Cell Division & Reproduction; The Eukaryotic Cell Cycle and Mitosis; Meiosis and Crossing Over; Alterations of Chromosome Number and Structure.
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| 214373453 | cell division | The reproduction of a cell through duplication of the genome and division of the cytoplasm. | |
| 214373454 | chromosome | A threadlike, gene-carrying structure found in the nucleus of a eukaryotic cell and most visible during mitosis and meiosis; also, the main gene-carrying structure of a prokaryotic cell. A chromosomes consists of one very long piece of chromatin, a combination of DNA and protein. | |
| 214373455 | asexual reproduction | The creation of genetically identical offspring by a single parent, without the participation of sperm and egg. | |
| 214373456 | sexual reproduction | The creation of genetically unique offspring by the fusion of two haploid sex cells (gametes), forming a diploid zygote. | |
| 214373457 | binary fission | A means of asexual reproduction in which a parent organism, often a single cell, divides into two genetically identical individuals of about equal size. **prokaryotic cells | |
| 214373458 | Binary Fission Process | 1. As the chromosome is duplicating, the copies move towards the opposite ends of the cell. 2. The cell elongates 3. When the chromosome duplication is complete and the cell has reached about twice its initial size, the plasma membrane grows inward and more cell wall is made, dividing the parent cell into two daughter cells | |
| 214373459 | chromatin | The combination of DNA and proteins that constitutes eukaryotic chromosomes; often used to refer to the diffuse, very extended form taken by chromosomes when a cell is not dividing. | |
| 214373460 | sister chromatid | One of the two identical parts of a duplicated chromosome in a eukaryotic cell. Prior to mitosis, sister chromatids remain attached to each another at the centromere. | |
| 214373461 | centromere | The region of a duplicated chromosome where two sister chromatids are joined (often appearing as a narrow "waist") and where spindle microtubules attach during mitosis and meiosis. The centromere divides at the onset of anaphase during mitosis and anaphase II during meiosis. | |
| 214373462 | cell cycle | An ordered sequence of events (including interphase and the mitotic phase) that extends from the time a eukaryotic cell is first formed from a dividing parent cell until its own division into two cells. | |
| 214373463 | interphase | The period in the eukaryotic cell cycle when the cell is not actually dividing. Constitutes for 90% of the cell cycle. Consists of G1 (First growing Gap), The S phase (Synthesis: Chromosomes duplicate during this period), and G2 (Second growing Gap). | |
| 214373464 | mitotic phase | The part of the cell cycle when the nucleus divides (via mitosis), its chromosomes are distributed to the daughter nuclei, and the cytoplasm divides (via cytokinesis), producing two daughter cells. Only 10% of Cell Cycle. Divided into Mitosis and Cytokinesis. | |
| 214373465 | mitosis | The division of a single nucleus into two genetically identical nuclei. | |
| 214373466 | cytokinesis | The division of the cytoplasm to form two separate daughter cells. Cytokinesis usually occurs in conjunction with telophase of mitosis. The division of the the cytoplasm. In animal cells, a cleavage furrow forms, and the cell pinches into two. | |
| 214373467 | How many human chromosomes are there? | 46 | |
| 214373468 | prophase | The first stage of mitosis, during which the chromatin condenses to form structures (sister chromatids) visible with a light microscope and the mitotic spindle begins to form, but the nucleus is still intact. | |
| 214373469 | prometaphase | The second stage of mitosis, during which the nuclear envelope fragments and the spindle microtubules attach to the protein structures, called "kinetochore," of the sister chromatids. This throws the chromosome into agitated motion. Other microtubules come in contact with microtubules from the opposite poles. Forces made by protein motors move the chromosomes towards the center of the cell. | |
| 214373470 | metaphase | The third stage of mitosis, during which all the cell's duplicated chromosomes are lined up at an imaginary plane equidistant between the poles of the mitotic spindle. Mitotic spindle is fully formed. The chromosome's centromeres line up on the "metaphase plate." | |
