MitosisThe Cell Cycle

How do cells make more cells?

The Cell CycleMitosis and cell division are necessary for cells to be replaced after they die.

In you body, 3 billion cells die every minute.(age, damage, lack of nutrients)

We also need the cell cycle to grow.

The Cell CycleThree reasons why cells replicate:

1. To replace old cellsa. Cells die all the time. They need to be replaced by cell division

2. To heal injuries (scrape, cut, broken bone, etc)3. The allow the organism to grow

a. You have gone from 1 cell to ~40 trillion cells. How? Cell division!

The Structure of a Chromosome

Cell Cycle

Video

Cell Cycle● Interphase● Mitosis

○ Prophase○ Metaphase○ Anaphase○ Telophase

● Cytokinesis

InterphaseHappens between cell divisions

Longest phase of the cycle

Three major things happen:

● The cell does its job● The cell grows● The cell makes a copy of its

DNA (DNA Replication)

By the end of Interphase, DNA begins to condense into visible chromosomes

InterphaseReplication

Before mitosis can start, all the DNA needs to be duplicated, a process called replication. This happens during Interphase

End of InterphaseAfter the chromosomes are replicated in Interphase they need to bunch up into tightly packed structures.

● Double-Stranded

Chromosomes

● Centromeres

● Sister-Chromatids

Cell Cycle● Interphase● Mitosis

○ Prophase○ Metaphase○ Anaphase○ Telophase

● Cytokinesis

MitosisMitosis is the process by which genetic material (DNA) is replicated and then

divided in two identical sets of chromosomes. The end result of Mitosis is two identical cells.

Phases of Mitosis

ProphaseMetaphaseAnaphaseTelophase

Mitosis - Prophase→ DNA condenses into visible, double-stranded chromosomes

→ spindle fibres form off of the centrioles

→ nuclear membrane breaks down

Mitosis - Metaphase● double-stranded

chromosomes are connected to the spindle fibers

● double-stranded chromosomes are aligned at the equator (middle) of the cell

Mitosis - Anaphase● The spindle fibers begin to

contract and shorten● Centromeres separate● The double-stranded

chromosomes are pulled apart and the strands move to opposite ends of the cell

Mitosis - Telophase● There is a complete set of

chromosomes at each end of the cell

● The spindle fibers break down

● 2 nuclear membranes begin to form around the chromosomes

● Chromosomes begin to uncoil

● Cleavage furrow forms and begins separating the cytoplasm

Cell Cycle● Interphase● Mitosis

○ Prophase○ Metaphase○ Anaphase○ Telophase

● Cytokinesis

End of Cell division animation

Plant Cells

Cell Plate

Animal Cells

Cytokinesis

Cell Cycle● Interphase● Mitosis

○ Prophase○ Metaphase○ Anaphase○ Telophase

● Cytokinesis

Video

Cell Cycle→ aging is the slowing down of the cell cycle

→ as cells die they aren’t replaced

→ skin wrinkles, bones lose their density, ability to fight off diseases reduces

Cell Cycle→ cancer happens when the cell cycle continues out of control

→ tumours or cells where there not suppose to be

→ genes connected to controlling the cell cycle (mutations)

→ environmental and genetic causes

Video 1 and Video 2

Exponential Division