CELL DIVISION

Unit 3 Part 2 – The Cell

Cell Cycles

No nucleus No membrane bound

organelles (ex. mitochondria, vacuole, chloroplast) A.) Cell division takes

place in 2 steps: 1.) DNA is copied 2.) Cell splits by

binary fission

Contain a nucleus and organelles.

Have a cell cycle Repeating

sequence of growth and division

Prokaryotic Cells Eukaryotic Cells

Eukaryotic Cell Cycle

3 Stages: Interphase

G1 – Growth S – DNA Synthesis G2 – Growth

Mitosis – Division of Nucleus P – Prophase M – Metaphase A – Anaphase T – Telophase

Cytokinesis Division of cytoplasm

Terms to know for Mitosis

Chromatin The stringy, filamentous,

working form of DNA. ReplicatChromosome

One of the 2 copies of coiled DNA.

ed Chromosome The 2 identical copies of a

of DNA molecule attached by the centromere.

Sister Chromatid 1 individual strand of the

attached identical copies of DNA.

Non-Replicated Chromosome Single strand of DNA;

unattached and coiled.

Spindle Fibers Fibers that are

attached to centrioles to help pull apart chromosomes

Centrioles Organelles that aid

in pulling apart chromosomes

Centromere Structure that holds

the replicated chromosomes together

Sister Chromatids

Replicated Chromosome

Centromere

Non-Replicated Chromosome

Chromosome

Interphase

G1 – first growth phase: The cell doubles in size and

the organelles double. S – synthesis phase:

the DNA that makes up the chromatin is copied (DNA replication) this is the longest phase of interphase.

G2 – second growth phase: Growth and preparation for

mitosis.

This is when the cell functions as the type of cell it is and then prepares to divide.

The LONGEST phase of the cell cycle.

90% of the cell’s life is spent in Interphase.

The cell does not look unique. The nucleus and the nucleolus are visible;The nuclear membrane is intact and visible.

Interphase (G1, S, G2)

Mitosis (PMAT)

Mitosis: The nucleus of a cell

is divided into two nuclei with the same number of chromosomes (2n=diploid.)

Consists of 4 phasesProphaseMetaphaseAnaphaseTelophase

Prophase

Longest phase of Mitosis.

Chromatin coils and forms chromosomes.

Nuclear envelope breaks down.

Centrioles migrate toward opposite ends.

Spindle fibers form and attach to the centromeres.

Metaphase

Chromosomes line up in the middle of the cell.

Anaphase

Centromeres of each chromosome split.

Spindle fibers contract and separate the two sister chromatids pulling them to opposite poles.

Each chromatid becomes a separate (non-replicated) chromosome in each daughter cell.

Telophase

Last stage of Mitosis.

Spindle fibers break down.

Nuclear envelope reforms.

Chromosomes at each pole uncoil and become chromatin.

Cytokinesis

NOT part of mitosis.

The cytoplasm divides into two cells.

Cell membrane reforms.

In plant cells the cell wall reforms and the cell membrane is laid down.

Click the image to play the video segment.

Video 1

Animal Cell Mitosis