Lab 3 mitosis and meiosis answers

Access Code (located on the lid of your lab kit):

Pre-Lab Questions

”1. What are chromosomes made of?”

”2. Compare and contrast mitosis and meiosis. ”

”3. Cancer is a disease related to uncontrolled cell division. Investigate two known causes for these rapidly dividing cells and use this knowledge to invent a drug that would inhibit the growth of cancer cells. ”

Experiment 1: Observation of Mitosis in a Plant Cell

Table 1: Mitosis Predictions

Predictions

Duplication of original cell and its contents

Supporting Evidence

A single cell undergoes division to form two cells each with its own cell contents

Table 2: Mitosis Data

Chosen Image

Observation

Stage

Number of Cells in Stage

Total Number of Cells

Calculated % of Time Spent in Stage

Interphase

5

13

2

Prophase

2

10

3

Metaphase

3

9

1

Anaphase

7

12

4

Telophase

2

17

2

Cytokinesis

1

6

5

Table 3: Stage Drawings

Cell Stage

Drawing REMEMBER: Your drawings should have your name and access code handwritten in the background.

Interphase

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

Post-Lab Questions

”1. Label the arrows in the slide image below with the appropriate stage of the cell cycle. ”

A- prophase

B- anaphase

C- metaphase

D- interphase

E- telophase

F- anaphase

”2. What stage were most of the onion root tip cells in? Why does this make sense? ”

Telophase. Most onion cells are rapidly dividing

”3. As a cell grows, what happens to its surface area : volume ratio? (Think of a balloon being blown up). How is this changing ratio related to cell division? ”

The surface area to volume ration decreases as cell division increases the size of the cell

”4. What is the function of mitosis in a cell that is about to divide? ”

To enable the chromosomal contents divide

”5. What would happen if mitosis were uncontrolled? ”

It would lead to uncontrolled growth

”6. How accurate were your time predictions for each stage of the cell cycle? ”

Very accurate

”7. Discuss one observation that you found interesting while looking at the onion root tip cells.”

The onion cells take considerably shorter time to undergo mitosis

Experiment 2: Tracking Chromosomes Through Mitosis

Once you have completed the digital exercise, select the “Results Table” button at the bottom right-hand corner of the screen and select the “Generate PDF” button at the top of the following screen. Insert your download into this document by selecting the Insert > Object > Text from file. Resize if necessary.

Post-Lab Questions

1. How many chromosomes were present before mitosis?

2

1. How many chromosomes did each of the daughter cells contain after mitosis?

4

1. Cite an example of a type of cell that undergoes mitosis. Why is it important for each daughter cell to contain information identical to the parent cell?

Human stem cells. To preserve genetic composition

1. Human skin cells divide at a higher rate than neurons (nerve cells). Hypothesize why this may be.

Due to the presence of chromosomes

1. Hypothesize what would happen if the sister chromatids did not split equally during anaphase of mitosis.

It may lead to abnormally large cells

Experiment 3: Following Chromosomal DNA Movement through Meiosis

Part 1: Once you have completed the digital exercise, select the “Results Table” button at the bottom right-hand corner of the screen and select the “Generate PDF” button at the top of the following screen. Insert your download into this document by selecting the Insert > Object > Text from file. Resize if necessary.

Parts 2, 3, and 4: Once you have completed the digital exercise, select the “View Data Table” button at the bottom left-hand corner of the home screen. Review your table. If you would like to make any changes, select the “Return” button in the bottom right-hand corner. If you are satisfied with your answers, select the “Generate PDF” button at the top of the screen. Insert screenshots below. Resize if necessary:

Post-Lab Questions

How did crossing over affect the genetic content in the gametes? Use your results to support your answer.

Crossing over ensures that daughter cells have equal genetic make up

What is the ploidy of the daughter cells at the end of meiosis I? What about at the end of meiosis II?

Diploid. At the end of meiosis II the daughter cells become haploid

List two differences between meiosis I and meiosis II.

In meiosis I homologous chromosomes are separated while in meiosis II sister chromatids separate. Meiosis I produce 2 diploid daughter cells while meiosis II produce 4 haploid daughter cells.

Based on your observations in the digital exercise, what can you conclude about the severity of nondisjunction that occurs in meiosis I as opposed to meiosis II?

It can lead to chromosomal abnormality

Why is it necessary to reduce the number of chromosomes in gametes, but not in other cells?

Because of the fusion of gametes which will restore chromosomal number

Blue whales have 44 chromosomes in every cell. Determine how many chromosomes you would expect to find in the following: ”

”Sperm Cell: ” 22

”Egg Cell: ” 22

”Daughter Cell from Mitosis: ” 44

”Daughter Cell from Meiosis II: ” 22

Experiment 4: The Importance of Cell Cycle Control

Data:

1. avoid chromosomal disconnection 2. Ensure completion of DNA replication 3. Prevent damage to cell structures 4. To prevent uncontrolled growth 5. To prevent development of tumors

Post-Lab Questions

”1. Record your hypothesis from Step 1 in the Procedure section here. ”

The daugher cells will be haploid

”2. What do your results indicate about cell cycle control? ”

It is important to avoid cell defects

”3. Suppose a person developed a mutation in a somatic cell which diminishes the performance of the body’s natural cell cycle control proteins. This mutation resulted in cancer yet, but was effectively treated with a cocktail of cancer-fighting techniques. Is it possible for this person’s future children to inherit this cancer-causing mutation? Be specific when you explain why or why not. ”

No. The offspring will not inherit somatic cells

”4. Why do cells which lack cell cycle control exhibit karyotypes which look physically different than cells with normal cell cycle. ”

Due to chromosomal mutations

”5. What are HeLa cells? Why are HeLa cells appropriate for this experiment? ”

They are cervical cancer cells therefore appropriate because they are immortal

”6. Research the function of the protein called p53. What does this function do? Explain how it can affect cell cycle control. ”

This is a tumor suppressor protein involved in preventing the development of tumors

”7. What is the Philadelphia chromosome? How is this chromosome related to cancer? Identify how this chromosome appears physically different on a karyotype than it appears on a karyotype of normal chromosomes. ”

Philadelphia chromosome results from chromosomal translocation and results to the development of acute myeloid leukemia. It therefore appears different on a karyotype.