The Cell & Mitosis Cycle

Cell Division

The reproduction of cells.

Cell Cycle

The life of a cell from its formation to its own division.

Genome

All the DNA in a cell, constituting the full genetic code containing all the genes.

Chromosomes

The structures into which DNA molecules in a cell are packaged.

Histones

Proteins around which DNA undergoes several levels of coiling during cell replication.

Chromatin

The combined DNA and protein material.

Karyotype

A sorted set of microscope photos of all the chromosomes in a cell.

Homologous Pairs

Pairs of chromosomes with one inherited from each parent.

Homologous Chromosomes

Pairs of chromosomes, one from each parent, that carry the same genes, but not necessarily the same versions of those genes.

Sister Chromatids

Connected, identical copies of a duplicated chromosome.

Centromere

The narrow "waist" of the duplicated chromosome, where the two chromatids are most closely attached.

Somatic Cells

Typical cells of the body that contain the full genome or full set of chromosomes.

Gametes

Reproductive cells, including sperm and eggs, that contain half the chromosomes found in somatic cells.

Meiosis

A variation of cell division that yields nonidentical daughter cells with only one set of chromosomes (half as many as the parent cell).

Interphase

The phase of the cell cycle comprising about 90% of the cycle, involving cell growth and copying of chromosomes in preparation for division.

Mitosis

The separation of duplicated chromosomes.

Mitotic Spindle

A structure made of microtubules that controls chromosome movement during mitosis.

Aster

A radial array of short microtubules that extends from protein hubs in the spindle.

Centrosomes

Protein hubs in the spindle from which asters extend.

Kinetochore

A protein at the centromere of each sister chromatid to which the microtubules of the spindle attach.

Metaphase Plate

A plane equal distance from the two centrosomes where chromosomes align during metaphase.

Cleavage

The process by which cytokinesis (the splitting of one cell into two) occurs in animal cells, forming a cleavage furrow.

Cell Plate

A structure that forms during cytokinesis in plant cells to divide the cell.

Binary Fission

A type of cell division used by prokaryotes (bacteria and archaea) to reproduce.

Cell Cycle Control System

A distinct system that directs the sequential events of the cell cycle, similar to a clock.

Checkpoints

Specific places in the cell cycle "clock" where the cycle stops until a go-ahead signal is received.

G0 Phase

A nondividing state that a cell switches into if it does not receive the go-ahead signal at a checkpoint.

Growth Factors

Proteins released by cells that stimulate other cells to divide.

Cancer Cells

Cells that have escaped the regulation of controls on the cell cycle and may not need growth factors to grow and divide.