Cell Bio Campbell Chapter 12 Mitosis

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Gametes

Back 1

½ the number of chromosomes

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Somatic cells

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All non reproductive cells

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Chromatin

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DNA not condensed in the nucleus

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None

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Centromere

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Tthe region where sister chromatids join in the double chromosomal structure during mitosis, prophase and metaphase. Also where kinetochore formation takes place: proteins bind here that form an anchor point for the spindle formation required for the pull of chromosomes toward the centrioles during the anaphase and telophase of mitosis. Aberrant formation can lead to improper chromosomal alignment and segregation, resulting in aneuploidy and conditions such as Down syndrome.

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Front 5

Mitosis

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Mitosis is the process in which a cell duplicates its chromosomes to generate two, identical cells. It is generally followed by cytokinesis which divides the cytoplasm and cell membrane. This results in two identical cells with an equal distribution of organelles and other cellular components. Mitosis and cytokinesis jointly define the mitotic (M) phase of the cell cycle

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Meiosis

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the process by which one diploid eukaryotic cell divides to generate four haploid cells often called gametes.

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Interphase

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Defined only by the absence of cell division. The cell obtains nutrients, and duplicates its chromatids. There are 3 parts : G1 (growth 1 in which the cell creates organelles and begins metabolism), S phase (DNA synthesis in which the chromosomes of the cell are copied) and G2 (growth 2 in which the cell grows in preparation for cell division).

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Front 8

Prophase

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chromatin condenses into a highly ordered structure called a chromosome

Front 9

Prometaphase

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early prometaphase, the nuclear membrane has just degraded, allowing the microtubules to quickly interact with the kinetochores on the chromosomes, which have just condensed.

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Metaphase

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Microtubules formed in prophase have already found and attached themselves to kinetochores. The centromeres of the chromosomes convene themselves on the _____ plate

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None

Front 11

Anaphase

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early anaphase (or Anaphase A) the chromatids abruptly separate and move towards the spindle poles. This is achieved by shortening of the spindle microtubules, and forces are mainly exerted at the kinetochores. When the chromatids are fully separated late anaphase (or Anaphase B) begins. This involves the polar microtubules elongating and sliding relative to each other to drive the spindle poles further apart.

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Kinetochore

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Protein structure in eukaryotes which assembles on the centromere and links the chromosome to microtubule polymers from the mitotic spindle during mitosis and meiosis. Contains two regions: an inner _____, which is tightly associated with the centromere DNA; and an outer ______, which interacts with microtubules.

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None

Front 14

Centrosome

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Composed of two orthogonally arranged centrioles surrounded by an amorphous mass of pericentriolar material (PCM). The PCM contains proteins responsible for microtubule nucleation and anchoring including γ-tubulin, pericentrin and ninein. Each centriole comprises nine triplet microtubule blades in a pinwheel structure as well as centrin, cenexin and tektin

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Front 15

Telophase

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At this stage, the non-kinetochore microtubules continue to lengthen, further elongating the cell. Corresponding sister chromosomes, which are the results of anaphase, attach at opposite ends of the cell. A new nuclear envelope, using fragments of the parent cell's nuclear membrane, forms around each set of separated sister chromosomes. Both sets of chromosomes, now surrounded by new nuclei, unfold back into chromatin.

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Mitotic spindle

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Function is to segregate chromosomes during cell division (either mitosis or meiosis) to the daughter cells. It consists of a bundle of microtubules joined at the ends but spread out in the middle, vaguely ellipsoid in shape. In the wide middle portion, known as the spindle midzone, antiparallel microtubules are bundled by kinesins. At the pointed ends, known as spindle poles, microtubules are nucleated by the centrosomes.

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Front 17

Cleavage furrow

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First sign of cytokinesis, it is a shallow groove in the cell.

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Cell plate formation

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Delivery of Golgi-derived vesicles carrying cell wall components to the plane of cell division and the subsequent fusion of these vesicles within this plane. Is the final stage of cytokinesis in terrestrial plants.

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Front 19

Binary fission

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form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size, used by most prokaryotes. This process results in the reproduction of a living cell by division into two equal or near-equal parts. DNA replication starts from an origin of replication, which opens up into a replication bubble. The replication bubble separates the DNA double strand, each strand acts as template for synthesis of a daughter strand by semiconservative replication, until the entire prokayotic DNA is duplicated. Each circular DNA strand then attaches to the cell membrane, sometimes by a mesosome. The cell elongates, causing the two chromosomes to separate.Cell division in bacteria is controlled by the septal ring, a collection of about a dozen proteins that collect around the site of division. There, they direct assembly of the division septum. The cell membrane then invaginates (grows inwards) and splits the cell into two daughter cells, separated by a newly grown cell plate. This process is called cytokinesis.

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Cell cycle control system

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Cyclically operating set of molecules in the cell that both triggers and coordinates key events in the cell cycle.

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Cell cycle checkpoints

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Where a stop and go signal can regulate the cell cycle. The 3 major check-points are found at G1, G2, and M phases.

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G1

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period in the cell cycle during interphase, after cytokinesis and before the S phase. For many cells, this phase is the major period of cell growth during its lifespan. During this stage new organelles are being synthesized, so the cell requires both structural proteins and enzymes, resulting in great amount of protein synthesis. The metabolic rate of the cell will be high. Consists of four subphases:
1. Competence (g1a)
2. Entry (g1b)
3. Progression (g1c)
4. Assembly (g1d)

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G2

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the third, final, and usually the shortest subphase during interphase within the cell cycle in which the cell undergoes a period of rapid growth to prepare for mitosis. It follows successful completion of DNA synthesis and chromosomal replication during the S phase, and occurs during a period of often four to five hours. This far into interphase the nucleus is well defined, bound by a nuclear envelope and contains at least one nucleolus. Although chromosomes have been replicated they cannot yet be distinguished individually because they are still in the form of loosely packed chromatin fibers. The G2 phase prepares the cell for mitosis (M phase) which is initiated by prophase.

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Cyclin

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A family of proteins involved in the progression of cells through the cell cycle. So named because their concentration varies in a cyclical fashion during the cell cycle; they are produced or degraded as needed in order to drive the cell through the different stages of the cell cycle.

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Cyclin dependent kinase (CDKs)

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group of protein kinases originally discovered as being involved in the regulation of the cell cycle. A cyclin-dependent kinase is activated by association with a cyclin forming a cyclin-dependent kinase complex.

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Growth factor

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Protein released by certain body cells to stimulate other cells to divide.

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None

Front 27

Density dependent inhibition

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A phenomenon where crowded cells stop dividing.

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Anchorage dependence

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In order to divide the cells must be attached to a substratum.

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Transformation

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Process by which converts a normal cell to a cancerous cell.

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Tumor

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Mass of abnormal cells

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Benign tumor

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Abnormal cells that remain at the original site

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Malignant tumor

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Invasive enough to affect the function of one or more organs

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Metastasis

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Spread of cancer cells to locations distant to the original site.