Chapter 9

Cell Division

Process of a cell dividing into 2+ daughter cells

Binary Fission

Prokaryotic cell division

Mitosis

Eukaryotic cell division that produces somatic cells

1 diploid → 2 diploids

Meiosis

Produces sex cells

Nucleosomes

Units of 8 histone proteins with DNA wrapped around them

Present as chromatin and chromosomes

Chromatin

Loosely packed nucleosomes in non-dividing cells

Chromosomes

Tightly packed nucleosomes in dividing cells

Cell cycle

G1 → S → G2 → Mitosis → Cytokinesis

Interphase

Non-dividing phase

G1 → S → G2

G1

Cell performs normal functions while growing and producing enzymes

S

Cell replicates DNA/centrosome producing replicated chromosomes with 2 sister chromatids

G2

Continues growth and produces proteins for M phase

Cell Cycle Regulation

Growth factors promote cell division

Cell cycle checkpoints regulate division

Cell Cycle Checkpoints

G1, S, G2, M

G1 failure leads to G0 phase

Cells do not replicate and stay in G0

Prophase

Chromatin forms chromosomes

Nucleolus disappears

Two centrosomes move to opposite poles to begin forming mitotic spindles

Prometaphase

Nuclear envelope degrades exposing chromosomes to cytoplasm

Mitotic spindles link to chromosomes by attaching to kinetochore proteins

Metaphase

Mitotic spindles align chromosomes at the middle of the cell in a single row

Anaphase

Sister chromatids are pulled apart towards opposite ends

Some parts of the mitotic spindle stretch, lengthening the cell

Telophase

Chromosomes revert back to chromatin

Mitotic spindles degrade

Nucleolus and nuclear envelope reform at each end to form 2 nuclei

Cytokinesis

Division of cytoplams

1 → 2 cells

Cleavage furrow

Formed during cytokinesis

In animal cells the indentation where cells separate

Cell plate

In plants vesicles carry materials to generate a cell plate to separate daughter cells