BIO-110 Lab: Mitosis and Meiosis

Submission Instructions

Type your answers and paste any required pictures directly into this Word document. Submit it via the Blackboard submission link in Word format (docx).

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Objectives:

1. Students will describe the cell cycle and mitosis, including stages and phases.

2. Students will compare and contrast the processes of mitosis and meiosis.

3. Students will identify the differences in the behavior of homologous chromosomes in meiosis and mitosis.

Introduction

Cell division is the process where a parent cell divides and gives rise to two or more daughter cells. Generally, this process involves two steps:
karyokinesis (nuclear division) and
cytokinesis (cellular splitting). During
mitosis, the parent cell duplicates and donates its genetic information to its daughter cells. Single cellular organisms utilize this technique for reproduction. Multicellular organisms use mitosis for growth and repair. This ensures genetic similarity between the parent and daughter cells.
Meiosis, however, is a bit distinct. Eukaryotic
diploid (2n) cells duplicate their DNA and experience two rounds of cytokinesis. This process halves their chromosomal number forming
haploid (n) sex cells or gametes. Upon fertilization (fusion of gender dissimilar gametes), these haploid gametes combine to form a diploid (2n) zygote. Therefore, meiosis ensures that the next generation of individuals will have a combination of traits different form each parent. By familiarizing ourselves with these two cycles, we can appreciate the complexity of cellular development.

Procedure

Complete Activities I-III below.

ACTIVITY 1: CELL CYCLE

Answer questions #1-5 about the diagram and the information it portrays
(2 points each).

1. Explain the relationship between the cell cycle and apoptosis.

2. List the two major phases that make up the entire cell cycle. Underline the phase that is longest (i.e. makes up the largest portion of the cell cycle).

3. List the phases of Interphase in the order they occur. In which of these phases does DNA replication take place?

4. According to your textbook, what happens during Gap-1 (G1)? Synthesis (S)? Gap-2 (G2)?

5. List the phases of mitosis in the order they occur. What event occurs after mitosis, but before interphase?

6. After cytokinesis is complete, each daughter cell begins what stage of Interphase?

ACTIVITY 2: MITOSIS

Complete Parts I, II, and III below.

Part I: Fill-In

For each event, indicate whether it takes place in Prophase, Metaphase, Anaphase, or Telophase by writing P, M, A, or T on the line
(1 point each).

7.
Cleavage furrow is most visible.

8.
Chromatin condenses into chromosomes.

9.
Centromeres break down and sister chromatids become daughter chromosomes.

10.
Nuclear envelope breaks down.

11.
Occurs immediately prior to cytokinesis.

12.
Daughter chromosomes arrive at the poles.

13.
Chromosomes line up single file along the cell’s equator.

14.
Occurs immediately after Gap-2.

Part II: Whitefish Embryo Micrographs

Whitefish embryos are commonly used to study mitosis due to their rapid rate of cell division and transparent cells. The images provided below are photographs of developing whitefish cells. For each image, sketch the cell that is highlighted and identify the stage that the cell is in (on the next page). Please label chromosomes within your sketch
(4 points each). Special thanks to Shannan Muskopf from
Biology Corner (link opens a new window) for use of these images.

Revised Spring 2024

Figure 1: Whitefish Blastula

Figure 2: Whitefish Blastula

Figure 3: Whitefish Blastula

Figure 4: Whitefish Blastula

Part II: Whitefish Embryo Sketches

Place your sketch for Figure 1 here. Which phase of mitosis is this? ___________________________________

Place your sketch for Figure 2 here. Which phase of mitosis is this? ___________________________________

Place your sketch for Figure 3 here. Which phase of mitosis is this? ___________________________________

Place your sketch for Figure 4 here. Which phase of mitosis is this? ___________________________________

Part III: Onion Root Tip Micrographs

Onion root rips are often used in mitosis lesson, because they contain actively dividing cells in the root meristem (tip). These root tips were stained with dyes to increase their chromosomes’ contrast. For each image, sketch the cell that is highlighted and identify the stage that the cell is in (on the next page). Please label chromosomes within your sketch
(4 points each). Special thanks to Shannan Muskopf from
Biology Corner (link opens a new window) for use of these images.

Revised Spring 2024

Figure 1: Onion Root Tip

Figure 2: Onion Root Tip

Figure 3: Onion Root Tip

Figure 4: Onion Root Tip

Part III: Onion Root Tip Sketches

Place your sketch for Figure 1 here. Which phase of mitosis is this? ___________________________________

Place your sketch for Figure 2 here. Which phase of mitosis is this? ___________________________________

Place your sketch for Figure 3 here. Which phase of mitosis is this? ___________________________________

Place your sketch for Figure 4 here. Which phase of mitosis is this? ___________________________________

ACTIVITY 3: COMPARISON OF MEIOSIS AND MITOSIS

Complete part I below.

Part I: Short Answer

Use your textbook to answer each question about the cell cycle
(3 points each).

1. How do sexual and asexual reproduction differ from one another?

1. Where does meiosis occur in the body? Where does mitosis occur?

1. What are autosomes, and what are sex chromosomes?

1. Summarize the major events that occur curing mitosis and cytokinesis.

1. Compare and contrast mitosis and cytokinesis in plant and animal cells.

1. Explain what is meant by the term homologous chromosomes.

1. Why is meiosis called a “reduction division”?

1. Describe the process of meiosis I. Accurately include following terms within your answer to receive full credit: chromosome sets (per cell) at the beginning, chromosome sets (per cell) at the end, homologous chromosomes, spindle fibers, and crossing over.

1. Describe the process of meiosis II. Accurately include following terms within your answer to receive full credit: chromosome sets (per cell) at the beginning, chromosome sets (per cell) at the end, homologous chromosomes, sister chromatids, spindle fibers.

1. Describe the process of independent assortment and random orientation. How does it increase genetic variability in gametes?

1. What is the difference between a gamete and a zygote?

1. What is crossing over, and how does it introduce genetic variation? In what phase does it occur?

1. Compare and contrast the outputs of meiosis and mitosis with regard to the number of cells and the chromosome complement of each cell.

1. From an evolutionary standpoint, why is sexual reproduction advantageous for the continuation of a species?