Cell Cycle and Cell Division

The Cell Cycle – is the series of events that take place in the cell from one cell division to another.

Cell Cycle

includes:

1-Interphase

2-Mitosis

3-Cytokinesis

Phases of the Cell Cycle – page 1601)Interphase – cell grows and organelles duplicate, Dna is copied and the chromosomes duplicate in CHROMATIDS, cell grows more and prepares for cell division. The cells that will not divide anymore are always in Interphase.

2)Mitosis – when the nucleus divide 3)Cytokinesis – when the organelles and the cytoplasm divides creating 2 identical cells – it is different in plant and animal cells

**What is Mitosis?????

Mitosis is the process in which the nucleus of a cell divides to generate two identical nuclei.

****Mitosis and Trait Diversity

• Identical nucleus have exact copies of the DNA, so the cells will be identical,too.

•Mitosis does not contribute to trait diversity in the population

Cell Division: Examples

Lizard - regeneration of the leg

Starfish - regeneration

Salamander - regenration

Regeneration in humans

Flatworms - regeneration

Plant Growth

All these examples are a result of Cell DivisionOther examples:

dead skin replacement

human growth

reproduction of unicellular organisms - as shown below

**Why is cell division important?

• Replacement of dead cells• Regeneration of body parts

• Growth of organisms

• Reproduction of unicellular organisms

Phases of Mitosis

Document school website, page 162 - don’t forget to read the additions we made during class

Centriole is an organelle composed of protein They appear, in pairs, close to the nucleus during cell division. The spindle fibers will form between the two centrioles and are attached to the centromere of a duplicated chromosome.

Spindle Fibers will pull the chromatids apart during cell division

Centrioles are present only in animal cells and some unicellular plant cells

Plant mitosis takes place with protein microtubules forming spindle fibers but without the help of centrioles.

Phases of Mitosis

Document school website, page 162 - read and check the additions we did during class.Prophase MetaphaseAnaphaseTelophase – end of Mitosis Cytokinesis – Plant and Animal cell

CYTOKINESIS

Contractile ring pinches the membrane and the cell divides in the pinched area

A new membrane forms inside the cell

What cells go through Cell Division?

Multicellular Organisms have two types of cells that divide:

a) Somatic Cells – ( soma = body in Greek)

are all the cells in our bodies

They will go through Mitosis and make our body grow, replace our skin, etc.

What cells go through Cell Division?

Second type of cell:

b) Sex Cells or gametes: two types – egg (females) and the sperm (males). Participate in sexual reproduction, generating new organisms

•The sex cells are formed through Meiosis – a different type of cell division and, they will not go through Mitosis

Page 163 - The results of Mitosis and Cell Division

*At the end of Mitosis, there are 2 nucleus with 46 chromosomes - 23 pairs of homologous*At the end of Cell Division - 2 identical cells with 46 chromosomes -23 pairs of homologous (each one of the new nucleus go to one of the new cells)

Types of Asexual Reproduction – organisms come from one parent

•Read page 164 and underline:1) the 2 different types of reproduction2) the 2 types of Asexual Reproduction and how they

happen3) underline the process of regeneration

Types of Asexual Reproduction – organisms come from one parent

•Budding - Ex: yeasts. Two new organisms are made from one single parent. The new organisms are identical to the parent cell.•Binary Fission – reproduction in unicellular prokaryotic

organisms - Two new organisms are made from one single parent. The new organisms are identical to the parent cell.•Regeneration of dead cells, body parts for certain organisms,

and also organs such as liver in humans.

Binary Fission in Bacteria

Budding in Yeast – page 164

Budding in Hydra – fresh water animals , few millimeters long

Regeneration – type of asexual reproduction –

Mitosis anaphase end of cytokinesis interphase

metaphase prophase telophase