3.07 The Cell Cycle

Oh, quick, stop the movie! There is Dr Q. He's pulling up beside us in his Jeep; he must be heading back to town for some supplies. He is revving his engine like he wants to race. If he wants a race, then a race he will get!

This bus might do 0 to 60 in 2 minutes, but we know that the tortoise always beats the hare. OK Q, it's a straight shot to the Lot's-O-Palms Oasis. The last one to the tourist info building eats a handful of rotten dates. Let's go!

In this race there are two basic portions. The first is a straight shot down the main road to the oasis which is the longest part of the race. The second part is a quick spin around the oasis which leads to the finish point.

As you'll see in this quick tutorial, cells live in basically one of two phases or stages for their entire lives. Open the Cell Cycle Tutorial and look and listen carefully!

So, just like the race we're locked in, the cell cycle has two main sections.

Interphase - composed of the G1, S and G2 phases described in the chart below
Mitosis - the process where the nucleus of the cell divides to form two nuclei. Each nuclei contains a complete set of the cells chromosomes.

The Stages of Interphase
G1 Phase	S Phase	G2 Phase
Cell growth-this would be the time from birth to adulthood if you were going to compare it to human lifespan. Work-The cell will perform a specific job thanks to the body's career counselor known as DNA. Cells in this stage will work and grow until it gets too large to continue normal daily activity. Cells will have to decide to "divide" or "die" at this point.	Cells will make a copy of its DNA (DNA Replication).	"Nesting" phase-cell gathers energy to get ready for the big event called "mitosis." Repair mistakes-At this point, if any mistakes in the DNA replication have occurred, the cell will either repair it or will terminate!

Whoa! What is going on with Q's Jeep? He is going the wrong way. Looks like old Dr. Q doesn't know the way to the Oasis very well. He'll be way off track if he doesn't get back on the main road at that next crossroad!

Sad to say, sometimes cell division gets off track! Cancer is a disease caused by cells that have gotten stuck in a rapid, uncontrolled cellular division phase. The DNA in cancer cells has been mutated and is no longer regulating normal growth and division in the cell. Mutations are changes in DNA (or RNA). Because of their rapid growth and division, these cells require lots more food than normal cells do; they often deprive healthy cells from getting the supplies they need to survive. Often in cancer, a mutation in the DNA causes cells to get out of control developing into tumors or cells that outgrow all the other cells around them.

Factors which can cause cancer:

solar radiation exposure
certain types of viruses
inhaled pollutants including first-hand and second-hand smoke from tobacco products and air pollution
pesticides
family genetics

World Wide Web icon Living in the desert, near the equator, the sun is very strong. We know that we must protect our skin to reduce risks of developing one of the most deadly kinds of cancer -- skin cancer. We can do a lot to prevent getting skin cancer, but most folks don't have any idea what to do. Click on the Why Files link below and find out what can be done to protect yourself from skin cancer. Look for kinds, causes, and methods of prevention.

Why Files: Bad News on Skin Cancer

There are many kinds of cancer and most people today have been affected in some way by cancer. This disease is one of the top health problems today and affects our lives and economy in profound ways. Research into cures and treatment of cancer is a billion dollar industry.

Continue to the Travel Log tab to finish up this activity.