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Biology 2 AP
Chapter 12
45
Biology
11th Grade
01/17/2009

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Term
Cell Division
Definition
The reproduction of cells.
Term
Cell Cycle
Definition
An ordered sequence of events in the life of a eukaryotic cell, from its origin in the division of a parent cell until its own division into two; composed of the M, G1, S, and G2 phases.
Term
Genome
Definition
The complete complement of an organism’s genes; an organism’s genetic material.
Term
Chromosomes
Definition
A threadlike, gene-carrying structure found in the nucleus. Each chromosome consists of one very long DNA molecule and associated proteins. See chromatin.
Term
Somatic Cells
Definition
Any cell in a multicellular organism except a sperm or egg cell.
Term
Gametes
Definition
A haploid cell, such as an egg or sperm. Gametes unite during sexual reproduction to produce a diploid zygote.
Term
Chromatin
Definition
The complex of DNA and proteins that makes up a eukaryotic chromosome. When the cell is not dividing, chromatin exists as a mass of very long, thin fibers that are not visible with a light microscope.
Term
Sister Chromatids
Definition
Replicated forms of a chromosome joined together by the centromere and eventually separated during mitosis or meiosis II.
Term
Centromere
Definition
The centralized region joining two sister chromatids.
Term
Mitosis
Definition
A process of nuclear division in eukaryotic cells conventionally divided into five stages: prophase, prometaphase, metaphase, anaphase, and telophase. Mitosis conserves chromosome number by equally allocating replicated chromosomes to each of the daughter nuclei.
Term
Cytokinesis
Definition
The division of the cytoplasm to form two separate daughter cells immediately after mitosis.
Term
Meiosis
Definition
A two-stage type of cell division in sexually reproducing organisms that results in cells with half the chromosome number of the original cell.
Term
Mitotic (M) Phase
Definition
The phase of the cell cycle that includes mitosis and cytokinesis.
Term
Interphase
Definition
The period in the cell cycle when the cell is not dividing. During interphase, cellular metabolic activity is high, chromosomes and organelles are duplicated, and cell size may increase. Interphase accounts for 90% of the cell cycle.
Term
G1 Phase
Definition
The first growth phase of the cell cycle, consisting of the portion of interphase before DNA synthesis begins.
Term
S Phase
Definition
The synthesis phase of the cell cycle; the portion of interphase during which DNA is replicated.
Term
G2 Phase
Definition
The second growth phase of the cell cycle, consisting of the portion of interphase after DNA synthesis occurs.
Term
Prophase
Definition
The first stage of mitosis, in which the chromatin is condensing and the mitotic spindle begins to form, but the nucleolus and nucleus are still intact.
Term
Prometaphase
Definition
The second stage of mitosis, in which discrete chromosomes consisting of identical sister chromatids appear, the nuclear envelope fragments, and the spindle microtubules attach to the kinetochores of the chromosomes.
Term
Metaphase
Definition
The third stage of mitosis, in which the spindle is complete and the chromosomes, attached to microtubules at their kinetochores, are all aligned at the metaphase plate.
Term
Anaphase
Definition
The fourth stage of mitosis, in which the chromatids of each chromosome have separated and the daughter chromosomes are moving to the poles of the cell.
Term
Telophase
Definition
The fifth and final stage of mitosis, in which daughter nuclei are forming and cytokinesis has typically begun.
Term
Mitotic Spindle
Definition
An assemblage of microtubules and associated proteins that is involved in the movements of chromosomes during mitosis.
Term
Centrosome
Definition
Material present in the cytoplasm of all eukaryotic cells, important during cell division; the microtubule-organizing center.
Term
Aster
Definition
A radial array of short microtubules that extends from each centrosome toward the plasma membrane in a cell undergoing mitosis.
Term
Kinetochore
Definition
A specialized region on the centromere that links each sister chromatid to the mitotic spindle.
Term
Metaphase Plate
Definition
An imaginary plane during metaphase in which the centromeres of all the duplicated chromosomes are located midway between the two poles.
Term
Cleavage
Definition
The process of cytokinesis in animal cells, characterized by pinching of the plasma membrane. Also, the succession of rapid cell divisions without growth during early embryonic development that converts the zygote into a ball of cells.
Term
Cleavage Furrow
Definition
The first sign of cleavage in an animal cell; a shallow groove in the cell surface near the old metaphase plate.
Term
Cell Plate
Definition
A double membrane across the midline of a dividing plant cell, between which the new cell wall forms during cytokinesis.
Term
Binary Fission
Definition
The type of cell division by which prokaryotes reproduce. Each dividing daughter cell receives a copy of the single parental chromosome.
Term
Origin of Replication
Definition
Site where the replication of a DNA molecule begins.
Term
Cell Cycle Control System
Definition
A cyclically operating set of molecules in the cell that triggers and coordinates key events in the cell cycle.
Term
Checkpoint
Definition
A critical control point in the cell cycle where stop and go-ahead signals can regulate the cycle.
Term
G0 Phase
Definition
A nondividing state in which a cell has left the cell cycle.
Term
Cyclin
Definition
A regulatory protein whose concentration fluctuates cyclically.
Term
Cyclin-Dependent Kinases (CDKS)
Definition
A protein kinase that is active only when attached to a particular cyclin.
Term
MPF
Definition
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.
Term
Growth Factor
Definition
A protein that must be present in the extracellular environment (culture medium or animal body) for the growth and normal development of certain types of cells; a local regulator that acts on nearby cells to stimulate cell proliferation and differentiation.
Term
Density-Dependent Inhibition
Definition
The phenomenon observed in normal animal cells that causes them to stop dividing when they come into contact with one another.
Term
Anchorage Dependence
Definition
The requirement that to divide, a cell must be attached to the substratum.
Term
Transformation
Definition
(1) The conversion of a normal animal cell to a cancerous cell. (2) A change in genotype and phenotype due to the assimilation of external DNA by a cell.
Term
Benign Tumor
Definition
A mass of abnormal cells that remains at the site of origin.
Term
Malignant Tumor
Definition
A cancerous tumor that is invasive enough to impair the functions of one or more organs.
Term
Metastasis
Definition
The spread of cancer cells to locations distant from their original site.
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