Genes and Cell Division: Mitosis Chapter 5 Lesson 5A part 2

Objectives: I will be able to name and describe the four phases of mitosis in order.

The Cell Cycle There are two main phases in the cell cycle—interphase and the mitotic phase.

Interphase Interphase is the period during the cell cycle of a cell’s growth and development Most of the cells life is in interphase. During interphase, most cells go through 3 stages: Rapid growth and replication, or copying of the membrane-bound structures called organelles. Copying of DNA, the genetic information in a cell Preparation for cell division

Interphase – G1 phase Cells increase in size in Gap 1, produce RNA and synthesize protein. An important cell cycle control mechanism activated during this period (G1 Checkpoint) ensures that everything is ready for DNA synthesis.

Interphase – S phase The complete DNA instructions in the cell must be duplicated. DNA replication occurs during this S (synthesis) phase.

Interphase – S phase The cell’s DNA is copied during the S stage and is arranged as pairs of identical chromosomes called sister chromatids. This process is called replication.

Interphase – G2 phase During the gap between DNA synthesis and mitosis, the cell will continue to grow and produce new proteins. At the end of this gap is another control checkpoint (G2 Checkpoint) to determine if the cell can now proceed to enter M (mitosis) and divide.

Mitotic phase– Mitosis or M phase Mitosis or M Phase: Cell growth and protein production stop at this stage in the cell cycle. All of the cell's energy is focused on the complex and orderly division into two similar daughter cells. Mitosis is much shorter than interphase, lasting perhaps only one to two hours. As in both G1 and G2, there is a Checkpoint in the middle of mitosis (Metaphase Checkpoint) that ensures the cell is ready to complete cell division.

Mitosis the equal distribution of the parent cell’s genes between the 2 new daughter cells.

Mitosis During mitosis, the contents of the nucleus divide, forming two identical nuclei.

Mitosis Prophase Metaphase Anaphase Telophase Like interphase, mitosis is a continuous process that scientists divide into different phases: Prophase Metaphase Anaphase Telophase

Prophase first phase of mitosis nuclear membrane disappears Copied chromatin coils together condensing into chromosomes the sister chromatids are still attached by a centromere nucleolus disappears spindle fibers form

Prophase

Prophase

Metaphase all sister chromatids line up single file at the middle of the cell (the center of the spindle) the period of time when the centromere are on the equatorial plane

Metaphase

Metaphase

Anaphase each pair of sister chromatids separates into 2 chromosomes called daughter chromosomes(separated sister chromatids) Spindle fibers begin to shorten, pulling the daughter chromosomes toward opposite sides of the cell (poles)

Anaphase

Anaphase

Telophase it begins when the daughter chromosomes reach the end of the spindle Nuclear membrane forms around the chromatin daughter chromosomes begin to uncoil nucleoli reappear Spindle fibers break down Two identical nuclei form

Telophase

Telophase

The 2 cells which result from mitotic division followed by cytokinesis are called daughter cells. Daughter cells are actually cells entering interphase. Daughter cells have exactly the same genes as the mother cell. The purpose of mitotic cell division is to insure that each new daughter cell has genes identical to those in the parent cell.

The Mitotic Phase

The Mitotic Phase

The Mitotic Phase

The Mitotic Phase

Cytokinesis In cytokinesis, the cytoplasm divides and forms two new daughter cells.

cytokinesis The division of the parent cell’s cytoplasm after mitosis is finished. Provides each daughter cell with cytoplasm and organelles.

takes longer in an animal cell than a plant cell Cell division varies in different types of cells. Some differences between plant and animal cell division are: takes longer in an animal cell than a plant cell plant cells don’t have centrioles cytokinesis is different in plant cells – forms a division plate rather than pinching in.

Results of Cell Division The cell cycle is important for reproduction in some organisms, growth in multicellular organisms, replacement of worn out or damaged cells, and repair of damaged tissues. In some unicellular organisms, cell division is a form of reproduction. Cell division allows multicellular organisms to grow and develop from one cell.