5.2 Mitosis and CytokinesisChapter 5 Cell Growth and Division

Mr. Shilala

DAHS

KEY CONCEPT Cells divide during mitosis and cytokinesis.

DNA and Chromosomes• DNA is a double stranded molecule made of four

subunits called nucleotides• A chromosome is one long continuous thread of

DNA– Consists of numerous genes with regulatory information– Your cells have 46 chromosomes– If stretched out straight and laid end to end DNA in one cell would

be about 10 feet long

Chromosomes condense at the start of mitosis.• DNA is loosely organized during interpahse

– Looks like spaghetti

• DNA wraps around proteins (histones) that condense (shrink) it.

• DNA plus proteins is called chromatin

DNA doublehelix

DNA andhistones Chromatin

SupercoiledDNA

• Chromatid• One half of a duplicated

chromosome is a chromatid.• Sister chromatids (identical

chromatids) are held together at the centromere.

• Telomeres protect DNA and do not include genes.- Prevent chromosomes from

accidentally attaching to each other

Condensed, duplicated chromosome

chromatid

telomere

centromere

telomere

Parent cell

centrioles

spindle fibers

centrosome

nucleus withDNA

• Interphase prepares the cell to divide.

• During interphase, the DNA, or chromosomes, are duplicated.

Mitosis and cytokinesis produce two genetically identical daughter cells.

Mitosis• Mitosis divides the cell’s nucleus into 2

genetically identical nuclei in four stages– Each has full set of DNA

• IPMAT– Interphase

• Not part of mitosis

– Prophase – Metaphase– Anaphase– Telophase

• Prophase– DNA and Proteins condense into Chromosomes – Nuclear membrane breaks down, centrioles

move to opposite poles and spindle fibers form

• Metaphase– Chromosomes line up in the middle of the cell.– Spindle fibers attach to each chromosome

• Anaphase– Sister chromatids separate to opposite sides of

the cell.

• Telophase– New nuclei form– Chromosomes begin to uncoil – Spindle fibers fall apart.

• Cytokinesis– Cytokinesis is the division

of the cytoplasm into two cells

– In animal cells, the membrane pinches closed.

– In plant cells, a cell plate forms

Youtube Mitosis Video