| 5140416036 | Cell Division | - The reproduction of cells.
- The continuity of life is based on this.
- The division of one prokaryotic cell reproduces an entire organism (same with a unicellular eukaryote).
- Cell division enables multicellular eukaryotes to develop from a single cell, and then later functions in renewal and repair of cells. | | 0 |
| 5140416037 | Cell Cycle | - The life of a cell from the time it is first formed from a dividing parent cell until its own division into two daughter cells. | | 1 |
| 5140416038 | Genome | - A genome is a cells endowment of DNA (genetic information).
- A prokaryotic genome is often a single DNA molecule and eukaryotic genomes usually consist of a number of DNA molecules.
- Before a cell can divide to form genetically identical daughter cells, all of this DNA must be copied, and then the two copies must be separated so that each daughter cell ends up with a complete genome. | | 2 |
| 5140416039 | Chromosomes | - DNA is packaged into these structures.
- Each eukaryotic chromosome has a long linear DNA molecule associated with many proteins which maintain the structure of the chromosome and help control the activity of the genes. | | 3 |
| 5140416040 | Chromatin | - The entire complex of DNA and proteins that is the building material of chromosomes. | | 4 |
| 5140416041 | Somatic cells | - All body cells except the reproductive cells.
- The nuclei of human somatic cells each contain 46 chromosomes, made up of 2 sets of 23 (one set inherited from each parent).
- The # of these cells in other species varies. | | 5 |
| 5140416042 | Gametes | - Reproductive cells (sperm and eggs)
- These cells have one set of 23 chromosomes in humans. | | 6 |
| 5140416043 | Sister Chromatids | - Joined copies of an original chromosome.
- After DNA has been replicated each chromosome has 2 of these.
- The 2 chromatids are initially attached by protein complexes called chohesins (this attachment is called sister chromatid cohesion). |  | 7 |
| 5140416044 | Centromere | - Each sister chromatid has one of these
- A centromere is a region that contains specific DNA sequences where the chromatid is attached most closely to its sister chromatid.
- The part of a chromatid on either side of the centromere is referred to as an arm of the chromatid. | | 8 |
| 5140416045 | Chromosome duplication and distribution during cell division | 1. Before a chromosome is duplicated it is normally a long thin chromatin fiber containing one DNA molecule and associated proteins.
2. Once duplicated, a chromosome consists of 2 sister chromatids connected by sister chromatid cohesion. Each chromatid contains a copy of the DNA molecule.
3. Molecular and mechanical processes separate the sister chromatids into 2 chromosomes and distribute them to two daughter cells. |  | 9 |
| 5140416046 | Mitosis | - The division of the genetic material in the nucleus usually followed immediately by cytokinesis. | | 10 |
| 5140416047 | Cytokinesis | - The division of the cytoplasm. | | 11 |
| 5140416048 | Chromosome number (human life cycle) | - ou inherit 46 chromosomes 23 from each parent which are combine din the nucleus of a cell when a sperm unites with an egg forming a zygote (fertilized egg).
- The same process then continues to generate new cells to replace dead and damaged somatic cells. | | 12 |
| 5140416049 | Meiosis | - A variation of cell division that produces gametes (eggs or sperm) and creates nonidentical daughter cells that only have on set of chromosomes.
- Occurs only in the gonads (ovaries or testes)
- Reduces the chromosome number from 46 (2 sets) to 23 (1 set).
- Fertilization fuses 2 gametes together and returns the chromosome number to 46 and mitosis conserves that number in every somatic cell nucleus of the new individual. | | 13 |
| 5140416050 | Mitotic phase | - Phase of the cell cycle that includes both mitosis and cytokinesis (usually the shortest phase).
- This alternates with a longer stage, interphase.
- Mitosis is broken down into 5 stages: prophase, pro metaphase, metaphase, anaphase and telophase.
- It then overlaps with cytokinesis completing the mitotic phase. | | 14 |
| 5140416051 | Interphase | - Accounts for about 90% of the cycle.
- This divided into sub phases: G1 phase ("first gap"), the S phase ("synthesis") and the G2 phase ("second gap").
- During these sub phases, a cell grows by producing proteins and cytoplasmic organelles.
- Chromosomes are duplicated only during the S phase.
- A cell grows (G1), continues to grow as it copies its chromosomes (S), grows more as it completes preparations for cell division (G2) and divides (M). | | 15 |
| 5140416052 | Mitotic spindle | - Many events in mitosis depend on this structure which begins to for in the cytoplasm during prophase.
- Consists of fibers made of microtubules and associated proteins.
- Mitotic spindle assembles by using material (microtubules) from the cytoskeleton which partially disassembles. | | 16 |
| 5140416053 | Centrosome | - A subcellular region containing material that functions throughout the cell cycle to organize the cell's microtubules.
