Chapter 4 Section 1Cell Division and Mitosis

The Cell Cycle -“life cycle” of a cell- series of events that takes place from one cell division to the next- no set time for cycle- ranges from minutes to days- not only used to make an organism, but also to replace parts in an organism such as skin, bone, blood, etc.

Interphase -period of growth and development of most eukaryotic cells (cells with a nucleus)- some cells, such as nerve cells and some muscle cells are always in this phase

Mitosis -Process in which the nucleus divides to form 2 identical nuclei- 4 steps:

1. Prophase2. Metaphase3. Anaphase4. Telophase

Chromosome - structure in the nucleus that contains heredity material

Chromatid - duplicated chromosome coiled tightly into 2 thickened identical strands

Steps to Mitosis:

1. Prophase -pair of chromatids are fully visible- nucleolus and nuclear membrane disintegrate-centrioles move to opposite ends of cells- spindle fibers begin to spread across cell

2. Metaphase

*** Plant cells do not have centrioles.***

-pairs of chromatids line up along the center of the cell- the centromere (center of the chromatid) attach to the spindle fibers, one on each side

3. Anaphase -centromeres divide and spindle fibers shorten- chromatids move to opposite ends of the cells- separated chromatids now called chromosomes

4. Telophase -spindle fibers disappear- chromosomes uncoil- new nucleus forms- animal cells- cell splits down the middle- plants cells- cell plate forms

Results of Mitosis:

Remember:1. It is the division of the nucleus2. produces 2 new nuclei that are identical to

each other and the original cell

- every cell in your body, except sex cells, have 46 chromosomes (23 pairs)

- all of these cells have the same set of genetic material (skin, hair, blood, liver cells all have the same nucleus and the same 46 chromosomes

Asexual Reproduction

-a new organism is made from one organism (one parent)- offspring will have heredity material identical to parent (clone)

Fission -process bacteria uses to reproduce- bacteria contains no nucleus so it cannot divide by mitosis- copies the genetic material and then the cell splits

Budding -type of asexual reproduction- adult will create a bud, which once large enough will break away