure that all questions have been completely answered and then click on the Submit button at the bottom of the page.
LAB 6
1. Why are spindle fibers important for mitosis? (5 points)
2. State the four bases that make up DNA. (4 points)
a.
b.
c.
d.
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3. What are the two base pairs? (2 points)
a.
b.
4. Answer the following questions:
a. Define the term crossing over. (3 points)
b. Explain why crossing over is important in meiosis. (3 points)
5. What are the two main differences between mitosis and meiosis? (4 points)
a.
b.
6. Answer the following questions:
a. Explain the difference between mitosis and cytokinesis. (3 points)
b. When does mitosis occur during the cell cycle? (1 point)
c. When does cytokinesis occur during the cell cycle? (1 point)
7. Explain the differences that occur during cytokinesis of plant and animal cells. (5 points)
8. Refer to the images below, labeled A through E. Each image details a stage of the cell cycle for a cell undergoing mitosis. Place the images in correct order by placing the letters in the correct sequence, according to the stages of mitosis. (5 points)
a. Interphase
b. Prophase
c. Metaphase
d. Anaphase
e. Telophase/cytokinesis
9. Refer to the image below. What stage of mitosis is the cell below undergoing? (1 point)
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10. Refer to the images below. Place the cells identified with the letters A through E in correct order for a cell undergoing mitosis. (5 points)
a. Interphase
b. Prophase
c. Metaphase
d. Anaphase
e. Telophase/cytokinesis
11. Refer to the data on the corn kernel color frequency from Part III of the lab. (Remember there were four possible types for this part of the lab.)
a. What was the phenotypic frequency from Step 1? (2 points)
b. What was the phenotypic frequency from Step 2? (2 points)
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c. What was the phenotypic frequency from Step 3? (2 points)
12. Recall from the background information that purple corn kernels are dominant and yellow kernels are recessive. The second ear of corn was the result of crossing two heterozygous ears of male purple corn (Pp x Pp). This is represented by the Punnett square below. Complete the Punnett square by writing the correct letters that correspond to each number indicated in the table. (4 points)
P p
P 1 2
p 3 4
13. Once the Punnett square for Question 12 is complete, calculate the ratio of purple and yellow kernels (recall that if the dominant trait is present, it will be expressed).
a. What is the ratio of purple to yellow kernels based on the Punnett square? (5 points)
b. How did this compare to the ratio obtained from counting the corn kernels for ear number two in part III of the lab? (5 points)
14. Recall from the background information that purple kernels are dominant and yellow kernels are recessive. Also recall that smooth kernels are dominant and wrinkled kernels are recessive. The third corn ear was the result of crossing a male ear of corn with the following gametes, PpSs, with a female ear of corn with the same gametes, PpSs. This is represented by the Punnett square below. Complete the Punnett square by writing the correct letters that correspond to each number indicated in the table (for example, PPSS or ppss). (8 points)
PS Ps pS ps
PS 1 2 3 4
Ps 5 6 7 8
pS 9 10 11 12
ps 13 14 15 16
15. Once the Punnett square for Question 14 is complete, calculate the ratio of corn kernel varieties (recall that if the dominant trait is present, it will be expressed).
a. What is the ratio of all kernel varieties based on the Punnett square? (5 points)
b. How does this compare to the ratio obtained from counting the corn kernels? (5 points)
16. (Application) How might the information gained from this lab pertaining to mitosis and meiosis be useful to a student employed in a healthcare related profession? (20 points)
Have You Met The Objectives For This Lesson?
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