| 214373471 | anaphase | The fourth stage of mitosis, beginning when sister chromatids separate from each other and ending when a complete set of daughter chromosomes arrives at each of the two poles of the cell. Motor Proteins of the kinetochores, powered by ATP, "walk" the daughter chromosomes centromere-first along the microtubules toward the opposite poles of the cell. The spindle microtubules shorten, however, the microtubules not attached to chromosomes start to lengthen and the poles are moved father apart, elongating the cell. | |
| 214373472 | telophase | The fifth and final stage of mitosis, during which daughter nuclei form at the two poles of a cell. Telophase usually occurs together with cytokinesis. Cell elongation, started in anaphase, continues. Nuclear envelopes form around the chromosomes. Telophase is basically the reverse of propahse. The chromatin fiber of each chromosome uncoils, and the mitotic spindle disappears. This fully concludes Mitosis. | |
| 214373473 | mitotic spindle | A football-shaped structure formed of microtubules and associated proteins that is involved in the movement of chromosomes during mitosis and meiosis. | |
| 214373474 | centrosome | Material in the cytoplasm of a eukaryotic cell that gives rise to microtubules; important in mitosis and meiosis; also called the microtubule-organizing center. | |
| 214373475 | cleavage furrow | The first sign of cytokinesis during cell division in an animal cell; a shallow groove in the cell surface near the old metaphase plate. The cytoplasm has a ring of microfilaments made of actin. (along with myosin, is responsible for cell contraction.) This microfilament reacts with myosin and contracts until the cell pinches in two. | |
| 214373476 | Plant Cytokinesis | During telophase, membranous vesicles containing cell wall material collect at the middle of the parent cell. The vesicles fuse forming a membranous disk call the cell plate. The cell plate grows outward, accumulating more cell wall material as more vesicles fuse with it. Eventually, the membrane of the cell plate fuses with the plasma membrane, and the cell plate's contents join with the parental cell wall. | |
| 214373477 | cell plate | A double membrane across the midline of a dividing plant cell, between which the new cell wall forms during cytokinesis. | |
| 220050481 | growth factor | A protein secreted by certain body cells that stimulates other cells to divide. (50) VEGF works as anticancer | |
| 220050482 | density-dependent inhibition | The ceasing of cell division that occurs when cells touch one another. (Cancer cells fail to exhibit this trait) | |
| 220050483 | anchorage dependence | The requirement that to divide, a cell must be attached to a solid surface. | |
| 220050484 | cell cycle control system | A cyclically operating set of proteins that triggers and coordinates events in the eukaryotic cell cycle. | |
| 220050485 | Tumor | An abnormal mass of rapidly growing cells that forms within otherwise normal tissue. | |
| 220050486 | Benign Tumor | An abnormal mass of cells that remains at its original site in the body. | |
| 220050487 | Malignant Tumor | An abnormal tissue mass that can spread into neighboring tissue and to other parts of the body; a cancerous tumor. | |
| 220050488 | Cancer | A disease characterized by the presence of malignant tumors (rapidly growing and spreading masses of abnormal body cells) in the body. | |
| 220050489 | Metastasis | The spread of cancer cells beyond their original site. | |
| 220050490 | Carcinoma | Cancer that originates in the coverings of the body, such as skin or the lining of the intestinal tract. | |
| 220050491 | Sarcoma | Cancer of the supportive tissues, such as bone, cartilage, and muscle. | |
| 220050492 | 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 them in the blood; cancer of the bone marrow cells that produce leukocytes. | |
| 220050493 | Lymphoma | Cancer of the tissues that form white blood cells. | |
| 220050494 | Somatic Cell | Any cell in a multicellular organism except a sperm or egg cell or a cell that develops into a sperm or egg. | |
