Cell Reproduction

Somatic cells: body cells.

Human somatic cells contain 46 chromosomes (23 pair)

Gametes: sex cells used in sexual reproduction.

Chromosomes

Chromatid: 2 joined strands; each is a duplicate of its partner

Centromere: point where chromatids are held together; also attaches chromosome to the microtubules of the spindle fiber

Homologous chromosomes: chromosomes that contain the same kind of information but come from different parents.

Cell Reproduction

Mitosis: The type of cell division in which the major event is nuclear division.

Occurs in eukaryotes.

Necessary for growth, healing wounds, repairing injured body parts.

Cytokinesis: cytoplasmic division that follows nuclear division

Interphase: period of cell growth, DNA synthesis, and preparation for cell division.

non-reproducing stage in which a cell spends most of its life

phase in which a cell prepares itself for cell division

begins when cell reproduction is completed

duplicates genetic material; so at the end each cell has two sets

assembles structures and organelles

G1 Phase: cell growth phase.

S Phase: DNA replicates.

G2 Phase: preparation for mitosis. Cell organelles duplicated, cell increases in size.

Prophase

First phase of mitosis.

Chromatin begins to coil into chromosomes, becoming visible.

The nuclear membrane begins to dissolve.

In animal cells, 2 pairs of centrioles separate and move to opposite poles of the cell.

Microtubules form in between the centrioles and become spindle fibers.

Metaphase

second stage of mitosis

chromosomes become attached to the spindle

chromosomes line up along the equator of the cell

Anaphase

third stage of mitosis

paired chromatids are pulled apart at the centromere and move to opposite poles of the cell

as anaphase ends, there is one set of single-stranded chromosomes at each end of the cell

Telophase: chromosomes begin to uncoil, nuclear membrane begins to reform.

fourth and last stage of mitosis

two cells begin to form from one

nuclear membrane reforms and encloses chromosomes

nucleoli reappears

chromosomes lose distinct outline and appear as a mass of chromatin

Cytokinesis

Division of the cytoplasm.

Animal cells form a cleavage furrow.

Plant cells form a cell plate.

2 new daughter cells are formed.

Most cells complete mitosis in one to two hours.

Approximately 25 million cell divisions occur every second in the adult human body.

Cancer is a rapid, uncontrolled division of one kind of cell that invades and disrupts cells in other tissues.

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