- Centrioles are located at the center of the centrosome but they are not essential since, if they are destroyed, a spindle fiber still forms during mitosis. | | 17 |
| 5140416054 | Aster | - A radial array of short microtubules that extends from each centrosome. | | 18 |
| 5140416055 | Kinetochore | - A structure made up of proteins that have assembled on specific sections of chromosomal DNA at each centromere.
- Each of the 2 sister chromatids of duplicated chromosome has a kinetochore.
- During pro metaphase some spindle microtubules attach to kinetochores forming kinetochore microtubules. | | 19 |
| 5140416056 | Metaphase plate | - A region where the centromeres of all the duplicated chromosomes lie between the spindle's two poles in metaphase. | | 20 |
| 5140416057 | Separase | - The enzyme that cleaves sister chromatids of each chromosome during anaphase.
- Once separated the chromatids become chromosomes. | | 21 |
| 5140416058 | Motor Proteins | - In anaphase, motor proteins might walk the chromosomes along the microtubules which depolymerize at their kinetochore ends after the motor proteins have passed. ("paceman" mechanism)
- Other researches have proposed that chromosomes re "reeled in" by motor proteins at the spindle poles and that the microtubules depolymerize after they pass by these motor proteins.
- Its widely agreed that both mechanisms are used. | | 22 |
| 5140416059 | Cleavage | - In animal cells, cytokinesis occurs by this process. |  | 23 |
| 5140416060 | Cleavage furrow | - A shallow groove in the cell surface near the old metaphase plate.
- A contractile ring of actin microfilaments on the cytoplasmic side of the furrow interact with myosin molecules causing the ring to contract.
- This causes the cleavage furrow to deepen until the parent cell is pinched in two cells. | | 24 |
| 5140416061 | Cell plate | - A structure formed in plant cells.
- During telophase, vesicles derived from the Golgi apparatus move along microtubules to the middle cells where they coalesce and produce this structure.
- The cell plate enlarges until its surrounding membrane fuses with the plasma membrane along the perimeter of the cell producing two daughter cells. |  | 25 |
| 5140416062 | Binary fission | - The process where prokaryotes (bacteria and archaea) reproduce and single-celled eukaryotes reproduce asexually.
- The process in eukaryotes involves mitosis, while the process in prokaryotes does not. | | 26 |
| 5140416063 | Origin of replication | - A specific place on a chromosome.
- By studying origins of replications have found that the two origins of replication end up at opposite ends of the cell or in some other specific location.
- Scientists are still unsure of how bacterial chromosomes move and how their specific location is established. | | 27 |
| 5140416064 | E. Coli Replication | - In E. coli the process of cell division is initiated when the DNA of the bacterial chromosomes begins to replicate at the origin of replication.
- One origin moves toward the opposite end of the cell as the chromosome replicates.
- When the replication is complete, and the bacterium is twice its initial size, the plasma membrane pinches dividing the E. coli into 2 daughter cells. | | 28 |
| 5140416065 | Evolution of Mitosis | - We can hypothesize that mitosis evolved from simpler prokaryotic cell reproduction since some proteins involved in bacterial binary fission are similar to eukaryotic proteins in mitosis.
- Possible intermediate stages in the evolution of mitosis might be found in dinoflagellates, diatoms and some yeasts.
- In these types of nuclear division, the nuclear envelope remains intact in contrast to what happens in most eukaryotic cells. | | 29 |
| 5140416066 | Dinoflagellates | - In these unicellular eukaryotes, chromosomes attach to the nuclear envelope, which remains intact during cell division.
- Microtubules pass through the nucleus inside cytoplasmic tunnels, reinforcing the spatial orientation of the nucleus, which then divides in a process similar to bacterial binary fission. |  | 30 |
| 5140416067 | Diatoms & some yeasts | - The nuclear envelope maintains intact during cell division.
- The microtubules from a spindle within the nucleus and separate the chromosomes.
- The nucleus then splits into two daughter nuclei. |  | 31 |
| 5140416068 | Regulation of the Eukaryotic Cell cycle | - Different cells divide at different rates.
- Human skin cells divide frequently throughout life, while liver cells maintain the ability to divide but keep it in reserve until an appropriate need arises | | 32 |
| 5140416069 | Evidence for Cytoplasmic Signals | - Evidence for the hypothesis that the cell cycle is driven by specific signaling molecules present in the cytoplasm came from experiments with mammalian cells grown in culture.
- 2 cells in different phases of the cell cycle were fused to form a single cell with 2 nuclei.
- If one was in the S phase and the other was in G1, the G1 nucleus immediately entered the S phase (as if it was stimulated by singling molecules present in the cytoplasm of the first cell). | | 33 |
| 5140416070 | Cel cycle Control System | - A cyclically operating set of molecules in the cell that both triggers and coordinates key events in the cell cycle.
