Student Goals

• Explain the purpose of cell division

• Identify the steps and events of each cell phase.

Which nucleus is bigger?

Cell Size

• Cell size is constrained by cellular needs for raw materials and the chemical properties of molecules.– too big = can’t get enough

matter and energy or get rid of chemical wastes

– too big = too many demands on DNA – things get out of control

• Sometimes, smaller is better

They are exactly the same size.

Life of a Cell

• Cells lining the esophagus live for 2-3 days

• Cells lining the small intestine live 1-2 days

• White blood cells may live for only 10 hrs, or for decades

• Red blood cells live less than 120 days

• Muscle cells live for years• Nerve cells live for many

years

Cell Life

• Most of the time that a cell is alive, it is busy growing, making molecules and using them.

• This is called Interphase (the time between mitotic divisions)

• The DNA is strung out in the nucleus, invisible. (chromatin)

• When the cell reaches its size limit, it gets ready to divide in two in a process called mitosis.

• Before that can happen, the DNA and all the cellular organelles are replicated during interphase.

Life Cycle of a Cell

• Interphase – growth, increase in size, and synthesis of organelles and molecules – G1

– S

– G2

• Mitosis - Cell division– Prophase

– Metaphase

– Anaphase

– Telophase

– Cytokinesis

The Big Picture

• One cell becomes twoEach with the same number of chromosomes as the Parent cell

The Big Picture- 2

• Before PROPHASE the chromatin is replicated (copied).

• During PROPHASE it condenses into chromosomes.

• Each chromosome has a replicated twin = sister chromatids.

• These are the 46 chromosomes in a human cell as mitosis begins.

Chromatin > Chromosome > Chromatids

• Chromatin, Chromosomes, and Chromatids are all the same– named differently depending on the stage.

Chromatin

Chromosome

Chromatids

Differences between Chromatin/Chromosomes/Chromatidshttp://www.youtube.com/watch?v=s9HPNwXd9fk

1. Prophase Pro = pre (before)

2. Metaphase Meta = middle

3. Anaphase Ana = apart

4. Telophase Telo = two

5. Cytokinesis Cyto = cell, kine = move

Mitosis: What does it look like?

Identify each stage from the pictures

Mitosis: What does it look like?

Examine Allium root tips under the

microscope and identify the parts.

Mitosis: What does it look like?

Mitosis: What does it look like?

Quiz yourself

• Check out this website! (biologycorner.com) For a REVIEW and practice quiz!– http://www.biologycorner.com/bio1/

cellcycle.html

• Practice Quiz on Discovery Education– http://school.discoveryeducation.com/quizzes6/muskopf/

mitosis1.html