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| Life cycle | The entire sequence of stages in the life of an organism, from the adults of one generation to the adults of the next |
| Sexual reproduction | The creation of offspring by the fusion of two haploid sex cells (gametes) forming a diploid zygote |
| Genome | A complete (haploid) set of an organism's genes; an organism's genetic material |
| Asexual reproduction | The creation of offspring by a single parent, without the participation of sperm and egg |
| Chromosomes | A threadlike, gene-carrying stucture found in the nucleus of all eukaryotic cells and most visible during mitosis and meiosis. Chromosomes consist of DNA and protein |
| Cell division | The reproduction of cells |
| Binary fission | A means of asexual reproduction in which a parent divides any two individuals of about equal size |
| Chromatin | Diffuse, very long, coiled fibers of DNA with proteins attached, the form taken by the chromosomes when a eukaryotic cell is not dividing |
| Somatic cells | Any cell in a multicellular organism except a sperm or egg cell or a cell that develops into a sperm or egg |
| Sister chromatids | One of the two identical parts of a duplicated chromosome in a eukaryotic cell. Consisting of copies of a long, coiled DNA moleucle with associated proteins, sister chromatids are jointed at the centromere of the chromosome. |
| Centromere | The region of a chromosome where two sister chromatids are joined and where spindle microtubles attach tot he chromosome during mitosis and meiosis. The centromere divides at the onset of anaphase during mitosis and anaphase II of meiosis |
| Cell cycle | An orderly sequence of events (including interphase and the mitotic phase) from the time a eukaryotic cell divides to form two daughter cells to the time those daughter cells divide again |
| Interphase | The period in the eukaryotic cell cycle when the cell is not actually dividing |
| Mitosis | The division of a single nucleus into two genetically identical daughter nuclei. Mitosis and cytokinesis make up the mitotic (M) phase of the cell cycle |
| Cytokinesis | The division of the cytoplasm to form two separate daughter cells. Cytokinesis usually occurs together with telephase of mitosis, and the two processes make up the mitotic (M) phase of the cell cycle |
| Mitotic phase (M) | mitosis and cytokinesis |
| Prophase | The first stage of mitosis, during which duplicated chromosomes condense from chromatin, and the mitotic spindle forms and begins moving the chromosomes toward the center of the cell |
| Metaphase | The second phase of mitosis. During metaphse, all the cell's duplicated chromosomes are lined up at an imaginary plane equidistant between the poles of the mitotic spindle |
| Anaphase | The third stage of mitosis, beginning when the centromeres of duplicated chromosomes divide and sister chromatids separate from each other, and ending when a complete set of daughter chromosomes are located at each of the two poles of the cell |
| Telophase | The fourth and final stage of mitosis, during which daughter nuclei form at the two poles of a cell. Telophase usually occurs together with cytokinesis |
| Mitotic spindle | A spindle-shaped structure formed of microtubles and associated proteins that is involved in the movements of chromosomes duirng mitosis and meiosis |
| Microtuble organizing center (MTOC) | A specialized place in the cell where microtubles of the mitotic spindle begin to form |
| Cleavage furrow | The first sign of cytokinesis during cell division in an animal cell; a shallow groove in the cell surface near the old metaphse plate |
| Cell plate | A double membrane across the midline of a dividing plant cell, between which the new cell wall forms during cytokinesis |
| Anchroage dependence | Keeps cells from dividing inappropriately |
| Density-dependent inhibition | The arrest of cell division that occurs when cells grown ina laboratory dish touch one another, generally due to an inadequate supply of growth factors |
| Growth factor | A protein secreted by certain body cells that stimulates other cells to divide |
| Cell-cycle control system | A cyclically operating set of proteins that triggers and coordinates events in the eukaryotic cell cycle |
| Cancer cells | A cell that is not subject to normal cell-cycle control mechanisms and that will divide continuously, often killing the organism if unchecked |
| Tumor | An abnormal mass of cells that forms within ortherwise normal tissue |
| Benign tumor | An abnormal mass of cells that remains as its original site in the body |
| Malignant tumor | An abnormal tissue mass that can be spread into neighboring tissue and to other parts of the body; a cancerous tissue |
| Metastasis | The spread of cancer cells beyond their original site |
| Carcinomas | Cancer that originates in the coverings of the body, such as the skin or linings of the intestinal tract |
| Sarcoma | Cancer of the supportive tissues, such as bone, cartilage, and muscle |
| Leukemia | A type of cancer of the blood-forming tissues, characterized by an excessive production of white blood cells and an abnormally high number of the in the blood; cacer of the bone marrow cells that produce leukocytes |
| Lymphoma | Cancer of the tissues that form white blood cells |
| Homologus chromosomes | The two chromosomes that make up a matched pair in a diploid cell. Homologus chromosomes are of the same length, centromere position, and staining pattern and posess genes or the same characteristics at corresponding loci. One homologous chromosome is inherited from the organisms father, the other from the mother |
| Locus | The particular site where a gene is found on a chromosome. Homologus chromosomes have corresponding loci |
| Autosomes | A chromosome not directly involved in determining the sex of an organism |
| Sex chromosomes | A chromosome that determines wheter an individual is male or female |
| Diploid cells | In an organism that reproduces sexually, a cell containing two homologus sets of chromosomes, one set inherited from each parent |
| Gametes | A sex cell; a haploid egg or sperm |
| Haploid cell | In the life cycle of an organism that reproduces sexually. a cell containing a single set of chromosomes |
| Fertilization | The union of the nucleus of a sperm cell with the nucleus of an egg cell, producing a zygote |
| Zygote | The fertilized egg, which is diploid, that results from the union of a sperm cell nucleus and an egg cell nucleus |
| Meiosis | In a sexually reproducing organism, the division of a single diploid nucelus into four haploid daughter nuclei. Meiosis and cytokinesis produce haploid gametes from diploid cells in teh reproductiver organs of the parents |
| Crossing over | exchange of corresponding segments between two homologous chromosomes |
| Chiasma | The microscopically visible site where crossing over has occurred between chromatids of homologous chromosomes during prophase I of meiosis |
| Genetic recombination | The production, by crossing over, of chromosomes with gene combinations different from those in the origianl chromosomes |
