| Term | Definition |
|---|
| Nucleus | contains most of the genes in the eukaryotic cell |
| Nuclear Envelope | porous, double membrane that encloses the nucleus |
| Chromosomes | coiled up/condensed structures (chromatin) that contains genetic information |
| Chromatin | a complex of protein and DNA, much looser than chromosomes |
| Nucleolus | zone in the nucleus where rRNA is synthesized as well as ribosomal subunits |
| Mitosis | a process of nuclear division in eukaryotic cells, which produces 2 identical daughter cells |
| Interphase | the cell spends 90% of the cycle in this phase, during which the cell grows, copies its chromosomes (chromatin form) and double its organelles in preparation for cell division (G1,S,G2) |
| Somatic Cells | all body cells except for reproductive cells |
| Sister Chromatids | Two chromatids containing an identical DNA molecule |
| Centromere | a specialized region where the sister chromatids are most closely attached |
| G1 phase | a growth period (first part of interphase) |
| S phase | chromosomes replicate (2nd part of interphase) |
| G2 phase | another growth period (3rd part of interphase) |
| Prophase | chromatin tightens up and becomes chromosomes, nucleoli dissapear, sister chromatids form, the mitotic spindle begins to form |
| Prometaphase | the nucleur envelope fragments, the spindle microtubules attach to the kinetochores |
| Kinetochore | a structure of proteins attached to a chromatid at the centromere, it attaches to the spindle microtubules |
| Metaphase | longest stage of mitosis, the chromosomes convene at the center of the cell, the centromeres are directly at the center |
| Anaphase | shortest phase of mitosis, the sister chromatids are separated, the liberated chromosomes move to opposite ends of the cell |
| Telophase | two daughter nuclei form, nuclear envelopes arise, chromosomes become less condensed, final stage of mitosis |
| Cytokinesis | the division of the cytoplasm, in animal cells the cleavage furrow pinches the two cells in two |
| Mitotic Spindle | begins to form during prophase, an assemblage of microtubules and associated proteins that is involved in the movements of chromosomes during mitosis |
| Cleavage Furrow | the first sign of cleavage in an animal cell; a shadown groove in the cell surface near the old metaphase plate |
| Cell Plate | a double membrane across the mid-line of a dividing plant cell, between which the new cell wall forms during cytokinesis |
| Cleavage | the process of cytokinesis in animal cells, characterized by pinching of the plasma membrane |
| Cells that Regularly Divide | blood cells and skin cells |
| Cells that Rarely/Never Divide after Maturity | nerve cells and muscle cells |
| Stem Cell | any relatively unspecialized cell that can produces, during a single division, one identical daughter cell and one more specialized daughter cell that can undergo further differentiation (totipotent, pluripotent, multipotent, terminally differentiated) |
| Totipotent | (zygote) describing a cell that can give rise to all parts of the embryo and adult, as well as extraembryonic membranes in species that have them |
| Pluripotent | (embryo) describing a cell that can give rise to many, but not all, parts of an organism |
| Multipotent | (adult) a cell that can give rise to many, but not all, parts of an organism...even more limited that pluripotent cells |
| Making Embryonic Pluripotent Stem Cells | in vitro fertilized egg, blastocyst stage (5-7 days old), inner stem cell mass, cultured undifferentiated stem cells, specialized cells (blood cells, neural cells, muscle cells) |
| Therapeutic Cloning | remove nucleus from the donor's egg, add adult cell into enucleated egg, clone the embryo, isolate embryonic stem cells from the cloned embryo, treat patient with matched cells |
| Stembrids | remove nuclei from existing embryonic stem cell line, fuse adult cells with enucleated embryonic stem cells, new embryonic stem cells are created, treat patient with matching cells |
| G0 Phase | a nondividing state occupied by cells that have left the cell cycle |
| Cell Cycle Control System | a cyclically operating set of molecules in the eukaryotic cell that both triggers and coordinates key events in the cell cycle |
| Checkpoint | a control point in the cell cycle where stop and go-ahead signals can regulate the cycle (G1, G2, M) |
| G1 Checkpoint | "restriction point", if a cell receives a go-ahead signal at the checkpoint, it will complete the G1,S,G2, and M phases and divide, if it does not receive a go-ahead signal at that point, it will exit the cycle, switching into the G0 phase |
| Cyclin | a cellular protein that occurs in a cyclically fluctuating concentration and that plays an important role in regulating the cell cycle |
| Cyclin-Dependent Kinase | a protein kinase that is active (phosphorylates other molecules) only when attached to a particular cyclin |
