Term | Definition |
cell cycle | An ordered sequence of events in eukaryotes that involves cell growth and nuclear division; consists of the stages Gp, S, G2, and M. |
interphase | Stages of the cell cycle (Gp S, G2) during which growth and DNA synthesis occur when the nucleus is not actively dividing. |
chromatid | Following replication, a chromosome consists of a pair of sister chromatids, held together at the centromere; each chromatid is comprised of a single DNA helix. |
sister chromatid | One of two genetically identical chromosomal units that are the result of DNA replication and are attached to each other at the centromere. |
mitosis | The stage of cellular reproduction in which nuclear division occurs; process in which a parent nucleus produces two daughter nuclei, each having the same number and kinds of chromosomes as the parent nucleus. |
cytokinesis | Division of the cytoplasm following mitosis or meiosis. |
mitotic spindle | A complex of microtubules and associated proteins that assist in separating the chromatids during cell division. |
signal | Molecule that stimulates or inhibits an event in the cell. |
growth factor | A hormone or chemical, secreted by one cell, that may stimulate or inhibit growth of another cell or cells. |
apoptosis | Programmed cell death; involves a cascade of specific cellular events leading to death and destruction of the cell. |
somatic cell | Body cell; excludes cells that undergo meiosis and become sperm or eggs. |
cyclin | Protein that cycles in quantity as the cell cycle progresses; combines with and activates the kinases that promote the events of the cycle. |
euchromatin | Chromatin with a lower level of compaction and therefore accessible for transcription. |
heterochromatin | Highly compacted chromatin that is not accessible for transcription. |
diploid (2n) | Cell condition in which two of each type of chromosome are present. |
haploid (n) | Cell condition in which only one of each type of chromosome is present. |
centromere | Constriction where sister chromatids of a chromosome are held together. |
kinetochore | An assembly of proteins that attaches to the centromere of a chromosome during mitosis. |
centrosome | Central microtubule organizing center of cells. In animal cells, it contains two centrioles. |
centriole | Cell structure, existing in pairs, that occurs in the centrosome and may help organize a mitotic spindle for chromosome movement during animal cell division. |
prophase | First phase of mitosis; characterized by the condensation of the chromatin; chromosomes are visible, but scattered in the nucleus. |
prometaphase | Second phase of mitosis; chromosomes are condensed but not fully aligned at the metaphase plate. |
metaphase | Third phase of mitosis; chromosomes are aligned at the metaphase plate. |
anaphase | Fourth phase of mitosis; chromosomes move toward the poles of the spindle. |
telophase | Final phase of mitosis; daughter cells are located at each pole. |
cleavage furrow | Indentation in the plasma membrane of animal cells during cell division; formation marks the start of cytokinesis. |
cell plate | Structure across a dividing plant cell that signals the location of new plasma membranes and cell walls. |
therapeutic cloning | Used to create mature cells of various cell types. Facilitates study of specialization of cells and provides cells and tissue to treat human illnesses. |
reproductive cloning | Used to create an organism that is genetically identical to the original individual. |
cancer | Malignant tumor whose nondifferentiated cells exhibit loss of contact inhibition, uncontrolled growth, and the ability to invade tissue and metastasize. |
benign | Mass of cells derived from a single mutated cell that has repeatedly undergone cell division but has remained at the site of origin. |
malignant | The power to threaten life; cancerous. |
tumor | Cells derived from a single mutated cell that has repeatedly undergone cell division; benign tumors remain at the site of origin, while malignant tumors metastasize. |
metastasis | Spread of cancer from the place of origin throughout the body; caused by the ability of cancer cells to migrate and invade tissues. |
angiogenesis | Formation of new blood vessels; rapid angiogenesis is a characteristic of cancer cells. |
proto-oncogene | Gene that promotes the cell cycle and prevents apoptosis; may become an oncogene through mutation. |
tumor suppressor gene | Gene that codes for a protein that ordinarily suppresses the cell cycle; inactivity due to a mutation can lead to a tumor. |
oncogene | Cancer-causing gene formed by a mutation in a proto-oncogene; codes for proteins that stimulate the cell cycle and inhibit apoptosis. |
telomere | Tip of the end of a chromosome that shortens with each cell division and may thereby regulate the number of times a cell can divide. |
asexual reproduction | Reproduction that requires only one parent and does not involve gametes. |
nucleoid | Region of prokaryotic cells where DNA is located; it is not bound by a nuclear envelope. |
binary fission | Splitting of a parent cell into two daughter cells; serves as an asexual form of reproduction in bacteria. |