A Day in the Life of a White Blood Cell... The Cell Cycle! A Day in the Life of a White Blood Cell...

Their cells are the same size…the elephant just has more of them. Limits to Cell Growth Living things grow because they produce more cells, not because cells grow enormous (exception: fat cells and muscle cells can increase in size) On average, the cells of an adult are no bigger than those of a younger animal. We know living organisms are made up of cells. How are the cells of these 2 organisms different? Their cells are the same size…the elephant just has more of them.

Instead of growing larger, cells divide. Cell growth is limited by the surface area to volume ratio. Instead of growing larger, cells divide.

Mitosis Definition: A cell dividing into two cells that are identical to the original cell.

Rates of Cell Growth vary depending on the kind of cell. E Rates of Cell Growth vary depending on the kind of cell. E. coli can double every 20 - 30 minutes! Some cells rarely divide, and some cannot divide at all. Skin cells and the cells in your taste buds are constantly dividing to replace old cells.

In this drawing, what color is the DNA? DNA is the instruction manual of the cell.

DNA is sort of like the instruction manual for a cell phone: there are different chapters in the instruction manual for how to text, how to check voicemail, how to change ringtones, how to change your background… DNA also has different “chapters” that give the cell instructions for different things. These chapters are called genes.

DNA is very long, so it can twist up like a rope and be packaged into chromosomes.

Chromosomes – DNA strands condensed together in a cell’s nucleus

What would happen if cells divided without replicating or copying what’s inside…like their DNA? If we didn’t divide, after each division cells would have half the amount of DNA genetic information.

What if your chromosomes kept dividing without replicating? Your skin cells have 46 chromosomes. Your next set of skin cells would only have 23 chromosomes…like a bean! …and their next set of cells would have about 11 chromosomes…like a wallaby!

Mitosis Meiosis Mitosis is cell replication and division. Mitosis is how all our body cells divide except for reproductive cells. After mitosis, the new cells have the same number of chromosomes (46) as the original cell. Meiosis takes place in reproductive cells to produce gametes (sperm and egg). After meiosis, the new cells only have half the number of chromosomes (23) as the original cell.

Not mitosis but meiosis… The only type of cell that does not divide by mitosis before it divides is a gamete (sperm or egg cell)

The cell’s life cycle can be divided into phases. Interphase Mitosis Cytokinesis

After interphase come mitosis and cytokinesis… I. Interphase Mitosis – cell division P. Prophase M. Metaphase A. Anaphase T. Telophase Cytokinesis – cytoplasm division So all together, it’s I.P.M.A.T. and Cytokinesis

What order do these pictures go in?

Interphase: cell is working. Doing what it is that cells do Interphase: cell is working. Doing what it is that cells do. (Cell growth, DNA replication, & preparation for mitosis) Remember that DNA provides the instructions for the cell. During interphase the cell prepares for cell division by copying its DNA. This way both new cells will each have a set of instructions. (Which means the cells won’t turn into beans or be stuck on the same ringtone!)

This is an image of many stained onion root cells This is an image of many stained onion root cells. Can you see more than one nucleus in any of the cells?

Prophase First phase of mitosis. Replicated DNA is packaged into chromosomes. Nucleolus and nuclear membrane disappear.

Metaphase Shortest phase. Chromosomes line up across the equator or center of the cell Fibers attach to the chromosomes to prepare to pull them apart

Anaphase Chromosomes are pulled in half and pulled to opposite sides of the cell.

Telophase: Final stage of mitosis DNA uncoils into two separate nuclei A nuclear membrane forms around each set of DNA Now mitosis is complete but the cell cycle is not…

Cytokinesis Division of cytoplasm into the new cells. Cell membrane pinches into two parts to form two new cells, each with their own nucleus and organelles. In animal cells, the membrane pinches into a cleavage furrow. In plants, a cell plate forms between nuclei and forms the cell wall.

Interphase Prophase Metaphase Telophase Anaphase Cytokinesis

Fun with Mitosis!! http://www.dnatube.com/video/4328/The-Stages-of-Mitosis http://www.dnatube.com/video/2380/Interpretive-Mitosis

Not all cells go through the cell cycle at the same speed Not all cells go through the cell cycle at the same speed. Some cells rarely divide. Growth and division can be turned on and off when needed. Normal well behaved cells will grow in a culture dish until they come in contact then stop growing (repairing an injury, cut etc.)

How do our cells control the cell cycle? The cell cycle is regulated by cell regulator proteins called cyclins.

What happens if something goes wrong in the cell cycle? Different problems with the cell cycle can cause different types of CANCER. Uncontrolled Growth = lost ability to control rate of growth. (In culture dish cancer cells do not stop growing when they come in contact with another.)

Cells from the lining of your large intestine Cancerous (disorganized, big cells, too many cells) Normal (organized, small cells)

Chemotherapy is a type of cancer treatment that kills cells that divide quickly. This includes cancer cells, but it also includes your intestines, stomach lining, and hair follicles.

Identical twins