cell division [cell reproduction] chapter 8-2. prokaryotes lack organelles simple celled organisms...

Cell Division[cell reproduction]

Chapter 8-2

•Prokaryotes

•Lack organelles

•Simple celled organisms

•Bacteria

•DNA- is circular, free floating

•Binary Fission- The division of prokaryotic cells into 2 offspring cells

•Eukaryotic Cells:

•more complex cells

•membrane bound organelles

•nucleus

•plant and animal cells

Cell Division in Eukaryotes

•Both the cytoplasm (fluid interior) and nucleus divide

•2 Kinds of Cell Division in eukaryotes

•1. Mitosis- results in identical genetic info. Regular body cells.

•2. Meiosis- reduces # of chromosomes by half. Only in sex cells.

•Repeating cycle of events in the life of a cell

The Cell Cycle

•The time between cell divisions is called- Interphase

•Most of cells life is spent in interphase

•3 stages of interphase

•1. G1 Phase

•2. S Phase

•3. G2 Phase

•G1 Phase: Offspring grow to mature size

•S Phase: DNA is copied (synthesized)

•G2 Phase: More growth and prepare for cell division

Interphase

Mitosis•Division of the nucleus- of all cells

but sex cells

•Occurs during cell division

•Divided into 4 phases (PMAT)

•1. Prophase

•2. Metaphase

•3. Anaphase

•4. Telophase

Prophase

•Chromosomes are condensed

•Each chromatid stays attached by centromere

•Nucleus and nuclear envelope break up

•Spindle fibers form (divide the chromatids)

Metaphase

•Chromosomes are easy to identify

• They line up in the center of the cell

•Spindle fibers attach to each chromosome

Anaphase

•Chromatids separate from its pair

•Spindle fibers start to break down

•Cell becomes elongated

Telophase

•Chromosomes reach each end

•Spindle fibers disappear

•Chromosomes return to less tightly coiled state (chromatin)

•Nuclear envelope and nucleolus forms

•Last phase in Mitosis

Cytokinesis

•At end of telophase the cytoplasm begins to pinch and divide in a process known as cytokinesis.

•In animal cells a cleavage furrow separates the 2 new cells

•In plant cells, a cell plate forms in between the 2 new cells.

Control over Cell Division

•Proteins regulate the process of cell division, these are coded for genes

•There are checkpoints along the way through Interphase to ensure there are no errors.

•If there is a mutation in a gene, than that protein may not work correctly

•Cell growth and division may be disrupted as a result of a mutation.

•This could lead to a tumor- clump of cells when a cell divides uncontrollably

•Your body’s checks and balance systems can not control the cell growth due to a mutation.

•The tumor could lead to cancer- a disease characterized by uncontrolled cell growth

•What can cause cancer?

•Defect in gene that regulates the cell cycle

•Mutation in gene

•Environmental risks- radiation, sun, diet