Lab 6

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1. Why are spindle fibers important for mitosis? (5 points) Chromosomes use spindle fibers as pathways to daughter cells during mitosis.
2. State the four bases that make up DNA. (4 points)
a. Adenine
b. Guanine
c. Thymine
d. Cytosine
3. What are the two base pairs? (2 points)
a. T & C
b. A & G
4. Answer the following questions:
a. Define the term crossing over. (3 points) During meiosis’ prophase the homologous chromatids exchange segments.
b. Explain why crossing over is important in meiosis. (3 points) Parents cell use it to pass genes off to their children cells.
5. What are the two main differences between mitosis and meiosis? (4 points)
a. The amount of cell divisions
b. The genes that are exchanged between chromosomes
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(5 points)
a. Interphase B
b. Prophase C
c. Metaphase E
d. Anaphase A
e. Telophase/cytokinesis D
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) 38P/33Y = 1.15:1
b. What was the phenotypic frequency from Step 2? (2 points) 49P/11Y = 4.45:1
c. What was the phenotypic frequency from Step 3? (2 points) 5PW/16PS =0.28:1 2YW/4YS=0.5:1
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)
D, Y

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) 3:1
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) There was difference or one
14. Recall from the background

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