Lesson 2 of 2
Objective: Students will design a model that shows meiosis in a healthy cell.
In this lesson, students will use chromonoodles to create a meiosis model. They will explore several scenarios of abnormal nuclear division in order to understand how certain chromosomal disorders occur. Finally, they will present their stop-motion videos. Here is an overview of what students will learn today.
This activity is best done in a large room such as a gym. Students should work in groups. For this activity, each lab group will need the following equipment:
- Four pairs of homologous chromonoodles
- A pile of yarn the same color as the chromonoodles
- 4 equal pieces of tow rope
- 8 equal pieces of yellow seine twine
- 8 equal size pieces of white seine twine
- 4 small twisted pool noodles
Students should work in groups of four for this activity. They can use this student handout for directions. (Note: I typically walk student through the first portion of this activity to eliminate confusion.)
Part One: Creating the Sex Cells
First, they should make a cell membrane with the tow rope and a nuclear membrane with the yellow seine twine. Next, they should place the pile of colored yarn inside the nucleus. Students should place twisted pool noodles in the nucleus and then remove pile of colored yarn and insert pool noodles. Next, students should remove the yellow seine twine. They should add the white seine twine connecting the one end of the twine to the twisted pool noodle and the opposite end of one of the pool noodle to the middle of one of the chromanoodles. Students should separate the tow rope into two circles to make two identical cells. They should add another twisted pool noodle to each cell so that each cell has two twisted pool noodles. Next, they should add white seine twine connecting one end of the twine to the twisted pool noodle and one end to the middle of the chromonoodle. They should move the chromonoodle toward the twisted pool noodles. Then they should recreate the nuclear membrane with the yellow seine twine (one piece for each cell). Finally, they should remove the twisted pool noodle and the white seine twine and replace the chromonoodles with the piles of colored yarn.
Part Two: Fertilization
In this portion of the activity, student will use what they learned about meiosis and fertilization to create model that shows how a zygote is formed. Students should refer to Fertilization if they have questions.
First, students should make one haploid egg cell and one haploid sperm cell. Next, they should fuse the egg and sperm cell membranes to touching them. Students should move the nuclear membrane of the sperm cell into the egg and “unpack” the genetic material by replacing the yarn with chromonoodles. They should place two twisted pool noodles at either pole of the egg cell. They should move the egg and sperm nuclei closer together until they touch and remove the nuclear membrane. Finally, they should attached yellow seine twine to each of the chromonoodles and the twisted pool noodles. All chromonoodles should be lined up along the middle of the newly formed zygote. (Note: Here are two examples of student work.)
Part Three: Karyotyping the Embryo
After watching the karyotyping video, students will create a karyotype for their embryo by matching homologous pairs of chromonoodles and placing them on a karyotype form to determine total number of chromosomes and the gender of the embryo.
Part Four: Abnormal Chromosome Arrangements
Using the student handout, students should pick one of the abnormal karyotypes. They should design a model using the chromonoodles that would explain how that sex cell was formed. They should make a sketch of the model in their lab notebooks labeling the important structures.
Bring the class back together and using the chromonoodles relate what is happens in meiosis to the Punnett square model. Demonstrate to students the probability of certain types of gametes based on the models they developed in part four of the activity.
Using the examples of spermatogenesis and oogenesis, explain to students the slight model variations in nature. (Note: I use the following images (Gametogenesis and fertilization, Oogenesis, and Spermatogenesis) to help my students fully understand the process they just modeled. Students place these images in their lab notebook and write a short summary for each.)
Student pairs will share their stop-motion videos that they created yesterday. Each student group will introduce their video and debut it.
Guidelines for this assignment are here. (Note: In the case of large classes, this may require an entire class period. Therefore, it would need to occur on a separate day.)