Download Mitosis and Meiosis Pipe Cleaner Simulation: Crossing

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Resource ID#: 63364
Mitosis and Meiosis Pipe Cleaner Simulation: Crossing
Over and Independent Assortment
This lesson requires the students to simulate the movement of chromosomes during mitosis and meiosis using different-colored pipe cleaners. The
pipe cleaners allow the instructor to highlight both recombination (crossing over) and independent assortment, two important components of meiotic
cell division. The processes that create variation among gametes are also emphasized.
This lesson plan includes excellent teacher support in the form of videos that explain how the pipe cleaners should be manipulated to demonstrate
the concepts of mitosis, meiosis, and independent assortment.
Subject(s): Science
Grade Level(s): 9, 10, 11, 12
Intended Audience: Educators
Suggested Technology: Document Camera,
Computer for Presenter, Internet Connection,
Overhead Projector
Instructional Time: 1 Hour(s) 30 Minute(s)
Freely Available: Yes
Keywords: meiosis, mitosis, reproduction, recombination, crossing over, independent assortment, chromosomes,
genetic variation
Instructional Design Framework(s): Demonstration, Cooperative Learning
Resource Collection: CPALMS Lesson Plan Development Initiative
ATTACHMENTS
Independent Assortment04112014.mp4
Meiosis04112014.mp4
Mitosis_04112014.mp4
LESSON CONTENT
Lesson Plan Template: General Lesson Plan
Learning Objectives: What should students know and be able to do as a result of this lesson?
After this lesson, students will be able to:
1. Show the process of mitosis and meiosis, specifically how the chromosomes are arranged during each step.
2. Identify where genetic variation is generated during meiosis, and contrast this with mitosis, in which genotype and phenotype are conserved.
3. Describe the process of crossing over during meiosis; identify when this occurs and how it generates genetic variation.
4. Explain the phenomenon of independent assortment; explain how this leads to genetic variation among an individual's gametes.
5. Explain why and give examples of processes where the two types of cell division are required: mitosis for when cells must be duplicated exactly (growth, cell
replacement, asexual reproduction), and meiosis for when cell chromosome number must be halved (sexual reproduction).
Prior Knowledge: What prior knowledge should students have for this lesson?
Students should know:
page 1 of 4 1. the basics of sexual reproduction (two gametes unite to form a zygote during fertilization). Students should also know the basics of asexual reproduction (e.g.,
budding in yeast).
2. what DNA is, that it is contained in chromosomes found in the cell nucleus, and that it contains the genetic information in cell.
3. that in a diploid organism like humans, chromosomes are arranged in homologous pairs. The two chromosomes in a homologous pair contain the same set of
genes, but different sets of alleles. One chromosome in a homologous pair was inherited from the mother, and one was inherited from the father.
Guiding Questions: What are the guiding questions for this lesson?
1. What are processes in which genetic material needs to be copied exactly during cell division, that is, when must cell division produce identical daughter cells? In
these cases, how do the chromosomes move so that each daughter cell is identical?
Answer: growth, development, cell replacement, and asexual reproduction. Chromosomes are duplicated then sister chromatids are separated to either side of the
cell.
2. Are there any processes involving cell division where daughter cells do not have to have the exact same genetic material as their parents? In fact, are there any
processes where daughter cells must be different from their parents, but they still end up with the same set of genes?
Answer: Yes, sexual reproduction. The chromosome number must be halved or children would end up with 2x the chromosome number as their parents.
3. In cases where genetic variation is required (i.e., sexual reproduction), where during the process of cell division is it generated?
Answer: During crossing over and recombination.
Teaching Phase: How will the teacher present the concept or skill to students?
1. The teacher will first show On Down -- Down Syndrome, a video about Down syndrome from VCU Life Sciences. Down syndrome occurs when there are three
copies of chromosome 21 in each cell. This example will show what happens when errors occur during cell division.
The teacher will then bring up other types of disorders that occur due to errors in meiosis and mitosis, such as mosaicism (Turner's syndrome), monosomy, etc. This
will get the students thinking about why cell division must result in a complete set of genetic information.
2. The teacher will then review processes in which an organism must copy its cells exactly during cell division: growth, development, cell replacement, and asexual
reproduction.
3. The teacher will pass out the pipe cleaners: each student gets two pink, two red, two light blue, and two dark blue. The teacher will explain what the pipe cleaners
represent: two pairs of homologous chromosomes (red/pink and blue/light blue). Starting with a nucleus with four chromosomes (one of each color), the students'
challenge is to come up with a method of moving the chromosomes during cell division so that the end result is two daughter cells with exactly this set of
chromosomes.
