Chapter 9Cell Cycle and

Mitosis

You Must Know

• The structure of the duplicated chromosome.• The events that occur in the cell cycle (G1, S,

and G2)• The features of mitosis that result in the

production of genetically identical daughter cells including replication, alignment of chromosomes (metaphase), and separation of chromosomes (anaphase).

video

• Mitosis

Figure 9.1 – Chromosomes during cell division

Eukaryotic chromosomes consist of chromatin, a complex of DNA and protein.

Every eukaryotic species has a characteristic number of chromosomes in each cell nucleus.

Somatic cells (nonreproductive cells) have two sets of chromosomes. They are diploid.

Gametes (reproductive cells: sperm and eggs) have one set of chromosomes. They are haploid.

Replicated Chromosome

Centromere 0.5 m

Sisterchromatids

Centromere

ChromosomalDNA moleculesChromosomes

Chromosomearm

1

Sisterchromatids

Chromosomearm

Chromosome duplication

2

Separation of sisterchromatids

3

One chromosome and one DNA molecule.

One chromosome and two DNA molecules.

Two chromosomes and two DNA molecules.

• Eukaryotic cell division consists of– Mitosis, the division of the genetic material in the

nucleus– Cytokinesis, the division of the cytoplasm

• Gametes are produced by a variation of cell division called meiosis.

• Meiosis yields nonidentical daughter cells that have only one set of chromosomes, half as many as the parent cell. (Haploid cells)

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The Cell Cycle

Cytokin

esis

Mito

sis

S(DNA synthesis)G1

G2

• Mitosis is conventionally divided into five phases– Prophase– Prometaphase– Metaphase– Anaphase– Telophase

• Cytokinesis overlaps the latter stages of mitosis

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Figure 9.7c

Centrosomes(with centriolepairs)

G2 of Interphase Prophase

Chromosomes(duplicated,uncondensed)

Early mitoticspindle

CentromereAster

NucleolusPlasmamembrane Two sister chromatids of

one chromosomeNuclearenvelope

Figure 9.7d

PrometaphaseFragmentsof nuclearenvelope

Nonkinetochoremicrotubules

Kinetochoremicrotubule

Kinetochore Spindle Centrosome atone spindle pole

Metaphaseplate

Metaphase

Figure 9.7e

Anaphase Telophase and Cytokinesis

Cleavagefurrow

Nucleolusforming

Nuclearenvelopeforming

Daughterchromosomes

Cytokinesis in an animal cell

Contractile ring ofmicrofilaments

Cleavage furrow

Daughter cells

100 m

New cell wall

Daughter cells

Cell plate

Wall of parentcell

Vesiclesformingcell plate

1 m

Cytokinesis in a plant cell

Figure 9.11

10 m

Nucleus

Telophase

NucleolusChromosomescondensing Chromosomes

Prometaphase

Cell plate

Prophase

AnaphaseMetaphase

1 2

3 4 5