Cell Division (Mitosis) How does mitosis ensure that a new cell is identical to its parent cell?

The Cell Cycle● The regular sequence of growth and

constant division that cells undergo is known as the cell cycle.

● Three main stages: ◦ Interphase◦ Mitosis (4 Phases)◦ Cytokinesis

Stage 1: Interphase● During the first part of the cell cycle,

known as interphase, the cell grows to mature size, makes a copy of its DNA (Starts with 46 and ends with 92 Chromosomes), and prepares to divide into two similar cells.

● DNA is spread out (simplified) as chromatin

Stage 2: Mitosis

● Mitosis = The cell’s nucleus divides into 2 separate new nuclei, each with 46 chromosomes or 23 homologous pairs.

● One copy of DNA is distributed into 2 daughter cells.

Stage 2: Mitosis (Prophase)

● “Pro” means “first”: It is the first part of mitosis

● What happens?◦ DNA scrunches up into chromosomes also known as sister chromatids.

◦ Nucleus dissolves

Stage 2: Mitosis (Metaphase)

● Chromosomes line up in the MIDDLE of the cell

● Remember: Metaphase = Middle

Stage 2: Mitosis (Anaphase)

● Chromosomes are pulled to opposite ends of the cell by the centrioles with ropes called spindle fibers.

● Remember: Anaphase = Apart

Stage 2: Mitosis (Telophase)

● The cell starts to form two new nuclei around the chromosomes

● Chromosomes start to unwind back into chromatin

● Remember:◦ Telophase = Two Nuclei

Stage 3: Cytokinesis● Cytoplasm divides, distributing organelles into each of

the two new cells.● Each new daughter cell has the same number of

chromosomes as the original parent cell.● Remember:● Cytokinesis = Cytoplasm splits

Cytokinesis in Animal Cells● In animal cells the cell membrane

pinches in creating two new cells, (each with ½ the organelles.)

Cytokinesis in Plant Cells● Form a cell plate across middle that

eventually turns into a new cell membrane, (new cell wall follows.)

Lets see all of mitosis together:

https://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokinesis.html

Length of the Cell Cycle● Cells spend most of their time during the interphase

stage of the cell cycle.● Mitosis only happens at the end to make new cells

http://www.youtube.com/watch?v=m73i1Zk8EA0

Cell Cycle

includes

is divided into

http://www.youtube.com/watch?v=I5uFuvkN97I

Cell Cycle

includes

is divided into

http://www.youtube.com/watch?v=I5uFuvkN97I

Interphase Mitosis Cytokinesis

Prophase Metaphase Anaphase Telophase