Cell Division:Cells do not increase in size. They increase in number.Chapter 8-2 & 8-3

Cell Cycle

Time from beginning of one cell division to the beginning of the next

Cell doubles its contents so it is ready to divide into two completely independent cells

3 steps:1. Interphase

2. Mitosis (M phase)

3. Cytokinesis

1. Interphase (G1, S, & G2 phase) G1 – cell grows in size,

organelles in cytoplasm are copied

S – DNA is copied G2 – cell prepares for

division Cells spend most of

their lifetime in interphase

2. Mitosis (M phase)

Division of the nucleus

Creates two identical diploid cells

PMAT

Mitosis – Prophase

Nuclear membrane disappears

DNA – shorter and thicker and forms a chromosome

Chromosomes double to sister chromatids

Centrioles move to opposite ends of a cell

Spindle fiber – cell skeleton begins to form

                                                                                

                            

Mitosis - Metaphase

Doubled chromosomes attach to spindle fibers by the centromeres

Chromosomes pushed and pulled by spindle fibers

Line up along the middle

Shortest stage

Mitosis - Anaphase

Sister chromatids separate at the center

Centromeres split apart Each sister chromatid is

pulled toward an opposite side of the cell

                                                        

Mitosis - Telophase

Chromatids reach opposite poles

Spindles break down Nuclear membrane

reappears There are now 2 separate

nuclei

3. Cytokinesis

Division of cytoplasm Cell membrane pinches

to form two new cells Animal cells –

cytoplasm & cell membrane pinches

Plant cells – cell plate forms and becomes the cell wall

Cell Cycle – Animal Cell

Cell Cycle – Plant Cell

Whitefish

Onion Root Tip

Cells do not increase in size. They increase in number.

Meiosis: reduces the chromosome number by half in new cells (gametes)

Meiosis

Creates four haploid cells (gametes)

Two nuclear divisions occur without DNA being copied in between

Meiosis

Interphase Meiosis I

Prophase I Metaphase I Anaphase I Telophase I & Cytokinesis (results in 2 diploid cells)

Goes directly into Meiosis II Prophase II Metaphase II Anaphase II Telophase II & Cytokinesis (results in 4 haploid cells)