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38 Cards in this Set
- Front
- Back
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Where do cells come from?
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Cells come from other cells through cell division.
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Why do cells divide?
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1) Repair
2) Growth 3) Reproduction |
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What's the only reason single-celled organisms divide?
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For reproduction.
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Cell division in prokaryotes (Bacteria)
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Single-celled organisms.
Have one CIRCULAR chromosome. --copied by DNA replication |
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How do cells divide?
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Binary Fission.
--Not mitosis or meiosis. --Cells always divide with adequate nutrients. --Chromosomes are anchored to the cell membrane. |
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Why is eukaryotic cell division more complicated?
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1) Membrane-bound organelles
--mitochondira, chloroplasts (divide themselves) --ER, golgi (disintegrates) 2) Multiple chromosomes |
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What are the two types of cell division in eukaryotes?
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Meiosis, Mitosis.
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Mitosis V.S. Meiosis
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Mitosis: Produces daughter cells that are identical to the parent. For growth, repair/regeneration.
Meiosis: Produces daughter cells with 1/2 the number of chromosomes. For reproduction. |
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Where does Mitosis occur?
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Body cells = somatic cells.
Not egg cells or sperm cells. |
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When does mitosis occur?
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At the end of the cell cycle.
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The Cell Cycle
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A tightly regulated series of events, unique to eukaryotes.
Cell division occurs during the "M phase". The rest of the cycle is Interphase. --Between cell division --90% of the process Among the most intensely studied processes. |
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What is this process controlled by?
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Many enzymes.
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Interphase has 3 subphases:
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S phase
--Chromosome duplication --DNA synthesis (replication) Two gap phases: G1, G2. --Separate M and S --G1: Special growth. Prep for S phase. Biggest phase --G2: Slightly more growth. Prep for M phase. |
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M phase has two parts:
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Mitosis
--Division of the nucleus. Cytokinesis --Division of the cytoplasm. |
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G0 Phase
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Cells can LEAVE the cell cycle, and enter a non-dividing state. The best time to go into G0 is at the end of G1.
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Why is the nuclear DNA carefully inspected in both gap phases?
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For damage. Damaged Cells -> Mutations-> Cancer.
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How often do cells 'cycle'?
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This depends upon the type of cell.
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Three Frequencies of Mitosis
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1) Continuous (GI Tract)
2) Based on need (Liver) 3) Rare/never (neurons/muscle cells) |
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When can G0 occur in these frequencies?
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Only in 2 (need), and 3 (rare/never). Only 2 can re-enter.
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What are most human cells in?
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G0.
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During the cell cycle, how can genetic material become more or less compact?
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Nuclear DNA is wrapped around protein, this complex material is called chromatin.
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Why is chromatin wrapped around protein?
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It helps it regulate/organize.
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How much DNA does one human cell contain?
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About 6 feet.
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During the M phase, the DNA is...
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Tightly packed, this allows individual chromosomes become visible.
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Chromosomes (in eukaryotic cells)
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One DNA molecule PLUS the associated proteins.
-- A long linear DNA molecule --Contains 100s, 1000s of genes. |
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Each eukaryotic species has a specific number of chromosomes, human cells have...
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46.
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Chromatid
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A replicated chromosome are 2 DNA (two sister chromatid) that went through the S phase. One DNA molecule is called a chromatid. The sister chromatids are identical.
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Centromere
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Where the sister chromatids are held together. After cell division, they disappear.
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A nucleus typically contains...
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A chromatin.
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Mitosis' 5 stages
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1) Prophase
2) Prometaphase 3) Metaphase 4) Anaphase 5) Telophase |
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Mitotic spindle
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Begins to form in the cytoplasm during prophase. Consists of fibers made of microtubules and proteins.
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Centrosome
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The assemble of spindle microtubules start in the centrosome. The centrosome is referred to as the microtubule-organizing center.
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Kinetochore
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The kinetochore is the protein structure on chromatids where the spindle fibers attach during cell division to pull two sister chromatids apart.
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Prophase
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The chromatin condenses into chromosomes in which the chromatin becomes visible.
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Prometaphase
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The nuclear membrane dissolves. Proteins attach to the centromeres creating the kinetochores. Microtubules attach at the kinetochores and the chromosomes begin moving.
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Metaphase
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The centrosomes are at opposite poles of the cell. The chromosomes, now at their most highly coiled and condensed, convene at the metaphase plate. Each chromosome is attached to a kinetochore microtubule.
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Anaphase
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Shortest stage. Sister chromatids separate, become a chromosome, move to opposite poles.
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Telophase
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Two daughter nuclei form in the cell. Chromosomes decondense. Spindle microtubules depolymerize.
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