4. Using his or her own set of pipe cleaners, the teacher will then demonstrate the process of mitosis. The teacher will identify each step as it occurs, starting with
DNA replication, then proceeding to mitosis (prophase, metaphase, anaphase, and telophase/cytokinesis). A video that demonstrates how the chromosomes should be
moved has been included; see Mitosis_04112014.mp4 in the Uploaded Files section.
5. After students simulate mitosis on their own, the teacher will point out that everyone's daughter cells are exactly the same - re-emphasize that mitosis creates
exact copies of parent cells.
6. The teacher will then discuss with the class and review processes in which an organism does not copy its genetic material exactly during cell division (i.e., sexual
reproduction). The students' challenge is then to devise a method that halves chromosome number during cell division.
7. Using the pipe cleaners, the teacher will show the movement of chromosomes during meiosis. They will identify each step as it occurs, starting with DNA
replication, then proceeding to meiosis (prophase I and II, metaphase I and II, anaphase I and II, and telophase I and II /cytokinesis). Introduce crossing over during
prophase I by cutting off the ends of two pipe cleaners in a homologous pair and exchanging them (securing them to the opposing chromosome end). A video that
demonstrates how this should be executed has been included; see Meiosis-04112014.mp4 in the Uploaded Files section.
8. The teacher will then have the students simulate meiosis on their own, drawing/labeling the different stages. The teacher should not insist that the students follow
him or her exactly in regards to how the homologous pairs are lined up (although, red and pink should still be next to one another; the same with blue and light blue).
This is critical for generating variation among the students' gametes. A video explaining this concept has been included; see Independent Assortment-04112014.mp4
in the Uploaded Files section.
9. After the students simulate meiosis on their own, have them compare their resulting gametes. Ask/discuss how the gametes are different from the parent cell (half
the chromosome number, recombined chromosomes). Ask/discuss how the gametes are different from one another (different combinations of chromosomes).
10. Finally, the teacher should return to the concepts introduced in the initial video: if Down syndrome and other disorders arise from errors in cell division,
when/where do these errors occur? This will introduce the last challenge - the teacher will provide the students with three types of genetic disorders that may occur
from errors in meiosis (see below). The students must figure out where in meiosis an error occurred that resulted in these problematic outcomes. Discussing the
symptoms of each outcome will reinforce why meiosis must result in exactly half the genetic material of the parent cell.
a. Trisomy - 3 chromosomes of one type (for example, in Down syndrome, caused by trisomy of chromosome 21) - nondisjunction of chromosomes during either
Anaphase I or Anaphase II
b. Monosomy - 1 chromosome of 1 type (for example, Turner syndrome, caused by monosomy of the X chromosome) - nondisjunction of chromosomes during either
Anaphase I or Anaphase II
c. Reciprocal translocation - the switching of the ends of two non-homologous chromosomes (for example, Chronic Myelogenous Leukemia, caused by a translocation
of the ends of 9 and 22) - during recombination
Guided Practice: What activities or exercises will the students complete with teacher guidance?
The students will answer a series of guided discussion questions about processes that involve cell division, specifically which processes require that the genetic
material of the parent cell be copied exactly.
The students will also perform mitosis and meiosis with their pipe cleaners while being guided by the teacher.
Independent Practice: What activities or exercises will students complete to reinforce the concepts and skills developed in the
lesson?
Using their pipe cleaners, the students will come up with methods of cell division that either retain or halve the chromosome number of the parent cell.
Using their pipe cleaners, the students will go through mitosis and meiosis on their own, drawing each stage.
The students will independently figure out where errors in meiosis occurred that lead to genetic disorders.
page 2 of 4 Closure: How will the teacher assist students in organizing the knowledge gained in the lesson?
The teacher will return to the questions posed at the beginning of the lesson in order to reflect on the knowledge gained. Through discussion, the teacher will review
with the class how/why genetic material is copied exactly in mitosis, but halved during meiosis. The class will also review the sources of genetic variation in meiosis.
Summative Assessment
The students will perform meiosis and mitosis on their own, during which the teacher can assess whether their method is correct.
Near the end of the activity, the teacher will present the students with examples of human disorders that result from errors in cell division. Using their chromosomes,
the students will have to determine where in the process of mitosis or meiosis the errors occurred.
