5.2 Mitosis and Cytokinesis LEQ: How do eukaryotic cells divide?

• Key terms –

interphase, chromosome, chromatin, phases of mitosis (various), cytokinesis

• Reading 5.3

5.2 Mitosis and Cytokinesis LEQ: How do eukaryotic cells divide?

• Activator: • During which stage of the cell cycle is DNA copied? Explain how this process occurs.

5.2 Mitosis and Cytokinesis

5.2 Mitosis and Cytokinesis Chromosomes condense at the start of mitosis.

• A

chromosome

is a DNA molecule associated with protein.

• DNA wraps around

histone

proteins that condense it.

DNA double helix DNA and histones Chromatin Supercoiled DNA

• Chromosomes come in

duplicated

and

unduplicated

forms

5.2 Mitosis and Cytokinesis chromatid

• • • •

Chromatin –

DNA coiled around histone proteins

Chromatid -

One half of a duplicated chromosome

Sister chromatids

(duplicated, right) - are held together at the

centromere

.

Telomeres (ends) -

protect DNA and do not include genes.

telomere centromere telomere Condensed, duplicated chromosome

5.2 Mitosis and Cytokinesis

5.2 Mitosis and Cytokinesis Focus on Mitosis:

• The nucleus – when is it disassembled, when does it reappear?

• Chromosomes – how do they move, when do chromatids separate?

• Mitotic Spindle – how does it assist in mitosis?

5.2 Mitosis and Cytokinesis Mitosis and cytokinesis produce two genetically identical daughter cells in many eukaryotes.

Parent cell

•

Interphase

prepares the cell to divide.

centrioles

– G1 – S – G2

spindle fibers centrosome nucleus with DNA

5.2 Mitosis and Cytokinesis

•

Mitosis

divides the cell’s nucleus in four phases: –

Prophase

- chromosomes condense, nucleus disassembles, spindle fibers form.

5.2 Mitosis and Cytokinesis

–

Metaphase

- chromosomes line up in the middle of the cell.

5.2 Mitosis and Cytokinesis

–

Anaphase

: sister chromatids separate, move to opposite sides of the cell.

5.2 Mitosis and Cytokinesis Focus: Anaphase chromosomes

5.2 Mitosis and Cytokinesis

–

Telophase

- nuclei form, spindle disassembles and chromosomes begin to uncoil.

5.2 Mitosis and Cytokinesis

•

Cytokinesis

differs in animal and plant cells.

– Animals: the membrane pinches closed.

– Plants: a cell wall forms.

5.2 Mitosis and Cytokinesis

5.2 Mitosis and Cytokinesis

5.2 Mitosis and Cytokinesis

5.2 Mitosis and Cytokinesis A look ahead: Lab

• Interphase • “I-ball”

nucleus with DNA Parent cell centrioles spindle fibers centrosome

5.2 Mitosis and Cytokinesis

• Prophase • “pile”

5.2 Mitosis and Cytokinesis

• Metaphase • “middle”

5.2 Mitosis and Cytokinesis

• Anaphase • “apart”

5.2 Mitosis and Cytokinesis

• Telophase • “two piles”

5.2 Mitosis and Cytokinesis Summary:

• Briefly explain why the daughter cells resulting from binary fission and mitosis are genetically identical to each other and to the original cell.

• How does mitosis accomplish the production of daughter cells.

– Be sure to address how genetic information is acquired

5.2 Mitosis and Cytokinesis Answers:

• Daughter cells are clones, the genetic information of the parent cell was copied and condensed into duplicated chromosomes, each consisting of two identical DNA molecules (sister chromatids). The chromatids are then separated during metaphase so that when the daughter cells begin to assemble their nuclei, each will have received a complete copy of the parent cell’s genetic information.

• Prophase and telophase are opposites. The nuclear envelope fragments, chromosomes condense, and spindle fibers start to assemble in prophase. In telophase, the reverse occurs: the nuclear envelope reforms, chromosomes uncoil, and spindle fibers disassemble.