KEY CONCEPT Cells divide during mitosis and cytokinesis.

Chromosomes condense at the start of mitosis. DNA wraps around proteins (histones) that condense it. DNA double helix DNA and histones Chromatin Supercoiled DNA

DNA Double Helix Each continuous double-stranded DNA molecule makes one chromosome

DNA and histones DNA wraps at regular intervals around proteins called histones forming chromatin.

Chromatin Interactions between parts of the histones further compact the DNA.

Supercoiled DNA The chromatin coils more and more tightly around organizing proteins.

DNA plus proteins (histones) is called chromatin. chromatid telomere centromere One half of a duplicated chromosome is a chromatid. Sister chromatids are held together at the centromere. Telomeres protect DNA and do not include genes. Condensed, duplicated chromosome

Interphase prepares the cell to divide. Mitosis and cytokinesis produce two genetically identical daughter cells. Parent cell centrioles spindle fibers centrosome nucleus with DNA Interphase prepares the cell to divide. During interphase, the DNA is duplicated. G1, S, G2

Mitosis divides the cell’s nucleus in four phases. During prophase, chromosomes condense and spindle fibers form. Nuclear envelope begins to break down.

Mitosis divides the cell’s nucleus in four phases. During metaphase, chromosomes line up in the middle of the cell. Centrioles move to opposite poles of the cell. Spindle fibers elongate.

Mitosis divides the cell’s nucleus in four phases. During anaphase, sister chromatids separate to opposite sides of the cell.

Mitosis divides the cell’s nucleus in four phases. During telophase, the new nuclei form and chromosomes begin to uncoil.

Cytokinesis differs in animal and plant cells. In animal cells, the membrane pinches closed. In plant cells, a cell plate forms.