At the end of the activity, the teacher will return to the questions originally presented. The students will be assessed based on their answers to these questions.
Formative Assessment
The lesson will start with a series of questions about the role of cell division during an organism's development and reproduction. When organisms grow by dividing
cells, do new cells need the same number of chromosomes? The exact same set of genes? What about when organisms replace old cells? What about when
organisms reproduce (sexually vs. asexually)? Why might variation be good in the new cells when reproducing? This will establish what the students understand about
the conservation of chromosome number and genetic material during mitosis vs. meiosis.
Using pipe cleaners, the students will simulate the movement of chromosomes during mitosis. On their own, they will design a way to divide a cell so that the two
daughter cells are both identical to the parent cell. The teacher will be able to refer back to this while going through what actually occurs during mitosis.
Later, after using pipe cleaners to model how the chromosomes actually move during mitosis and meiosis, the teacher will circulate around the room while the
students do it themselves. The teacher can correct any misconceptions. Importantly, the teacher should note variation in the students' final gamete types. This will
allow him or her to introduce the concept of independent assortment later in the lesson.
Feedback to Students
Students will initially work in pairs and will get feedback from both their peers and their teacher as they design a method of cell division that makes two identical
copies of a cell. It will be immediately apparent if their method does not work, and their teacher/peer can help them adjust their method.
While the students are going through mitosis and meiosis with their own pipe cleaners, they will receive feedback from the teacher and their peers; there will be time
for them to restart their simulation if they do it improperly.
ACCOMMODATIONS & RECOMMENDATIONS
Accommodations: Some students may need a larger set of pipe cleaner chromosomes to accommodate for visual impairments or difficulty with motor skills; use
the entire pipe cleaner instead of cutting it initially.
Some students may need to review basic genetics concepts before the lesson (inheritance, reproduction, chromosome structure).
Selected pairing may help students with difficulties by providing the opportunity for valuable peer feedback.
Extensions: If they have cell phones or tablets, the students can take pictures of each stage to be used later. The students should also be encouraged to take their
pipe cleaner sets home to practice each type of cell division on their own.
This lesson can be paired with a lesson on Mendelian inheritance or Punnett squares. The pipe cleaners explicitly show the law of segregation, because the two
chromosomes in a homologous pair end up in different gametes during meiosis. They also show the law of independent assortment, as described above. Gametes from
two different meiotic events (i.e., a mother and a father) can be paired to show fertilization, and the possible outcomes of mating (i.e., a different way of showing the
Punnett square).
Finally, mathematics can be integrated into this lesson by calculating the number of possible gamete types from one individual. The number of different combinations of
chromosomes in the products of meiosis is 2N, where N is the number of homologous pairs of chromosomes. This means for humans, since N = 23, and 223 is
8,388,608, one person can produce over 8 million types of gametes. Since sexual reproduction combines gametes from two individuals, we multiply 223 by 223, which
means that there are 64 trillion possible offspring genotypes that may result from any two parents. (2N), where N is the number of homologous chromosome pairs.
Suggested Technology: Document Camera, Computer for Presenter, Internet Connection, Overhead Projector
Special Materials Needed:
For each student, you need 4 chenille pipe cleaners (12 in. x .23 in.) - each should be a different color. The activity works best if you use two pairs of similar colors,
such as pink and red, dark blue and light blue. Each pipe cleaner will represent a separate chromosome. Each pipe cleaner should be cut in half to make two copies of
each color.
Each 1-2 students also needs a pair of scissors.
SOURCE AND ACCESS INFORMATION
Contributed by: David McNutt
Name of Author/Source: David McNutt
District/Organization of Contributor(s): Florida State University
Is this Resource freely Available? Yes
page 3 of 4 Access Privileges: Public
License: CPALMS License - no distribution - non commercial
Related Standards
Name
SC.912.L.16.14:
SC.912.L.16.16:
SC.912.L.16.17:
Description
Describe the cell cycle, including the process of mitosis. Explain the role of mitosis in the formation of new cells and its
importance in maintaining chromosome number during asexual reproduction.
Describe the process of meiosis, including independent assortment and crossing over. Explain how reduction division
results in the formation of haploid gametes or spores.
Compare and contrast mitosis and meiosis and relate to the processes of sexual and asexual reproduction and their
consequences for genetic variation.
Remarks/Examples:
Annually assessed on Biology EOC. Also assesses SC.912.L.16.8 SC.912.L.16.14 SC.912.L.16.16.
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