| MPF | Maturation-promoting factor (M-phase promoting factor); a protein complex required for a cell to progress from late interphase to mitosis, the active form consists of cyclin and a protein kinase |
| Growth Factor | a protein relased by certain cells that stimulates other cells to divide |
| Density-Dependent Inhibition | the phenomenon observed in normal animal cells that causes them to stop dividing when they come into contact with one another |
| Anchorage-Dependence | the requirement that a cell must be attached to the substratum in order to divide |
| Transformation | the conversion of a normal animal cell to a cancerous cell |
| Benign Tumor | a mass of abnormal cells that remains at the site of origin |
| Malignant Tumor | a cancerious tumor that is invasive enough to impair the functions of one or more organs |
| Metastasis | the spread of cancer cells to locations distant from their original site |
| Cancer Cells | growth factors not needed, density-dependent inhibition not exhibited, a tumor forms (benign vs malignant), anchorage dependence not exhibited, metastasis (spreading), de-defferentiated cells, loss of metabolic function |
| Oncogene | a gene found in viral or cellular genomes that is involved in triggering molecular events that can lead to cancer |
| Proto-oncogene | a normal cellular gene that has the potential to become an oncogene, codes for products that promote cell division [growth factors, growth factor receptors, signaling molecules (cyclins, cyclin dependent kinases)] |
| Tumor-Suppressor Gene | a gene whose protein product inhibits cell division, thereby preventing the uncontrolled cell growith that contributes to cancer |
| From Proto-Oncogene to Oncogene | translocation or transposition (gene moved to new locus, under new controls), gene amplification (multiple copies of the gene), point mutation (within a control element) (within the gene) |
| Cell Cycle-Stimulating Pathway (Ras) | Ras is an oncogene....the pathway is triggered by a growth factor that binds to its receptor in the plasma membrane, the signal is relayed to a G protein called Ras, Ras is active when GTP is bound to it, Ras passes the signal to a series of protein kinases, the last kinase activates a transcription activator that turns on one or more genes for proteins that stimulate the cell cycle, if a mutation makes Ras or any other pathway component abnormally active, excessive cell division and cancer may result |
| Cell Cycle-Inhibiting Pathway (p53) | P53 is a tumor suppressor gene ... in this pathway, DNA damage is an intracellular signal that is passed via protein kinases and leads to activation of p53, activated p53 promotes transcription of the gene for a protein that inhibits the cell cycle, the resulting suppression of cell division ensures that the damanged DNA is not replicated, mutations causing deficiencies in any pathway component can contribute to the development of cancer |
| Ras gene | a gene that codes for Ras, a G protein that relays a growth signal from a growth factor receptor on the plasma membrane to a cascade of protein kinases, ultimately resulting in stimulation of the cell cycle |
| p53 gene | a tumor-suppressor gene that codes for a specific transcription factor that promotes the synthesis of cell cycle-inhibiting proteins |
| Development of Colorectal Cancer | loss of tumor suppressor gene APC (or other) -----small benign growth (polyp)----->, activation of ras oncogene / loss of tumor-suppressor gene DCC ----- larger benign growth (adenoma) ------> loss of tumor-suppressor gene p53 / additional mutations ------> malignant tumor (carcinoma) |
| Gamete | a haploid reproductive cell, such as an egg or sperm, gametes unite during sexual reproduction to produce a diploid zygote |
| Locus | a specific place along the lenght of a chromosome where a given gene is located |
| Asexual Reproduction | (offspring produced by mitosis) the generation of offspring from a single parent that occurs without the fusion of gametes (by budding division of a single cell, or division of the entire organism into two or more parts), in many but not all cases, the offspring are genetically identical to the parent |
| Clone | a lineage of genetically identical individuals or cells |
| Sexual Reproduction | (gametes produced by meiosis) a type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from the gametes of the two parents |
| Life Cycle | the generation-to-generation sequence of stages in the reproduction history of an organism |
| Somatic Cell | any cell in a multicellular organism except a sperm or egg cell |
| Homologous Chromosomes | a pair of chromosomes of the same lenght, centromere position, and staining pattern that possess genes for the same characters at corresponding loci, one homologous chromosome is inherited from the organism's father the other from the mother, also called homologs, or a homologous pair |
| Sex Chromosomes | a chromosome responsible for determining the sex of an individual |
