The Cell Cycle

I need a volunteer! Does anyone have a mirror? Take it out and let me call on you to come up to the class I want to see how my hair is …or do I?

After reading about mitosis for homework, you should be able to explain this sentence: In biology division is the same thing as multiplication.

Differentiation How does one cell become not just many cells, but specialized cells, such as heart cells, brain cells, ear cells, stomach cells, etc? This is due to differentiation. At the earliest stage of life, cells are unspecialized, but the DNA inside of them causes them to differentiate, which means they become specialized- each with a different function.

Mitosis We all started off as a tiny, single cell. That cell then underwent a process called mitosis (cell division)which then created another cell identical to it.

After fertilization occurs, mitosis begins

A baby slowly grows into an adult This is a result of cells dividing to make more cells.

Mitosis involves somatic cells Somatic Cells All body cells are somatic cells- these cells undergo mitosis and are diploid which means they have 46 chromosomes. Gamete Cells Sperm and egg cells are gamete cells- these cells undergo meiosis and are haploid which means they have 23 chromosomes.

Cell Cycle The cell cycle is the regular sequence of growth and division that cells undergo. The cell cycle has three parts: interphase mitosis cytokinesis

Chromosome Chromosomes, which contain DNA, are found inside the nucleus in the cell

Cells divide to make specialized cells, which make up tissue, which make up organs=organism

Interphase The first stage of the cell cycle It is the period before cell division During interphase three things happen: The cell grows to its mature size It makes a copy of its DNA and organelles It prepares for mitosis

The cell spends most of its time in interphase. Mitosis takes about an hour to complete. Some cells divide every 24 hours. Cells must wait for a chemical signal before moving on to each phase of the cycle.

Mitosis Mitosis consists of four phases, prophase, metaphase, anaphase, and telophase Mitosis is the process by which a cell’s nucleus divides to create a daughter cell that is genetically identical to the parent cell It occurs in somatic cells only We call the original cell the parent cell and we call the new cell a daughter cell

When do your cells undergo mitosis? When healing injured tissue During growth- zygote to adulthood Regular maintenance of the body For example, stomach cells are in a harsh, acidic environment so they do not live very long and are replaced every few days by new cells through mitosis.

Prophase The nuclear membrane begins to break down The chromatin in the nucleus begins to condense and coil, like fishing line around a ball (becoming chromosomes) Since DNA has replicated in interphase, each rod has doubled, each being an exact copy of the other Spindle fiber forms from the centrioles

Prophase

Metaphase The chromosomes line up across the center of the cell Each chromosome attaches to a spindle fiber at its centromere, which holds the chromatids together

Metaphase

Chromosomes move along the spindle fibers and line up at the equator of the cell

Anaphase The centromeres split The two chromatids separate Each chromatid moves along the spindle fiber to opposite ends of the cell The cell stretches out

Anaphase Chromosomes begin to pull apart and move to opposite ends of the cell

Telophase The chromosomes begin to stretch out and lose their rod like structure This occurs in two regions at the ends of the cell A new nuclear membrane forms around each chromosome

Telophase

A Summary of Mitosis

Cytokinesis The cell membrane pinches in around the middle of the cell, eventually splitting in two Each daughter cell ends up with the same number of identical chromosomes and about half of the organelles and cytoplasm

Cytokinesis Division of the cytoplasm and organelles

Cytokinesis

Plant cell cytokinesis A plant cell does not divide in the same way as the animal cell because its cell wall is too rigid to squeeze together the way the animal cell does Instead a cell plate forms in the middle of the cell (made of sticky carbohydrate) The cell plate gradually develops into a cell membrane, then a cell wall develops

Plant Cell Cytokinesis

Note Check 1.What are the three phases of the cell cycle? 2.What are the four phases, in order, of mitosis? 3.In which phase does DNA replicate? 4.In your own words what is mitosis? 5.Why are the daughter cells genetically identical to the parent cell in mitosis?

Cancer Any substance that is known to cause cancer is called a carcinogen Cancer can be caused by genetic factors, environmental factors, and /or a unhealthy diet Cancer occurs when a mutation occurs in the DNA The cell no longer follows the “check point rules” of the cell cycle

Cancer Cancer cells can be thought of as “bully” cells, they don’t play by the rules They divide uncontrollably, invading the space of other cells so that they no longer can survive A tumor results from a mass of cells Benign tumors are “good” because they are localized and are easy to remove Malignant tumors are “bad” as they are able to spread throughout the body and are more difficult to treat

What phase am I?

Metaphase!

Which phase am I? Anaphase!

How about me?

Which Phase am I ? Telophase!

And what phase am I in?

Cell Cycle Quiz 1.The three parts of the cell cycle, in order are: a.interphase, mitosis, cytokinesis b.Mitosis, interphase, cytokinesis c.Cytokinesis, interphase, mitosis d.None of the above

2. The process by which cells divide and make cells with identical chromosomes is called: a.Interphase b.Meiosis c.Mitosis d.centromere

3. What phase of mitosis am I in?

4. Sister chromatids (identical chromosomes) attach to________at their centromeres. a.Spindle fibers

5. The identical cell created as a result of mitosis is called a_______. a.Son cell b.Parent cell c.Lovely cell d.Daughter cell