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LESSON II:
ASEXUAL REPRODUCTION AND MITOSIS
PART B
To Address NYS Standards:
2 (Organisms inherit genetic information in a variety of ways that result in continuity of
structure and function between parents and offspring) and 4 (The continuity of life is
sustained through reproduction and development).
Behavioural Objectives:
By integrating the ideas from Lesson I, the students will be able to accurately explain
how mitosis can be used for reproduction by single-celled organisms. The students will
also learn all vocabulary and chromosome concepts necessary to completely understand
the outcome of mitosis and the various stages.
Explanation of Lesson Plan:
This lesson will build upon the mitosis concepts in Lesson I, and will introduce mitosis as
a means of asexual reproduction. It is hoped that by introducing a new use for mitosis
along with further information on the process, that students’ interest will be kept. More
detail on each stage of mitosis, as well as the various apparatuses and structures involved
will be given.
Hook: (3 minutes)
“So last time we saw the basic idea of mitosis. We want to make two identical cells. We
know the basic route that we need to take, but we don’t know all the whimsical little parts
along the way. What else, aside from chromosomes, do you think that we need to dance
the dance of mitosis?”
Test of Prior Learning: (5 minutes)
1. What are the five stages in the cell cycle?
2. What does mitosis produce?
3. Why do you think that mitosis is a good process for single-celled organisms to use to
reproduce?
New Learning: (30 minutes)
1. All sorts of microorganisms use mitosis to reproduce. You don’t need a partner to
dance this dance! Yeast, bacteria, archea, protists, etc.
2. Bacteria use binary fission. The are prokaryotes, so they have no nucleus. They have
a long, circular bit of DNA. It’s not really a chromosome, as it has no associated histone
proteins, and it’s not packaged up nicely. (some archea have histones, still circular)
3. Yeast bud to reproduce. They start growing a bud, and it eventually pops off. Not
even splitting.
4. Spores are formed by fungi and molds.
5. Sea stars can regenerate lost limbs
6. We now need to look at each step more closely. Let’s look at a cell in each stage.
- Handout of cells in each stage will be labeled by students and stapled into
workbook.
7. The spindle apparatus is formed from the centrosomes. It is made out of
microtubules. The spindle fibres push and pull on the chromosomes and on each other to
drive the dance.
8. Prophase is where the centrosomes migrate to opposite poles of the cell, and
chromosomes condense. Let’s look more closely at the chromosomes.
9. They are coiled and coiled and coiled, with histone proteins. The center is a
centromere, where the microtubules attach.
10. Duplicated chromosomes have two chromotids. THEY ARE EXACT COPIES.
EACH ONE CONTAINS A COMPLETE SET OF LOCI FOR THE ENTIRE
CHROMOSOME. Separating them will give each daughter cell one complete copy,
then.
11. Metaphase is where the chromosomes line up on the metaphase plate, or the equator
of the cell. Each duplicated chromosome has one chromatid on each half of the cell.
12. Anaphase is when the sister chromatids are separated, and move towards opposite
poles of the cell.
13. Telophase is when the nucleus starts to reform, and the cell membrane pinches into
two separate cells, in a process called cytokinesis. What do bacteria and plants have to do
here, as well? Form the cell wall with a cell plate.
14. The cell cycle in an average onion root tip cell takes about 22 hours:
17.23 hours are spent in interphase
3.12 hours in prophase
.55 hours in metaphase
.92 hours in anaphase and
.18 hours in telophase
Test of New Learning:
1. Pool Noodles will be used to “act out” the dance of mitosis, with some sort of snazzy
waltz in the background. Two students will manipulate the four noodles, and another
student will be the narrator. Strings will be provided for spindle fibres.
Assignment:
Pg. 411: 20-2, 1, 2, 5; Pg. 415: 20, 23, 24