Download Columbia College Biology 110 Laboratory Manual

Columbia College
Biology 110 Laboratory Manual
LABORATORY EXERCISE 3 – MITOSIS AND MEIOSIS
Objective:
1) To understand the principles behind mitosis and meiosis.
1) Mitosis
The following materials are available to help you understand the process of mitosis. You do
not need to go through all of them, but use as many of the materials as is necessary to help
you understand the process.
-
Photographic microslides – booklets numbered 53 and 55
-
Demonstration slides
Study the demonstration showing the various phases of mitosis under the microscope. Do
not move the slide as this changes the position of the section under focus for the next person.
Use the fine adjustment only if you need to get a sharper focus. Make note specifically of
various characteristics of each phase, as you need to be able to recognize each one.
Take the slides labeled onion root tip (Allium) and whitefish or Ascaris and locate the
various phases of mitosis under the compound microscope.
Q1. What is the purpose of mitosis?
Q2. Draw the following stages of mitosis (early interphase, late interphase, prophase,
metaphase, anaphase and telophase) in the space below in a cell whose diploid
number is 8. Each chromosome should be easily distinguished and each diagram
should be adequately labeled.
Q3. What events in mitosis ensure that each daughter cell gets an identical set of
chromosomes?
Q4. What would happen if arbitrary separation of chromosomes occurred during
mitosis?
2) Meiosis
The following materials are also available to help you understand the process of meiosis.
You do not need to go through all of them, but use as many of the materials as is necessary
to help you understand the process.
-
Photographic microslides – booklet numbered 92
-
Demonstration slides
Study the demonstration showing the various phases of meiosis under the microscope. Do
not move the slide as this changes the position of the section under focus for the next person.
Use the fine adjustment only if you need to get a sharper focus. Make note specifically of
various characteristics of each phase.
Take the slides labeled Lillium anther and grasshopper testis and locate the various phases of
meiosis under the compound microscope.
Q5. What is the purpose of meiosis?
Q6. If a diploid parent cell has 50 chromosomes (2n = 50), answer the following two
questions for each of the cell types below:
1) the number of chromosomes
2) the number of DNA molecules
a) A cell at prophase of mitosis?
b) A cell at prophase I of meiosis?
c) A cell at anaphase of mitosis?
d) A cell at anaphase I of meiosis?
e) A cell at prophase II of meiosis?
f) A cell at anaphase II of meiosis?
Q7. Referring to the same cell from the previous question, how many homologous pairs
of chromosomes would there be in the following cell types:
a) A cell at prophase of mitosis?
b) A cell at prophase I of meiosis?
c) A cell at prophase II of meiosis?
d) A cell at anaphase of mitosis?
e) A cell at anaphase II of meiosis?
Q8. How many genetically different cells can possibly be formed (not including crossing
over) when a diploid cell with 44 chromosomes undergoes meiosis?
Q9. Explain how it is possible for a human cell to have 44 autosomes and XXY sex
chromosomes.
Q10. If 2N = 8, show how chromosomes align at the metaphase plate:
a) During mitosis.
b) During the first division of meiosis.
c) During the second division of meiosis.
d) Explain, using diagrams, how many genetically different daughter cells are
possible in a cell with 2N = 8 undergoing meiosis.