- It proceeds on its own but is regulated at certain checkpoints by both internal and external signals.
- Cell cycle is regulated by a set of regulatory proteins and protein complexes including kinases and cyclins. | | 34 |
| 5140416071 | Checkpoint | - A control point where stop and go-ahead signals can regulate the cycle.
- Transmitted within the cell by signal transduction pathways.
- These signals report whether crucial cellular processes that should have occurred by that point have been completed correctly and thus wether or not the cell cycle should proceed.
- Three major checkpoints are found in the G1, G2 and M phases. | | 35 |
| 5140416072 | G0 phase | - If the checkpoint at the G1 phase does not receive a go-ahead signal a cell will exit the cycle and switch to the G0 phase.
- Most cells of the human body are actually in this phase such as mature nerve cells and muscle cells. | | 36 |
| 5140416073 | M phase checkpoint | - Anaphase does not begin until all the chromosomes are properly attached to the spindle at the metaphase plate.
- As long as some kinetochores are unattached to spindle microtubules, the sister chromatids remain together and delay anaphase.
- The appropriate regulatory protein complex only becomes activated when kinetochores of all the chromosomes are properly attached to the spindle.
- Once activated, the complex activates the enzyme separase which separates sister chromatids.
- This ensures that daughter cells have the correct number of chromosomes.
- This is an internal signal that regulates the cell cycle. | | 37 |
| 5140416074 | Growth Factor | - A protein release by certain cells that stimulates other cells to divide.
- Most types of mammalian cells divide in culture only if the growth medium includes specific growth factors.
- This is an example of an external signal that regulates the cycle cycle. | | 38 |
| 5140416075 | Platelet-Derived Growth Factors (PDGF) | - Made by blood cell fragments called platelets.
- Required for the division of cultured fibroblasts (connective tissue cell).
- When PDGF binds to PDGF receptors on fibroblast membranes, a signal transduction pathway is triggered that allows the cells to pass the G1 checkpoint and divide.
- When an injury occurs in an anima's body, platelets release PDGF in the vicinity and the proliferation of fibroblasts helps heal the wound. |  | 39 |
| 5140416076 | Density-Dependent Inhibition | - A phenomenon in which crowded cells stop dividing.
- Cultured cells normally divide until they form a single layer of cells on the inner surface of a culture container and stop dividing.
- If cells are removed, other cells divide until the space is filled.
- The binding of a cell-surface protein to its counterpart on an adjoining cell sends a cell division-inhibiting signal to both cells which stops them from continuing the cell cycle. | | 40 |
| 5140416077 | Anchorage dependance | - Most cells must attach to external surface before they can divide.
- Studies suggest that anchorage is signaled to the cell control system via pathways involving plasma membrane proteins and elements of the cytoskeleton linked to them. | | 41 |
| 5140416078 | Cancer Cells | - Cancer cells do not respond to signals that regulate the cell cycle and excessively divide & invade other tissues.
- They do not stop dividing when growth factors are depleted.
- One hypothesis is that they do not need growth factors in their culture medium to grow/divide.
- Another possibility is an abnormal cell cycle control system.
- When cancer cells stop dividing they do so at random points in the cycle.
- Cancer cells also can go on dividing if they have a continual supply of nutrients. | | 42 |
| 5140416079 | Transformation | - The process that converts a normal cell to a cancer cell.
- The body's immune system normally recognizes a transformed cell as an insurgent and destroys it.
- However, it a cell does not destroy it, it may proliferate and form a tumor (a mass of abnormal cells within otherwise normal tissue) | | 43 |
| 5140416080 | Benign Tumor | - An abnormal mass of cells that remains at its original site in the body. | | 44 |
| 5140416081 | Malignant tumor | - An abnormal tissue mass that can spread into neighboring tissue and to other parts of the body; a cancerous tumor.
- Cells of malignant tumors may have unusual #s of chromosomes, their metabolism may be disabled, and they may stop functioning correctly. | | 45 |
| 5140416082 | Metastasis | - The spread of cancer cells to locations distant from their original site
- Changes on the cell surface can also cause cancer cells to lose attachments to neighboring cells and the extracellular matrix allowing them to spread into nearby tissue.
- They may also secrete signaling molecules that cause blood vessels to grow toward the tumor and tumor cells may separate and enter blood & lymph vessels traveling to other parts of the body. | | 46 |
| 5140416083 | Treating cancer cells | - High-energy radiation may be used which damages DNA in cancer cells.
- Chemotherapy can be used to treat known metazoic tumors in which drugs that are toxic to actively dividing cells are administered through the circulatory system.
- The drug Taxol freezes the mitotic spindle and stops divine cells from proceeding past metaphase.
- Side of chemotherapy arise from the drugs' effect on normal cells. | | 47 |
