MITOTIC PHASE ALTERNATES WITH INTERPHASE IN THE CELL CYCLEChapter 12 section 2

TERMS TO KNOW

Chromatid- Each of a pair of identical DNA molecules after DNA replication, joined at the centromere.

Chromatin- Protein/DNA complex making the chromosome.

Chromosomes- Molecules of DNA complex with specific proteins responsible in eukaryotes for storage and transmission of genetic information.

Kinetochore- Structure forming at centromere during Mitosis for binding microtubules.

THE CELL CYCLE

PHASES OF THE CELL CYCLE

The mitotic (M) phase of the cell cycle alternates with the much longer interphase.

The M phase includes mitosis and cytokinesis. Interphase accounts for 90% of the cell cycle. During interphase, the cell grows by producing

proteins and cytoplasmic organelles, copies its chromosomes, and prepares for cell division.

INTERPHASE!!!

Interphase has three subphases: the G1 phase (“first gap”), the S phase (“synthesis”), and the G2 phase (“second gap”).

During all three subphases, the cell grows by producing proteins and cytoplasmic organelles

However, chromosomes are duplicated only during the S phase.

MITOSIS

Produces two identical daughter cells Has 5 different stages: Prophase,

prometaphase, metaphase, anaphase, and telophase.

Cytokinesis is somewhat a part of mitosis, but differs depending on the type of cell

- begins immediately following telophase

BREAKDOWN OF MITOSIS

PROPHASE

In prophase, the chromosomes are tightly coiled, with sister chromatids joined together.

The nucleoli disappear. The mitotic spindle begins to form. It is composed of centrosomes and the

microtubules that extend from them. The centrosomes move away from each other,

apparently propelled by lengthening microtubules.

PROMETAPHASE AND METAPHASE

Nuclear membrane dissipates Proteins attach to the centrosomes, creating the

kinetochores. Microtubules attach to kinetochores Chromosomes begin moving and the spindle

fibers align them in the middle.

ANAPHASE

The chromosomes separate at the kinetochores. They move to opposites side of the cell. Typically the shortest phase of mitosis

TELOPHASE

Chromatids are at the opposite sides. New membranes form around the daughter

nuclei. Chromosomes disperse and spindle fibers

disperse. Cytokinesis will start to begin.

CYTOKINESIS

Animal cells: forms a cleavage furrow, which pinches the cell in two. This is caused by a fiber ring composed of a protein called actin around the center of the cell contracts.

Plant cells: a cell plate is synthesized between the two cells, which is produced by vesicles that are from the Golgi apparatus.

ANIMATION

http://www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/MitosisFlash.html

THE MITOTIC SPINDLE

The major driving force in mitosis. It is fibers composed of microtubules and

associated proteins. The spindle assembles during prophase Assembly of the spindle microtubules starts in

the centrosome, which organizes the cell’s microtubules.

BINARY FISSION

Prokaryotes reproduce by binary fission. In binary fission, chromosome replication begins

at one point in the circular chromosome, the origin of replication site, producing two origins.

As the chromosome continues to replicate, one origin moves toward each end of the cell.

While the chromosome is replicating, the cell elongates.

When replication is complete, its plasma membrane grows inward to divide the parent cell into two daughter cells, each with a complete genome.

THE EVOLUTION OF MITOSIS (BINARY FISSION?!?!?) Scientists believe that mitosis had its origins in

binary fission. Some of the proteins involved are in both binary

fission and mitosis, which two of them are related to actin and tubulin.

As eukaryotes evolved, the process of binary fission gave rise to mitosis.

VIDEO TIME

http://www.youtube.com/watch?v=VlN7K1-9QB0 http://www.youtube.com/watch?v=hOyUcjqcGp

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