Week 7: Cell Division

By Richard McIntosh  (University of Colorado Boulder)

Discussion Question

Do you see advantages for a cell in having its spindle form inside the nucleus, rather than in the cytoplasm?  How about having the spindle in the cytoplasm and the chromosomes in the nucleus?

Separating Duplicated Chromosomes

Length: 29:34 minDownload: This Video
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Understanding Mitosis through Experimentation

Length: 39:02 minDownload: This Video

Moving Chromosome to the Spindle Poles

Length: 41:27 minDownload: This Video

Course Materials

Assignment and Quiz Questions and Answers (Educators Only)

Lecture Overview

The goal of these three talks is to define the problems that a cell faces as it prepares for division and to describe some of the ways it solves them. In Part 1, both the length and amount of DNA are presented as problems for chromosome segregation, particularly in eukaryotic cells. The actions of cohesins and of chromosome condensation are described as solutions. The mitotic machinery is introduced, including its diversity of form across phylogeny, however, the features that appear to be conserved are emphasized. This lecture may be useful for upper level undergraduate and graduate courses discussing mitosis and cell division.

The second lecture describes some key experiments showing the dynamics of a formed mitotic spindle and the ways these may contribute to accurate chromosome motion. Experiments that reveal aspects of the processes by which chromosomes attach to the spindle are presented. Mitotic motors are introduced and discussed in the light of what they probably do and do not accomplish to effect chromosome motion, including acting to improve the accuracy of chromosome segregation.

The third lecture presents evidence, largely from McIntosh’s lab, that shows how microtubule depolymerization can move chromosomes in vitro and explores the nature of some of the protein complexes that can couple chromosomes to microtubules and take advantage of this reaction.

Speaker Bio

Richard McIntosh is currently a Distinguished Professor Emeritus at the University of Colorado Boulder. He earned his bachelor’s and doctorate degrees from Harvard University in Physics and Biophysics, respectively. He taught cell biology at that institution briefly, then moved to the University of Colorado at Boulder, where he has worked ever since. His principal scientific interest is the mitotic spindle, i.e., the cellular machinery that segregates duplicated chromosomes in preparation for cell division. McIntosh’s lab has answered a number of questions on spindle structure and function using electron microscopy based 3-D tomography.

McIntosh has served as President of the American Society for Cell Biology and has been appointed an American Cancer Society Research Professor. He is a member of the American Academy of Arts and Sciences and the National Academy of Sciences. McIntosh is also a passionate advocate for biology research in Africa. He has spent a sabbatical year in Uganda, and directed courses in Tanzania and in Ghana.

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