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Mitosis, Meiosis and Fertilization

Newer Version Available

The activity below has a new and improved version available as two separate handouts; this older version is available as an archive to teachers still using it. Please find the new version at: Mitosis - How Each New Cell Gets a Complete Set of Genes and Meiosis and Fertilization – Understanding How Genes Are Inherited.



In the  hands-on activity, Mitosis, Meiosis and Fertilization, students use model chromosomes to simulate the processes of mitosis, meiosis and fertilization, and they answer questions designed to promote understanding of these processes. To demonstrate the principle that genes are transmitted from parents to offspring through the processes of meiosis and fertilization, students follow two alleles of a gene through gametes to zygotes as they model meiosis and fertilization. Students also learn how a mistake in meiosis can result in Down Syndrome.

Download Student Handout: PDF format or Word format

Download Teacher Preparation Notes: PDF format or Word format

 The Teacher Preparation Notes provide instructional suggestions and background information and explain how this activity is aligned with the Next Generation Science Standards.

We invite comments on this Hands-On Activity and the accompanying Teacher Preparation Notes, including suggestions for other teachers who are planning to use the activity, useful preparatory or follow-up activities, additional resources or any questions you have related to the activity, or a brief description of any problem you might have encountered. If you have a relevant Word document you would like to have posted on this comments page, such as a version of the protocol you have used in your classroom, or if you would prefer to send your comments or questions in a private message, please write Ingrid Waldron at

See also a complete list of activities:
Hands-on Activities for Teaching Biology to High School and Middle School Students


Serendip Visitor's picture

requesting for the answer key

can you send to me the answer key of the student handout? thank you! :)

iwaldron's picture

New version and answer keys

Please see the updated versions available at /sci_edu/waldron/#mitosis and /sci_edu/waldron/#meiosis . To find out how to receive the answer key, please read the Teacher Preparation Notes available at these links.


iwaldron's picture

Beta Version of Revised Activity Available

We are revising this activity and have split the activity into two enhanced closely-linked activities:

  • Mitosis – How Each New Cell Gets a Complete Set of Genes
  • Meiosis and Fertilization – Understanding How Genes Are Inherited

Major enhancements include:

– more explicit links between genotype and phenotype

– more discussion of how meiosis and fertilization result in genotypic and phenotypic variation in offspring (with explicit discussion of independent assortment and crossing over).

Our current versions of the Student Handouts and Teacher Preparation Notes for these two new activities are available at . We will be particularly grateful for your comments and suggestions while we are in the pilot testing phase for these activities.


Serendip Visitor's picture

Rollosomes and Sockosomes

Could you please post a photograph of a rollosome and a sockosome? I love this activity idea, however I am having a hard time with creating the rollosome because I just can't quite picture it. Thank you.

iwaldron's picture

Picture of Rollosomes

I have included a picture of the rollosomes, as well as improved instructions for making rollosomes, on pages 3-4 of the newly revised Teacher Preparation Notes (available at the link above). Thanks for your inquiry which inspired these improvements.



Serendip Visitor's picture


hi all,

I am a graduate student working in the GK-12 program at University of Idaho. For this fellowship, I teach honors biology two days a week at a local high school. I really like the idea of this activity, and I actually created something similar for a cellular respiration unit I taught before Christmas. One suggestion I have is to include pictures of the actual model chromosomes/chromatids in the teacher notes. Being a visual person, the provided line drawing of the "rollosomes" was helpful, but I still think seeing an actual model in a set photos would be most useful in making the models.


Serendip Visitor's picture


Where is the drawing of the rollosomes?

iwaldron's picture

diagrams of rollosomes

The diagrams of the rollosomes are on page 4 of the Teacher Preparation Notes (see link above) and the instructions for making rollosomes are on pages 3-5.


iwaldron's picture

thanks for your suggestion

We appreciate your suggestion and will plan to implement your suggestion toward the end of 2014 when we will revisit this activity.


iwaldron's picture

2013 revision

The biggest change in the 2013 revision of this activity has been to incorporate the helpful suggestion from K. Harding to make the model chromosomes from hair roller curlers. This approach provides model chromosomes that are relatively easy to make, engaging for the students to use, and an appropriate size for classroom use and storage. In addition, the introductory section of the Student Handout has been clarified and streamlined, the format of the Student Handout has been improved to facilitate classroom use, and the Teacher Preparation Notes have been revised to clarify the instructions for making model chromosomes and to explain the relationship of this activity to national standards.

K. Harding's picture

Another material for models

I made the model chromosomes out of bendable hair rollers found at beauty supply stores. They come in a variety of widths and 9 5/8" lengths. I used 3/4" and 5/8" widths in two colors, gray and orange. They are easily cut with scissors for the foam and wire cutters for the wire core. I cut them into 5 7/8" and 3 3/4" lengths for the longer and shorter chromatids. I used permanent markers to add the stripes and for the alleles. Sticky back Velcro circles attached the sister chromatids together. I was also able to make it possible to demonstrate cross over by cutting off portions of the chromatids and reattaching them with Velcro circles. I made two sets of model chromosomes out of two packages of rollers. With 4 packages you could make 5 sets.

iwaldron's picture

thank you

Thank you very much for your very helpful, creative and practical suggestion.


iwaldron's picture

August, 2011 Revision

The Teacher Preparation Notes now include instructions for making model chromosomes from swim noodles or socks.  Sockosomes look like metaphase chromosomes in a karyotype and they are small enough for easy classroom use and storage, but they are relatively time-consuming to make.  Chromonoodles are relatively easy to make, but they are larger (up to 8" long).  If you want to make Chromonoodles, we recommend purchasing the needed swim noodles now during the summer swim season.  We have also made modest improvements in some of the questions in the Student Handout.  Also, a key is  now available upon request to

iwaldron's picture

January 2011 revisions

The Student Handout has been revised and reorganized to focus more on the key learning goals, improve the logical flow, and reduce redundancy and the length of the handout.  The Teacher Preparation Notes have also been revised, with additional information included.

iwaldron's picture

January 2010 revisions


The Student Handout has been reformatted for greater ease of classroom use, and the Teacher Preparation Notes have been clarified with  improved instructions for making the sockosomes and an expanded and improved section of instructional suggestions.


Serendip Visitor's picture


I've used this student packet for three years now and I love it. It does a great job of highlighting what is important and getting the point accross visually. I really liked the revisions. Thanks a ton.
Maya Heissenbuttel
North Pines Middle School
Central Valley School District
Spokane Washington

iwaldron's picture

May 2009 revision of this activity

The only changes in this version of the Student Handout and Teacher Preparation Notes are changes in the symbols used for some of the alleles on the sockosomes, in order to provide consistency with the symbols for alleles used in our genetics activities.
HappyGirl's picture

Mitosis Meiosis different

Here is an article discussing the difference between Mitosis and Meiosis

Anonymous's picture

Using sockosomes to assess understanding of mitosis and meiosis

A lively discussion group among Philadelphia high school biology teachers ( has lots of helpful suggestions, including using sockosomes to have students make a stop-animation movie to demonstrate their understanding of mitosis and meiosis.

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