Chapter 10.4 Lab: Meiosis and Introduction to Karyotyping
Learning Objectives
During this lab you should be able to:
1. Develop a basic understanding of the stages of meiosis
2. Identify the stages of meiosis from a virtual lab viewing cells in meiosis
3. Develop an understanding of how alleles(genes) recombine during meiosis
4. Introduction to basic karyotyping
Introduction
Meiosis is the second important kind of nuclear division. It resembles mitosis in many ways but the consequences of
meiotic divisions are very different from those of mitotic divisions. While mitotic division may occur in almost any living
cell of an organism, meiosis occurs only in special cells. In animals, meiosis is restricted to cells that form gametes (eggs
and sperm). Each species has a characteristic number of chromosomes per somatic cell. Fruit flies have 8; normal humans
have 46. They exist as homologous pairs (partners) that are similar in size and shape and carry the same kinds of genes.
Thus humans have 23 homologous pairs. The full complement of 46 chromosomes is referred to as the diploid
number (referring to the fact that each kind of chromosome is represented twice).
In higher organisms when an egg is fertilized the egg and sperm fuse to form a single cell called a zygote which develops
into a new organism. If the egg and sperm were both diploid (46 chromosomes each in the case of humans) then the
resulting zygote would be tetraploid. This would be an intolerable situation, so a mechanism has evolved to insure that
each gamete (egg or sperm) contains only one representative of each homologous pair (or half the diploid number). This is
referred to as the haploid number.
Haploid Egg + Haploid Sperm = Diploid Zygote
The mechanism that makes this possible is meiosis. Meiosis consists of two divisions, Meiosis I and Meiosis II, and can
potentially result in the production of four cells. However the DNA is only synthesized once (prior to Meiosis I). The
duplicating of DNA occurs during Interphase just as it does in a typical somatic cell. The difference is the cell then enters
the meiotic phase. The subdivisions of meiosis are named like the subdivisions of mitosis (prophase, metaphase,
anaphase, telophase) but as we shall see the events are somewhat different.
Summary of Meiosis
Part A: Understanding the Stages of Meoisis
As mentioned before meiosis is very similar to mitosis and consists of the same or similarly named stages, Prophase,
Metaphase, Anaphase, and Telophase. However, Meiosis as mentioned involves two divisions. During this section of the
lab, as you did with the mitosis lab, you will develop ideas based on the images of the meiotic phases below. Because you
already have a general idea of what is taking place from mitosis, this should be easy! Interphase is the exact same for both
mitosis and meiosis, it is simply a period of growth and DNA replication.
Describe what is happening with the following organelles in each of the stages of the cell cycle below. You will use this
during the analysis section to form your understanding of what is taking place and why during each stage. Include the
following information for each organelle.
Nucleus - Present/Partially Present/Not Present
Chromosomes- Location, condensed/uncondensed, appear as chromosomes or sister chromatids, movement (if any), Any
color differences (recombination) ASK FOR HELP!
Centrioles - Present/Not present
Mitotic Spindle - Present/Not present
Cleavage Furrow - Present/Not Present
Meiosis I
Prophase I
Metaphase I
Anaphase I
Telophase I
Nucleus ___________
Chromosomes:
Nucleus ___________
Chromosomes:
Nucleus ____________
Chromosomes:
Nucleus ____________
Chromosomes:
Centrioles ___________
Centrioles __________
Centrioles ____________
Centrioles __________
Mitotic Spindle ________
Mitotic Spindle ________
Mitotic Spindle _________
Mitotic Spindle ________
Cleavage Furrow __________
Cleavage Furrow __________
Cleavage Furrow ________
Cleavage Furrow _______
Other Observations:
Other Observations:
Other Observations:
Other Observations:
Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II
Note: Notice the difference in the sister chromatids/chromosomes in the cells
Prophase II
Metaphase II
Anaphase II
Telophase II
Nucleus ___________
Chromosomes:
Nucleus ___________
Chromosomes:
Nucleus ____________
Chromosomes:
Nucleus ____________
Chromosomes:
Centrioles ___________
Centrioles __________
Centrioles ____________
Centrioles __________
Mitotic Spindle ________
Mitotic Spindle ________
Mitotic Spindle _________
Mitotic Spindle ________
Cleavage Furrow __________
Cleavage Furrow __________
Cleavage Furrow ________
Cleavage Furrow _______
Other Observations:
Other Observations:
Other Observations:
Other Observations:
Part B: Observing Cells Undergoing Meoisis
During this section of the lab, you will be viewing cells that our going through meoisis, however instead of using prepared
slides you will be doing a virtual lab online. This lab can be done on a chromebook or the desktop computers at your lab
station (preferred). You and your partner can do this section together. This virtual lab will also reinforce some of the
information covered in Part A.
To complete this section go to the following website:
http://bio.rutgers.edu/~gb101/lab10_meiosis/meiosis_web/index10.html
1. Follow the directions on the website. Read the introduction (familiar huh?!) and click on the Begin Assignment tab.
2. Ignore Part 1, that's what we just did!
3. Part 2 will walk you through the part of the virtual lab we are interested in. Read the directions and follow each of the
steps outlined on the website. Click the "Click here to being" tab at the top.
4. Click on a section of the lily pollen sac to view meiotic cells. You may look at several different sections of the sac!
Choose a cell and identify which stage of meoisis I that cell is in. (Ignore the early/late phases and interkinesis)
5. Once you choose the correct answer draw the cell in the appropriate space below.
Prophase I
Metaphase I
Anaphase I
Telophase I
6. Repeat steps 4 and 5 for Meoisis II. You will have to clock on the "Here" tab on the right to get to the cells that are in
meiosis II. Again draw a cell in each phase.
Prophase II
Metaphase II
Anaphase II
Telophase II
PART C: Karyotyping
Karyotyping is a process in which cell biologists look at the different genes/alleles on chromosomes and create a "map"
for an organisms set of homologous chromosomes. We will discuss this in much more detail at the beginning of the
genetics chapter next week. This will introduce you to some of the general ideas about human karyotypes.
Human Karyotypes
Procedure:
1. Using the same virtual lab website, move on to Part 4.
2. Follow the directions for Part 4, I will be around to help you, this is just to introduce you to some of the things we will
discuss in genetics and give you an idea of what recombination is (as mentioned during Part A of your lab)
3. Write your answers to each of the cases in the spot below!
Case 1
Case 2
Case 3
Case 4
Case 5
Case 6
Case 7
Case 8
4. Read about non-disjunction and give a quick summary in your own words of what happens when this occures during
meiosis and why it is bad for a cell.