Cell DivisionChapter 10

Anatomy of a Chromosome

Centromere- where the two chromatids attach

Chromatid- two exact copies of DNA that make up a chromosome

Limits to Cell Growth• DNA Overload

– The larger a cell becomes, the more demands the cell places on its DNA

• Exchanging Material– The cell has trouble moving enough nutrients

and wastes across the cell membrane if the cell is too big.

– Surface Area:Volume ratio can’t be too small

Cell Cycle• Interphase (inter- means “between”)

– G1 phase – Cell growth– S phase – DNA replication– G2 phase – preparation for cell division– Cells are in interphase most of the time.

• M phase– Mitosis: prophase, metaphase, anaphase,

telophase, cytokinesis

• G0 phase– Cells that cannot divide like nerve cells, red

blood cells, and cardiac cells

Prophase

• What are the important events happening during Prophase?

Pair of centrioles

Plant cells in prophase

A? B? C? D?

Prophase

• Chromosomes condense into sister chromatids

• Chromatids are joined by a centromere

• Centrioles appear and form mitotic spindle

• Nucleolus disappears and nuclear envelope dissolves

• Longest phase of mitosis (50-60%)

Pair of centrioles

Plant cells in prophase

Metaphase

• What events are occurring during Metaphase?

Animal cell

Plant cell

A? B? C? D?

Metaphase

• Centrioles on opposite ends of the cell

• Microtubules of mitotic spindle attach to the centromeres

• Chromosomes line up across the middle (equator) of the cell

Animal cell

Plant cell

Anaphase

• What important events are occurring at Anaphase?

Early anaphase (plant) Late anaphase (plant)

Anaphase (animal)A? B? C? D?

Anaphase

• Sister chromatids separate

• Chromosomes migrate to opposite ends of the cell

Early anaphase (plant) Late anaphase (plant)

Anaphase (animal)

Telophase

• What important events happen during Telophase?

Animal cell

Plant cell

A? B? C? D?

Telophase

• Chromosomes begin to disperse

• Nuclear envelopes reform

• Mitotic spindle breaks apart

Animal cell

Plant cell

Cytokinesis

• Difficult to distinguish from telophase• In animal cells the cell membrane pinches in

forming two daughter cells• In plant cells a cell plate forms between the

daughter nuclei and a new cell wall forms at the cell plate

Animal cell

Plant cell

Which stage is each photo in??

How do you know??

What are the important events at each phase?G1 phase –??S phase –??G2 phase –??

What types of cells would be inG0 phase??

Now its YOUR turn!

Cancer

• Uncontrolled cell growth– Caused by smoking, exposure to radiation or

certain chemicals, some viruses

• Cancer cells smother normal cells

• Treatment options– Surgery to remove tumor– Radiation therapy to halt cell division– Chemotherapy to halt cell division