Cell Division—Mitosis Notes

Why do Cells Need to Divide?• Transport of materials in and out of

the cell is MUCH FASTER over short distances.

• DNA codes the proteins our cells need to survive. The larger the cell, the more protein it would need and DNA could not keep up!

• Surface Area to Volume Ratio – the larger the cell, the more volume it has. More is needed and more waste is produced. It would need more surface area than the membrane could provide.

Living things grow by producing more cells, NOT because each cell increases in size

Why do cells need to divide?

Cell Division — process by which a cell divides into 2 new cells

Remember from the cell theory that all cells come from preexisting cells, so genetic information has to be passed from one generation to the next.

Cell Reproduction

Genetic information is contained in DNA – deoxyribonucleic acid which is in the nucleus of a cell.

DNA exists in the nucleus as long, threadlike strands called chromatin.

When a cell is going to divide and produce more cells, the chromatin winds up into a double, coiled structure called a chromosome.

Cell Reproduction

Cell Reproduction

All cells of the body EXCEPT the sex cells are called somatic cells.

Blood cells, nerve cells, skin cells, etc.

New somatic cells are made when one parent cell divides into two identical daughter cells

Cell Division

The Cell Cycle: The process somatic cells go through in order to grow and reproduce

The cell cycle is divided into two main parts: Interphase Mitosis (M Phase)

Cell Division

Interphase– this is a time of growth and a time when DNA is replicated (a copy is made) inside the nucleus of the cell

Interphase

G1 Phase – G is for GROWTH! The cell is growing and making proteins

S Phase – S is for SYNTHESIS (making something). This is when the DNA is replicated and an identical set of chromosomes is made

G2 Phase – G is for GROWTH. The cell continues to grow and is getting ready for mitosis (division)Interphase

Mitosis is when the nucleus divides

The second part of the cell cycle is mitosis and cytokinesis.

Cytokinesis is when the entire cell divides

Mitosis

Mitosis is divided into 4 phases:

ProphaseMetaphaseAnaphaseTelephase

Mitosis

The chromatin coils up tightly, gets shorter and thicker, and can be seen in the nucleus.

The chromatin is lined up in a way that two sister chromatids are held together at a middle point called a centromere. Each sister is a duplicate of the other (this was done in S phase).

Prophase

The nuclear membrane disintegrates and a spindle starts to form.

Spindle – Microtubules that line up in a spindle form in the cell to help division

Prophase

http://www.ptbeach.com/site/default.aspx?PageType=3&ModuleInstanceID=444&ViewID=7b97f7ed-8e5e-4120-848f-a8b4987d588f&RenderLoc=0&FlexDataID=347&PageID=907

Chromatids line up in the MIDDLE.

They attach to the spindle at the centromere in the middle of the nucleus (equator)

Metaphasehttps://commons.wikimedia.org/wiki/File:Mitotic_Metaphase.svg

Chromatids are pulled apart by the spindle. Each chromatid is now its own chromosome

Anaphasehttp://www.proprofs.com/flashcards/story.php?title=pratical-1_1

The chromosomes reach opposite ends of the cell and start to unwind.

Spindle disappears Two new nuclear membranes form around each set of chromosomes to form two new nuclei

Telophase

Telophase

http://home.apu.edu/~jsimons/Bio101/genetics.htm

The cytoplasm divides during cytokinesis

Cytokinesis

http://www.celldynamics.org/celldynamics/research/cytokinesis/index.html

In plant cells, a cell plate forms between the two nuclei and grows out to the edges, dividing the cell in half.

In the plant cell, a new cell membrane will form around each cell and a cell wall forms around the outside.

Plant vs Animal

Interphase M Phase (Mitotic)

G1-Growth Prophase – Chromatin Condenses

S-Synthesis-DNA Replication

Metaphase – Chromatids line up in the middle

G2 - Growth Anaphase – Chromatids separateTelophase – New nuclear membranes

Identify the Following Stages of Mitosis!

What is the longest part of the cell cycle?

Interphase

In which part of interphase are the chromosomes replicated?

S Phase

During what part of interphase does the cell grow and prepare for mitosis?

G2

What is the division of the nucleus called?

Mitosis

What is the division of the entire cell called?

Cytokinesis

If you are observing a cell and notice that the chromosomes appear to be lined up in the middle of the nucleus, what stage of mitosis are you observing?

Metaphase

If it looks as though the cell you see through the microscope has two nuclei, what stage of mitosis are you observing?

Telophase

A cell plate is forming in one of the cells that you are observing. Which of the following type of cells could you be viewing?

a. Human skin cellsb. Root tip cellsc. A fly’s eyed. bristles of an earthworm

Root tip cells!

In which of the following circumstances would cells NOT divide by the process of mitosis?

a. Repairing a cutb. Adding cells for an infant to growc. Creating sex cellsd. Replacing old skin cells

Creating sex cells

How many times do chromosomes separate during the process of mitosis?

One

http://v7.k12.com/sample_lessons/activities/images/swfs/9-12/ObservingMitosis.swf