Mitosis Flashcards
Describe the importance of cell culturing
Culturing cells in the laboratory, out of the body, is an important technique in biomedical and clinical research since it allows complete experimental control of the growth conditions. Much of our understanding of how cells grow and behave, as well as what goes wrong in cancer cells, has come from these sorts of experiments.
Describe vinblastine
The drug you will use is vinblastine, one of the vinca alkaloids originally derived from the periwinkle plant, a drug used as part of chemotherapy treatment of certain cancers. Because it inhibits cell division, it is potentially toxic to all cells. However, in chemotherapy, the dose is very carefully regulated so that it preferentially affects the most rapidly dividing cells, including tumour cells.
What are some of the errors that may be made in this practical
The cells will die if deprived of their growth medium. Don’t let them dry out as you transfer the coverslip from one container to the other. Also remember that there is a danger of contaminating the control medium in the Petri dish with inhibitor (or components of the staining solutions, see below).
What are the safety issues with this practical
Vinblastine is poisonous and must be handled with care. Take standard laboratory precautions (wear lab coats, do not eat or drink in the lab, keep the lab bench tidy, clean up spillages immediately) and handle the coverslips only with forceps. If you think you might have got any solutions on your fingers, wash your hands immediately.
Describe the cell staining method
Dry the forceps with tissue before picking up a cover slide with cells on and dipping in and out of the phosphate-buffered saline 5 times
Dip the cover slip in the acid-alcohol and hold for 5 seconds
Rinse by dipping in distilled water 5 times
Dry by placing cell side up on filter paper
Stain the cover slip with one drop in the centre before using surface tension to place on a slide
Describe prophase
Individual chromosomes within the nucleus begin to condense and take up stain. (In contrast interphase nuclei stain weakly, except for the nucleoli). DNA replication has already occurred so each chromosome consists of two chromatids attached at the centromere. The nuclear envelop breaks down.
Describe metaphase
Chromosomes are now maximally condensed. This is the only stage at which you might be able to visualise the X-shaped appearance of the joined sister chromatids. At the end of metaphase the chromosomes become lined up at the centre of the mitotic spindle, on the metaphase plate. When trying to identify metaphase, remember that the direction of the spindle doesn’t necessarily lie at right angles to the direction you are viewing the cel
Describe anaphase
The sister chromatids of each chromosome separate. Microtubules of the mitotic spindle attach to kinetochores on each side of the centromere, and pull one chromatid to each pole of the spindle.
Describe telophase
The two separated groups of chromosomes begin to form the nuclei of the two daughter cells. The chromosomes de-condense and the nuclear envelopes re-form. At the end of telophase cytokinesis occurs when the rest of the cell divides. In some cases you may be able to see evidence of the cleavage furrow where this is occurring.