| Autosome | a chromosome that is not directly involved in determining sex; not a sex chromosome |
| Diploid Cell | a cell containing two sets of chromosomes (2n), one set inherited from each parent |
| Haploid Cell | a cell containing only one set of chromosomes (n) |
| Zygote | the diploid product of the union of haploid gametes during fertilization; a fertilized egg |
| Fertilization | the union of haploid gametes to produce a diploid zygote |
| Meiosis | a modified type of cell division in sexually reproducing organisims consisting of two rounds of cell division but only one round of DNA replication, it results in cells with half the number of chromosome sets as the original cell |
| Meiosis I | (separation of homologous chromosomes) the first division of a two-stage process of cell division in sexually reproducing organsims that results in haploid cells with replicated chromosomes |
| Meiosis II | (separation of sister chromatids) the second division of a two-stage process of cell division in sexually reproducing organisms that results in haploid cells with unreplicated chromosomes |
| Nonsister Chromatids | different chromatids (maternal and paternal) of the same chromosome |
| Prophase I | chromosomes begin to condense, crossing over is completed while the homologs are in synapsis, each homologous pair has one ore more chiasmata, points where crossing over has occured and the homologs are still associated due to cohesion between sister chromatids, centrosome movement, spindle formation, and nuclear envelope breakdown occur, microtubules from one pole or the other attach to the kinetochores |
| Metaphase I | pairs of homologous chromosomes are now arranged on the metaphase plate, with one chromosome in each pair facing each pole, both chromatids of one homolog are attached to kinetochore microtubles from one pole; those of the other homolog are attached to microtubles from the opposite pole |
| Anaphase I | breakdown of protein responsible for sister chromatid cohesion along chromatid arms allows homologs to separate, the homologs move towards opposite poles, guided by the spindle apparatus, sister chromatid cohesion persists at the centromere, causing chromatids to move as the unit move towards the same pole |
| Telophase I and Cytokinesis | at the beginning of telophase I, each half of the cell has a complete haploid set of replicated chromosomes, each chromosome is composed of two sister chromatids; one or both chromatids include regions of nonsister chromatid DNA, cytokinesis usually occurs simultaneously with telophase 1 forming two haploid daughter cells, in animal cells, a cleavage furrow forms (in plant cells a cell plate forms), in some species, chromosome decondense and the nuclear envelope re-forms |
| Prophase II | a spindle apparatus forms, in late stage, chromosomes (each still composed of two chromatids associated at the centromere) move towards the metaphase II plate |
| Metaphase II | the chromosomes are posistioned on the metaphase plate as in mitosis, because of crossing over in meiosis I, the two sister chromatids of each chromosome are not genetically identical, the kinetochores of sister chromatids are attached to microtubules extending from opposite poles |
| Anaphase II | breakdown of proteins holding the sister chromatids together at the centromere allows the chromatids to separate, the chromatids move toward opposite poles as individual chromosomes |
| Telophase II and Cytokinesis | nuclei form, the chromosomes begin decondensing, and cytokinesis occurs, the meiotic division of one parent cell produces four daughter cells, each with a haploid set of unreplicated chromosomes, each of the four daughter cells is genetically distinct from the other daughter cells and from the parent cell |
| Events Unique to Meiosis | synapsis and crossing over(meiosis I), homologs on the metaphase plate(meiosis I), separation of homologs (meiosis I) |
| Synapsis | the pairing and physical connection of replicated homologous chromosomes during prophase I of meiosis |
| Chiasma | (plural chiasmata) the X-shaped, microscopically visible region where homologous nonsister chromatids have exchanged genetic material through crossing over duing meiosis, the two homologs remaining associated due to sister chromatid cohesion |
| Crossing Over | the reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis |
| Recombinant Chromosomes | a chromosome created when crossing over combines the DNA from two parents into a single chromosome |
| Independent Assortment | because each homologous pair of chromosomes is positioned independently of the other pairs at metaphase I, the first meiotic division results in each pair sorting its maternal and paternal homologs into daughter cells independently of every other pair |
| Meiosis and Diversity | crossing over (nonsister chromatids), alternative arrangements (homologous chromosomes), random fertilization, mutational contributions |
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