Module 5
1. Module 5
1.24. Page 4
Module 5—Cell Division: The Processes of Mitosis and Meiosis
Reflect and Connect
Cell division and chromosome separation does not always follow the normal pattern. Nondisjunction events can lead to too many or too few chromosomes in gamete cells. After the process of fertilization involving a gamete with trisomy or monosomy, the resulting zygote will have too many or too few chromosomes, and each daughter cell from that zygote will also carry that error since mitosis will faithfully repeat the chromosome count in all of the body’s somatic cells. This can lead to individuals with serious genetic conditions. Currently, science allows tests to be conducted to analyze the chromosome count of an unborn fetus, but there are no genetic treatments to reverse the problem of nondisjunction.
The knowledge of how cells divide both mitotically and meiotically, and of what can go wrong in the process, has led scientists into many fields of research and technology. For example, stem cell research involves the study of cells that have not yet differentiated or specialized in cell division. Based on the understanding of cell division, scientists are developing ways to apply stem cells in the treatment of diseases where cells no longer perform their normal function.
Discuss
Stem cell research holds much promise for finding new treatments to many serious diseases. By starting with young, undifferentiated cells, scientists may be able to generate any number of missing or malfunctioning cells in adults. However, the collection of these cells destroys the blastocyst from which they are taken. From your reading of the text on page 527, and from your review of the video on Canada’s guidelines for stem cell research, take a position on whether or not Canada’s guidelines give enough freedom to scientists while still respecting ethical concerns. Discuss your position with your classmates.
Reflect on the Big Picture
Proper chromosome separation is the foundation of an organism’s life cycle. If the correct number and assortment of chromosomes are not present in a gamete when it is fertilized, the resulting error will be repeated throughout the entire organism when the fetus grows and develops by way of mitosis.
Unspecialized cells found in a blastocyst have not yet entered a defined cell line or cycle. As a result, they can be used to replace any damaged or ending cell lines in full grown adults. This kind of research can extend life and increase the quality of life for many people, but it must be ethically guided by careful debate on the societal level. Did you learn anything new or do you have a different perspective now that you have completed the lesson assignments and participated in the discussions? Develop a reflective paragraph that summarizes your perspective on stem cell research and submit it for feedback.
Module 5: Lesson 5 Assignment
Submit your completed Module 5: Lesson 5 Assignment to your teacher for assessment.