My-tosis or Your-tosis??

Today in class, we talked about the cell cycle, and, more specifically, cell division. The cell cycle itself is the entire process through which the cell prepares for division and then actually divides. The entire process of preparation and division takes a long time in adults - anywhere from 18 to 24 hours!

The cell does a lot in preparation for division - it has to duplicate its genetic material (DNA) in order to ensure that its daughter cells are identical to the original cell, and grow to accomodate its expanding contents. This part of the cell cycle, known as interphase, is so important that it occupies the vast majority of the cell cycle. Out of roughly 22 hours, 21 are dedicated to preparing for cell division!

The remaining hour-ish is occupied by cell division, known to us science folk as mitosis. There are four major phases of mitosis through which a cell divides:

Prophase

Metaphase















Anaphase



















Telophase











Once the cell completes telophase, it is ready to split in two. This is the final stage of the cell cycle, also known as cytokinesis.

This type of cell division occurs in your non-reproductive body cells in order to allow you to grow (the bigger you get, the more cells you contain), develop and repair injuries that you sustain. Cell division is very important!

In an adult, it may seem as though cell division occurs rather slowly....compared to an embryo, it is slow! Remember, adult cells proceed through the cell cycle within 18-24 hours. Embryonic cells, however, divide every 30 minutes! That means that within a half an hour of your conception, you became two whole cells. An hour after you were conceived, you were nothing but 4 cells; after 90 minutes you were 8 cells; within 2 hours you were 16; then 32, then 64; then 128, and so on and so on, until you were born as a multicellular baby with specialized cells! All of that has to happen very quickly!

To revisit the interactive mitosis tutorial, visit the following website:
http://www.sci.sdsu.edu/multimedia/mitosis/

This week, we will also learn about how a different type of cell division, called meiosis, produces reproductive cells (sperm and egg cells) and how it compares to mitotic cell division.

This week's key terms:

• cell cycle
• interphase
• mitosis
• cytokinesis
• asexual reproduction
• binary fission
• regeneration
• gamete
• egg
• sperm
• fertilization
• meiosis

Have a great week! Sorry, but I have to split! : P