Saturday, September 29, 2012

Science Saturday: Mitosis Edition

I saw this beautiful image via the tumblr website It's Okay to be Smart, and thought it would be cool to do a post explaining the concept of mitosis, or cell division.  We need our cells to divide for growth and development and also to replace old/dead cells (such as dry/dead skin cells that slough off), This image neatly organizes the time lapse of mitosis in a lovely spiral - but just imaging this happening all at once in hundreds or thousands of cells at the same time!!

In this image, the DNA is dyed red and the cell membrane is dyed blue. The cells used for this image are HeLa cells, a very common cancer cell used in biology research.  For a great book read, check out "The Immortal Life of Henrietta Lacks" by Rebecca Skloot to learn more about these cells and the influence it's discovery had on scientific research and on the sociopolitical struggles surrounding the Lacks family's life.
There are 4 main stages of mitosis: prophase, metaphase, anaphase, and telophase.  The process of mitosis is actually quite short, and cells spend most of their time in a stage called interphase, where the cell grows and is maintained through various "checkpoints" allowing DNA to replicate in preparation for cell division.

During prophase, the nucleus begins to disintegrate and DNA strands (which normally resembles a spaghetti-like structure called chromatin) coil up into X-shaped chromosomes.  Also, two structures called centrosomes form and leave a trail of microtubules as they migrate to opposite sides of the cell.  This microtubule "transport" system is how the chromosomes will separate. During metaphase, the chromosomes line up along the microtubules in the middle of the cell.  The centromeres start to "pull" the chromosomes apart toward each end of the cell in anaphase.  Once each "daughter" chromosome has reached their side of the cell, telophase begins, and the chromosome begins to uncoil back into it's original spaghetti-like state and the nucleus begins to surround it.  The cell membrane starts to pinch and furrow, beginning a process called cytokinesis, which will split the cell membrane resulting in two whole daughter cells that are exact genetic copies of the original parent cell.

What stages of mitosis can you spot in the photo above?

And for funsies, I remember watching this awful video in high school biology.  I think it's a perfect example of our love/hate relationship with the 90s :)  If you can handle watching the whole thing, I guarantee you will be "singing" it the rest of the day... 

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