| 220050495 | Homologous Chromosomes | The two chromosomes that make up a matched pair in a diploid cell. Homologous chromosomes are of the same length, centromere position, and staining pattern and possess genes for the same characteristics at corresponding loci. One homologous chromosome is inherited from the organism's father, the other from the mother. | |
| 220050496 | Locus | The particular site where a gene is found on a chromosome. Homologous chromosomes have corresponding gene loci. | |
| 220050497 | Sex Chromosomes | A chromosome that determines whether an individual is male or female. | |
| 220050498 | Autosome | A chromosome not directly involved in determining the sex of an organism; in mammals, for example, any chromosome other than X or Y. | |
| 220050499 | 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. | |
| 220050500 | Diploid | In an organism that reproduces sexually, a cell containing two homologous sets of chromosomes, one set inherited from each parent; a 2n cell. | |
| 220050501 | Gamete | A sex cell; a haploid egg or sperm. The union of two gametes of opposite sex (fertilization) produces a zygote. | |
| 220050502 | Haploid | In the life cycle of an organism that reproduces sexually, a cell containing a single set of chromosomes; an n cell. | |
| 220050503 | Fertilization | The union of the nucleus of a sperm cell with the nucleus of an egg cell, producing a zygote. | |
| 220050504 | Zygote | The diploid fertilized egg, which results from the union of a sperm cell nucleus and an egg cell nucleus. | |
| 220050505 | Tetrad | A paired set of homologous chromosomes, each composed of two sister chromatids. Tetrads form during prophase I of meiosis, when crossing over may occur. | |
| 220050506 | Crossing Over | The exchange of segments between chromatids of homologous chromosomes during synapsis in prophase I of meiosis; also, the exchange of segments between DNA molecules in prokaryotes. | |
| 220050507 | Chiasma | The microscopically visible site where crossing over has occurred between chromatids of homologous chromosomes during prophase I of meiosis. | |
| 220050508 | Nonsister chromatids break at the same place | 1st step in homologous chromosomes | |
| 220050509 | Broken chromatids join together with opposite chromatids | 2nd step in homologous chromosomes | |
| 220050510 | After anaphase 1, each contains a new segment originating from its homolog | 3rd step in homologous chromosomes | |
| 220050511 | In Meiosis 2, gametes separate, each going to a different gamete | 4th step in homologous chromosomes | |
| 220050512 | genetic recombination | The production, by crossing over and/or independent assortment of chromosomes during meiosis, of offspring with allele combinations different from those in the parents. The term may also be used more specifically to mean the production by crossing over of eukaryotic or prokaryotic chromosomes with gene combinations different from those in the original chromosomes. | |
| 220050513 | karyotype | A display of micrographs of the metaphase chromosomes of a cell, arranged by size and centromere position. Karyotypes may be used to identify certain chromosomal abnormalities. | |
| 220050514 | Down syndrome | A human genetic disorder resulting from the presence of an extra chromosome 21; characterized by heart and respiratory defects and varying degrees of mental retardation. | |
| 220050515 | nondisjunction | An accident of meiosis or mitosis in which a pair of homologous chromosomes or a pair of sister chromatids fail to separate at anaphase. | |
| 220050516 | deletion | The loss of one or more nucleotides from a gene by mutation; the loss of a fragment of a chromosome. | |
| 220050517 | duplication | Repetition of part of a chromosome resulting from fusion with a fragment from a homologous chromosome; can result from an error in meiosis or from mutagenesis. | |
| 220050518 | inversion | A change in a chromosome resulting from reattachment of a chromosome fragment to the original chromosome, but in a reverse direction. Mutagens and errors during meiosis can cause inversions. | |
| 220050519 | translocation | (1) During protein synthesis, the movement of a tRNA molecule carrying a growing polypeptide chain from the A site to the P site on a ribosome. (The mRNA travels with it.) (2) A change in a chromosome resulting from a chromosomal fragment attaching to a nonhomologous chromosome; can occur as a result of an error in meiosis or from mutagenesis. |
