Mitosis has to be one of the more beautiful things in nature. It’s a choreographed dance of the chromosomes. It’s so small that we can’t see it without a microscope, but it goes on in our bodies billions of times a day.
DNA is a very long molecule made up of the genetic alphabet (which has four letters: A, C, G, T). A gene is made of a certain sequence of DNA letters (or bases) and spells out an instruction for a step in the complex workings of our bodies (such as the structure of insulin). The genes are strung together along the chromosome, and each cell has a set of chromosomes. For our bodies to grow, these cells need to make copies of themselves. The problem of how to distribute the copied chromosomes evenly to the two “daughter cells” is handled very elegantly.
Mitosis is the solution. Mitosis is broken up into a series of phases: interphase, prophase, metaphase, anaphase, telophase. You could add prometaphase: the part of prophase between the nuclear membrane breaking down and metaphase (where the chromosomes line up at the metaphase plate).
Now follow the captions under the pictures.
At metaphase the chromosomes meet in the middle of the cell at the metaphase plate. Then as the cell divides to become two daughter cells, the two halves of the centromere split and travel along the microtubules in opposite directions, pulling the two halves of the chromosome behind them.
If a chemical that destroys the microtubules is added to a laboratory culture, the chromosomes are stopped at metaphase. Cytogeneticists (chromosome scientists) use this technique to get enough metaphase chromosomes for analysis. Chromosome banding helps recognise the chromosomes and identify any changes when an abnormality is suspected. Of course, the cell is also full of other organelles that have to be shared between the new cells.
The modelling clay images above are from my claymation showing mitosis. Modelling clay is a great medium for demonstrating and thinking about how things work, move and change. For the claymation I used a phone camera resting face down on a glass coffee table over the models.
Cross-posted to www.chromosomesandcancer.com.