March 18, 2013

The Cell CycleA Story about Interphase,Mitosis,

and Cytokinesis

Asexual & Sexual Reproduction

Reproduction - The purpose of reproduction is to pass on genetic information from one generation to the next. This can take place via asexual or sexual reproduction.

Asexual Reproduction (Mitosis) - Results in offspring that are genetically identical to their single parent. In rare cases there may be genetic variability which might be caused by hormones in the organism.

Sexual Reproduction (Meiosis) - Results in offspring that are genetically variable. Offspring inherit half of their genetic information from each of the two parents.

Asexual Reproduction

Benefits

• Don't need to find a mate

• Don't need to perform specialized mating behaviours

• Don't have to possess specialized reproductive anatomy

Disadvantages

• No genetic variability (other than mutations)

Sexual ReproductionBenefits

• Genetic variation - not the same as a single parent but a combination or mixture of both

Disadvantages

• Must have specialized reproductive organs

• Must find mating partners

> Have to be able to perform specialized mating behaviours

• In plants, they often have to depend on insects for pollination

> they also have to be able to produce nectars for bees, flies, birds

• It is biologically costly

The Cell Cycle

• The entire life of a cell is called the cell cycle.

• The cycle can last 24 hours and has 2 main stages Interphase & Mitotic phase (mitosis).

• The cell spends most of its life in interphase.

Interphase

• Interphase is made up of 3 stages. They are known in short as G1, S, and G2.

• G1 known as Gap1 or Growth Stage 1 - The new cell begins to grow

• S known as the Synthesis Stage - The DNA replicates within the nucleus

• G2 known as Gap2 or Growth Stage 2 - The cell begins to prepare itself for cell division/replication (mitosis)

March 18, 2013

Interphase

Cellular division is needed for the survival of multicellular organisms.

There are 4 stages of mitosis that occur in the order of:

1. ___________

2. ___________

3. ___________

4. ___________

Mitosis- Cellular Division

1. 2.

3. 4.

\

Video Link

A trick to remember the order of the stages is I Put My Arm There, or PMAT

I= Interphase; the resting period of the cell between rounds of mitosis

P= Prophase - chromosomes prepare to divide

M= Metaphase - chromatids move to the middle

A= Anaphase- chromatids are far apart, at opposite ends of the cell

T= Telophase- Two different nuclei in 1 cell

Prophase• The first step of mitosis

• Cell prepares for division

• The chromatin is packed together to form chromosomes

• Centrioles begin to move to opposite ends of the cell

• Spindle fibres begin to form from the centrioles.

• The nuclear membrane starts to disintegrate

Prophase Metaphase• The second step of mitosis

• Chromosomes line up along the middle of the cell known as the metaphase plate with the help of the spindle fibres from the centrioles

• The nuclear membrane is not visible during this phase

March 18, 2013

MetaphaseAnaphase

• The third step of mitosis

• Identical halves of each chromosome are pulled towards opposite ends of the cell

• Identical halves of a chromosome are called sister chromatids.

• The nuclear membrane is not visible during this phase

AnaphaseTelophase

• The fourth and last step of mitosis

• The chromosomes are at opposite poles

• The nuclear membrane reforms around the chromosomes (common nuclear envelope)

• The cell begins to pinch inwards to start forming two separate daughter cells

Telophase Cytokinesis

• Occurs at the end of cell division.

• Divides the cytoplasm into two separate cells.

• The cell membrane pinches inward between the two nuclei and forms 2 daughter cells.

March 18, 2013

Paul Andersen - Bozman Science - The Cell Cycle Video

Test Your Knowledge

Use the graphics found in the box to the left to construct a cell in metaphase. When you are finished click on the center of the cell.

Test Your Knowledge

Correct! During metaphase, the chromosomes line up

along the cell's equator.Next

Test Your Knowledge

Use the graphics found in the box to the left to construct a cell in telophase. When you are finished click on the center of the cell.

Test Your Knowledge

Correct! During telophase, 2 nuclei share a common nuclear envelope

Next

Next

March 18, 2013