Boo-yah Biology!

The Cell CycleMolecular Biology

Sumner HS

Cell Reproduction/Division

The ability of organisms to reproduce their kind is the one characteristic that best distinguishes living things from nonliving.

The continuity of life is based on the reproduction of cells, or cell division.

Cell Division Importance

Multicellular organisms depend on cell division for

Development from a fertilized cell

Growth

Repair or replacement of “bad” cells

Big Growth

We start as one cell

We end up being made of trillions of cells

They don’t magically appear **Poof!**

The result of countless cycles of growth and division of cells.

Question to ponder...

What tasks does a cell need to do in order to divide?

Have a 2nd copy of DNA

Have enough cytoplasm and organelles for a second cell

The Cell Cycle

Cells go through predictable, controlled patterns of growth or development and division.

Called the cell cycle

The Cell Cycle

Cell 2

Big Picture

Interphase/

MitosisCell 1

Cell 1

Cell 2

Big Picture Cont’dInterph

ase/Mitosis

Cell 1

Cell 1

Cell 3

Interphase/

Mitosis

Cell 2

Cell 4

Cell Cycle Major Phases

Interphase = period of growth, DNA replication and protein synthesis

Mitosis = cell division

Interphase

Interphase can be divided into subphases

G1 phase

S phase

G2 phase

G1 Phase

Rapid growth

High metabolic activity

Making lots of proteins

S Phase

DNA is copied (replicated)

Cell has twice the number of normal chromosomes.

Cell keeps growing

G2 Phase

More proteins made

Mitochondria & other organelles replicate

Cell keeps growing

Summarize

In your own words, summarize each of the phases of interphase.

Mitotic Phase

The Mitotic Phase has two major phases

Mitosis has four sub-phases

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

New Note Instructions

For each of the phases of cell division...

....don’t write down the details I put up

Instead, prepare to summarize the main events in about 10 words.

Prophase

Chromosomes coil up and become visible (twisted rubber band)

Centriole begins to form spindle, made from same material as cytoskeleton.

Nuclear envelope and nucleolus begin to disappear

Summarize!

Metaphase

Chromosomes move to “equator” of the cell

Each half of the chromosome is attached to a spindle fiber at the centromere.

Centromere is a protein that joins the two “sister” chromatids, or replicated chromosome pairs

Summarize!

Anaphase

Sister chromatids are pulled apart to opposite ends of the cell.

Each chromatid is now a separate chromosome.

Summarize!

Telophase

Genetically identical daughter nuclei form at opposite ends of the cell

Nuclear envelope begins to reappear.

Summarize!

Cytokinesis

In animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrow.

A “string” of cytoskeleton pinches the cell in two

Summarize!

Cytokinesis cont.

In plant cells, a cell plate forms between the cells after telophase.

Mitosis results in Mitosis results in

two identical cellstwo identical cells

called called daughter daughter cellscells

Mitosis results in Mitosis results in

two identical cellstwo identical cells

called called daughter daughter cellscells

Real Pictures: Early Prophase

Real Pictures: Late Prophase

Real Pictures: Metaphase

Real Pictures: Anaphase

Real Pictures: Early Telophase

Real Pictures: Late Telophase

Test Yourself

Identify prophase, metaphase, anaphase Identify prophase, metaphase, anaphase and telophase in these cells.and telophase in these cells.

Check Your KnowledgeCheck Your Knowledge