Most nerve cells in the adult human central nervous system, as well as heart muscle cells, do not divide. In contrast, cells lining the inside of the small intestine divide frequently. Discuss this difference in terms of why damage to the nervous system and heart muscle cells (for example, that caused by a stroke or heart attack) is so dangerous. What do you think might happen to tissues such as the intestinal lining if a disorder blocked mitotic cell division in all cells of the body?

When considering the stages of the cell cycle, which stage is best associated with cells that do not divide, such as nerve cells? G1 phase M phase O None - all cells divide S phase G2 phase GO phase Pickles are often preserved in a 20-30% salt solution called brine. How does brine prevent contamination by microorganisms? Bacteria can't survive in hypotonic solutions because of the added pressure of the water they take in causing them to burst. O Bacteria can't survive in a hypertonic solution because they lose too much water and die. O The high salt concentration increases the pH of the environment, making it unfavorable for bacteria to live there. The high salt concentration creates an isotonic environment that the bacteria cannot live in. Bacteria cells are unable to digest the salt, thus killing the cells by starvation.

In a dividing cell, the duplicated sets of chromosomes move along microtubules to opposite ends of the cell. How would you use an inhibitor to show that microtubules are essential for chromosome separation?  What control treatment(s) would you use? What kind of cell junctions would you expect to find, and why, in a small animal where a chemical signal passes rapidly through cells to go from the head to the tail?

In the experiment below, you have treated cells with different cancer drugs, stained them with propidium iodide, and analyzed them by flow cytometry. Which of the following histograms illustrates what you would expect to see in the event that the spindle assembly checkpoint is activated (focus on the solid line, the dotted line is normal cell cycle control)?       1. D 2. C 3. A 4.B

One approach to studying the regulation of cell cycle progression (particularly in an era when genetic and molecular biology manipulations were less readily accomplished in mammalian cells) was to use treatments that induced cells to fuse and then monitor the behavior of the two nuclei in the resulting cell. The figure below depicts data from one such study.  The investigators did preliminary work to produce populations of cells that were synchronized in various stages of the cell cycle (G1, S, or G2 in the examples shown below). They then fused the cells in different combinations and monitored subsequent events in each of the nuclei. For purposes of this question, we will pay particular attention to what occurred in the nucleus that came from the cell in G1. In one experiment (I), cells in the G1 and S phases were fused.  That event caused the nucleus from the G1 cell to very quickly enter the S phase (sooner than it would otherwise have done so).  In contrast, in a second experiment…

Oncologists (cancer doctors) frequently measure the mitotic index of tumor cells when they are removed via surgery or biopsy.  What do you think is the value of finding out the mitotic index of these cells?

Can you draw 4th cell division of the adult stem cells. 1st and 2nd are symmetrically. 3rd and 4th are asymmetrically. What kind of cell is the product at the 4th division? Explain your reasoning