The Cell Cycle

Mitosis and Interphase

Interphase

• The time between cell division

• Cell is doing its job• DNA duplicates-

chromosomes make exact copies of themselves

Genetic material is all strung out as chromatin

Nuclear membraneclearly in place

Mitosis

• Cell divides to form two new identical cells

• Can look at four different stages– Prophase– Metaphase– Anaphase– Telophase

Prophase

• DNA condenses to form distinct chromosomes

• Nuclear membrane disappears

What is a chromosome?

• the nucleus ...• ... is the control center ...• ... which has the genetic material ...• ... which is DNA

(deoxyribonucleic acid)• * lots of DNA when it is bunched up is called a

chromosome

Chromosome

CHROMOSOMES = LOTS OF DNA

• Chromosomes are only visible during cell division

Metaphase• Chromosomes line up

in the middle (equator) of the cell

• Spindle fibers attach

Anaphase

• Chromosomes separate and move toward the opposite ends of the cell (poles)

Telophase

• Chromosomes reach the poles

• New nuclear membrane forms

• Chromosomes unwind to become thread-like chromatin again

Cytokinesis

• The cytoplasm is evenly divided

• New cell membrane forms in animal cells

• New cell wall is built across for plant cells

What is the end result of mitosis?

OK, fine…but who really cares about MITOSIS and diving cells???

Nerve cells…

• …remain in INTERPHASE for long periods of time.

• They go through mitosis about once every 75 years.

• So?…

Damage to these cells…

• …is often very serious.

Some damage is not permanent

• Gloria Estefan was involved in a tragic tour bus accident.

• Surgeons were able to repair her nearly severed spinal chord.

• She recently donated $1,000,000 for spinal chord injury research---->

Cancer cells…

• …behave much differently than nerve cells.

• …spend very little time in interphase and go through mitosis uncontrollably.

• Approx. 1/10,000 of your cells are cancerous-the good news-your defense cells usually kill them fast-->