bio lab 156 lab 6

Topics: Chromosome, Mitosis, Cell Pages: 5 (927 words) Published: July 31, 2015
1. Why are spindle fibers important for mitosis? (5 points) Spindle fibers work as a path for chromosomes to travel(Campbell, 2009). 2. State the four bases that make up DNA. (4 points)
a. (A)-Adenine
b. (G)-Guanine
c. (T)-Thymine
d. (C)-Cytosine (Campbell, 2009).
3. What are the two base pairs? (2 points)
a. AG
b. CT
4. Answer the following questions:
a. Define the term crossing over. (3 points)
The phase in meiosis where chromosomes exchange segments of genetic materials (Campbell, 2009). b. Explain why crossing over is important in meiosis. (3 points) Crossing over is the way that genes receive genetic traits from both of the parents. 5. What are the two main differences between mitosis and meiosis? (4 points) a. Crossing over does not occur in mitosis

b. The number of cells exchanged is different and mitosis occurs in all organisms and meiosis only occurs in certain organisms and the number of cells (Campbell, 2009). 6. Answer the following questions:

a. Explain the difference between mitosis and cytokinesis. (3 points) Firstly mitosis occurs before cytokinesis. Mitosis results in growth of cells and cytokinesis is for maintenance. Mitosis divides a cell’s nucleus and cytokinesis divides the cytoplasm (Campbell, 2009). b. When does mitosis occur during the cell cycle? (1 point)

Throughout the whole cell cycle
c. When does cytokinesis occur during the cell cycle? (1 point) Telophase
7. Explain the differences that occur during cytokinesis of plant and animal cells. (5 points) In animal cells the cell is pinched creating a cleavage furrow that allows it to be split the cytoplasm. In plant cells the wall is too rigid so the plasma membrane and cell wall have to grow inward together in order to be split (Campbell, 2009). 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)  

9. Refer to the image below. What stage of mitosis is the cell below undergoing? (1 point)  Metaphase

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)  

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) 1:1 b. What was the phenotypic frequency from Step 2? (2 points) 3:1 c. What was the phenotypic frequency from Step 3? (2 points) 9:3:3:1 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) A.PP

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) It was an equal 1:1 ratio.

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)

It ended up being a much smaller ratio (from 3:1 to 1:1)
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,...
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