All cells come from cells. Eukaryotes and Prokaryotes reproduce differently.

Bacterial Cell Division Binary fission:

Eukaryotic Cell Division Except for gametes, most eukaryotic cells are formed by mitosis.

Eukaryotic Cell Division Chromosomes: 1. rod shaped masses of chromatin (DNA + histone proteins) 2. found in the nucleus

3. histone proteins (11.3) a. + charge b. form (+) spools around which DNA winds

Chromosomes normally exist as homologous pairs. Organisms with paired chromosomes are called diploid.

Cell Cycle 1. Daughter cells continue to divide. 2. Genetic information is passed on through the generations. 3. 2 major phases:

Interphase 1. cell is not dividing 2. protein synthesis, growth, normal activities 3. 3 major phases:

Chromatids 1. Duplicated chromosomes, joined at a centromere - only after S phase 2. The two chromatids contain identical DNA. 3. Each chromatid will be a chromosome in the new daughter cell.

Prophase Nuclear membrane fades and nucleoli disappear. Chromatids tightly coiled and visible. Centrosomes move to opposite poles of the cell. Mitotic spindle begins to form.

Metaphase 1. Orderly alignment of chromosomes. 2. On equatorial plane (metaphase plate). 3. Spindle microtubules now radiating from centromeres to centrioles.

Anaphase 1. Begins when centromeres split. 2. Chromatids become physically separated, now chromosomes. 3. Spindle fibers “shorten”, pulling chromosomes toward centrioles. 4. Each “pole” receives 46 chromosomes.

Telophase 1. Final stage of mitosis. 2. Reverse of prophase. a. chromosomes uncoil b. nuclear membrane reappears c. nucleoli reappear

Telophase Results in two daughter nuclei.

Cytokinesis 1. Usually begins during anaphase. 2. Infolding of plasma membrane, forming cleavage furrow.

Cytokinesis (cont.) 3. Plants form a centrally located cell plate. “inside-out”