5.2 Mitosis

•Describe Interphase•Know the phases of mitosis•Know Cytokinesis

Cell Cycle

1. Interphase2. Mitosis3. Cytokinesis

Interphase (cell cycle)

• Not dividing• Growth and preparation

Interphase (cell cycle)

1. G1 (gap 1) – growth2. S (synthesis) – chromosomes

replicate3. G2 (gap 2) –new organelles

Interphase

Chromosome replication1. Chromatin coils/ twists to form a

chromosome2. Chromosome makes a copy3. Sister chromatids formed

Question:Question:What is a What is a chromosomechromosome??

Answer:Answer:

• A chromosomechromosome is made up of a DNADNA - histone protein histone protein complex called chromatinchromatin.

• ChromatinChromatin is a long, thin fiber that is folded and coiled to form chromosomeschromosomes.

DNA double helix

Histone proteins

chromosome

Question:Question:

• What is a replicated What is a replicated chromosomechromosome??

Answer:Answer:

• A replicated chromosomechromosome consist of two strands of identical chromosomal material called chromatidschromatids (sister sister chromatidschromatids).

chromatid

chromatid

S phase: chromosomes replicate

chromosome

chromosome

centromere

Question:Question:

• When is a When is a chromatid a chromatid a chromatidchromatid??

Answer:Answer:

• A chromatidchromatid is a chromatidchromatid as long as it is held in association with a sistersister chromatidchromatid at the centromerecentromere.

chromatid

chromatid

centromere

chromosome

Mitosis

Follows Interphase in the cell cycle1. Prophase2. Metaphase3. Anaphase4. Telophase

Prophase - 1

• Nuclear membrane breaksdown• Centrioles move to poles• Spindle fibers form• Sister chromatids are held together

centromeres

Metaphase -2

• Centromeres attach to fibers• Pull chromosomes to the center on

the “metaphase plate”

Anaphase - 3

• Centromeres divide sister chromatids• Chromatids move to opposite poles

of the cell

Telophase - 4

• Chromosome fully divided into 2 new cells

• 2 nuclei and nuclear membrane form• Chromosomes uncoil to form

chromatin

Cytokinesis

• Follows mitosis in the cell cycle• Cytokinesis = division of cytoplasm• Cell membranes start to split• 2 new cells are formed

Cytokinesis – Animal

• Animal cell – pinches off its membrane to form 2 new cells

• 24 hours after fertilization

• Plant cell – Cell wall is being formed between 2 plant cells

• Cell plate forms new cell membranes

Cytokinesis - plant

• Plant cell – Cell wall is being formed between 2 plant cells

• Cell plate forms new cell membranes