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FC 2C- Cell Division
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- 1Mitosis vs. Meiosis-MITOSIS produces 2 clones of itself, each with the same number of chromosomes.
-MEIOSIS produces 4 gametes (sperm/eggs) which have 1/2 as many chromosomes as the original cell. - 2ChromosomesMade up of chromatin which is made up of DNA + histones and is stored in nuclei.
Number of total chromosomes in non-gamete cells of a species is its diploid number; haploid is half. - 3MITOSIS InterphaseThe chromosomal DNA strand is replicated and this copied strand is attached to the original strand at the centromere. This new structure is called a bivalent chromosome (2 sister chromatids). When a chromosome exists as just 1 chromatid, just 1DNA strand/its associated proteins, it's monovalent.
- 4MITOSIS ProphaseBivalent chromosomes condense into tight packages. Nucleolus disappears, nuclear envelope becomes tiny vesicles, 2 asters appear, spindle and kinetochores appear, and centriole pairs begin to move to ends
- 5MITOSIS MetaphaseEach chromosome lines up in a single file line at the center of the cell. By this point, the membrane (nuclear envelope) enclosing the nucleus has dissolved, and mitotic spindles at each end have attached themselves to kinetochore of each sister chromatid.
- 6MITOSIS AnaphaseThe mitotic spindle fibers shorten and pry each chromatid apart from its copy, by pulling them to the opposite side of the cell creating a cleavage furrow from contracting microfilaments; 4 bivalent chromosomes become 2 groups of 4 monovalent chromosomes.
- 7MITOSIS TelophaseMembranes form around the 2 groups of decondensed chromosomes, nucleolus becomes visible, and the mitotic spindles that provided the power to create the groups are disassembled. Once mitosis is complete, the cell has two groups of 46 chromosomes and through cytokinesis creates two clones of the original cell, each with 46 monovalent chromosomes.
- 8MEIOSIS ITwo groups of 2 bivalent chromosomes line up 2-by-2 (instead of 2 groups of 4 monovalent lining up in single file) and then separate in anaphase (in mitosis the chromatids separate). Membranes form around the two groups, during telophase, and then the cell splits down the middle creating two non-clones. Each has 1/2n of chromosomes as original.
- 9MEIOSIS IIMeiosis II applies the process of mitosis to the two cells created by meiosis I. Since the chromosomes already exist in the bivalent form, interphase is skipped. The result is 4 gametes, each with 2 monovalent chromosomes.
- 10Cell Cycle-M PHASE: mitosis and cytokinesis
-G1 PHASE: growth
-S PHASE: synthesis (active replication), at the end has 2x's normal DNA
-G2 PHASE: growth
*Interphase (G0) is G1, G2, & S that metabolizes and synthesizes material, no replication/division - 11Growth Arrest-Too much genomic mutation/damage causes a cell to arrest in M phase.
-Contact inhibition: normal epithelial cells stop growing when it gets crowded and touches adjacent cells.
-Lack of food - 12ApoptosisClean and healthy death from caspase activation to digest the cell from within and prevent spilling of cell contents which then releases chemicals that attract macrophages, and gets engulfed. Can be brought upon by development or by immune response.
- 13OncogenesGenes that can convert normal cells into cancer when activated. The product of many oncogenes are involved in speeding up cell division. Before an oncogene is activated, it is a harmless proto-oncogene. The classic example of oncogene is the Src protein.
- 14Cancer-PreventionTummor Suppressor Genes produce proteins that are the inherent defense system to prevent cancer
1) Detect damage to the genome and halt cell growth and division until repaired
2) Trigger programmed cell death if the damage is beyond repair via apoptosis
*p53 is a tumor suppressor gene product and is found in high levels when there is damage/oncogene activity - 15CaspasesCysteine present in active site, ASPartic acid cleavage. Produced as inactive form, procaspases.
-INITIATOR: respond to extracellular or intracellular death signals by clustering together and activating each other and the Effector Caspases
-EFFECTOR: cleave a variety of cellular proteins to trigger apoptosis - 16Cellular Regenerative CapacityRestoring damaged tissue depends on how stem cells are maintained in the organism's body.
*We have MULTIPOTENT stem cells in bone marrow that regenerate blood and immune system's cell components and UNIPOTENT hepatocytes
Ex: dedifferentiate cells then redifferentiate (lizards)
Ex: Extra stem cells floating around (flat worm) - 17SenescenceLength of telomeres is a measure of cellular age and are meant to be maintained by telomerase.
Aged cells become more susceptible to apoptosis.
Accumulation ages the entire organism until the body stops working and dies - 18Gameotogenesisdiploid germ cells -> haploid gametes
The only human process involving meiosis. Germ cells produce gametes (spermatozoa/ova) that fuse via syngamy and germinate to form a zygote. Ova provides every part of the zygote except the genome which is 50/50. - 19Gamete PloidyUnlike sperm, the egg has not completed meiosis - it’s stuck in the Metaphase II stage of division. This means that the egg is haploid but with sister chromatids still attached to each other.
- 20SpermatogenesisOccurs in the seminiferous tubules.
- 21OogenesisOccurs in the ovaries, then fallopian tubes.
- 22Ovum and Sperm Formation Differences1) Spermatogonium renews its population by mitosis throughout life. Oogonium stops renewing its population sometime before birth
2) Primary oocyte arrests at prophase I
3) Secondary oocyte arrests at metaphase II
4) Between the secondary spermatocyte and the sperm, there's the spermatid - 23Implantation1) Zygote
2) Morula (solid ball of 32 cells) made from RAPID mitosis
3) Blastula (sea urchins) or blastocyst (mammals); cellular differentiation
4) Blastocyst is the one that implants in the endometrium - 24Development1) Fertilization:
2) Cleavage:
3) Blastula Formation:
4) Gastrulation:
5) Neurulation: - 25BirthFetal circulation (which bypasses lungs and liver) → normal circulation (by closing off ducts and openings)
- 26Fertilization1) Sperm meets egg
2) Acrosomal reaction causes sperm to penetrate egg
3) Cortical reaction causes egg to prevent additional sperm from penetrating
4) Egg completes meiosis II
5) Sperm and egg nuclei fuse - 27CleavageNormal mitotic cell divisions: cell grows then divides, grows again, then divides.
Cleavage = mitotic divisions without cell growth. - 28Blastula Formation1) Fertilization produces zygote
2) Cleavage produces a solid ball called the morula
3) Morula hollows out into the blastula (non-mammals) or blastocyst(mammals)
4) Blastocyst implants - 29GastrulationFIRST CELL MOVEMENT- Cells from the surface migrate inwards. Some animals proceed by invagination, some migrate (mammals), some split.
FORMATION OF PRIMARY GERMLAYERS - 30Neurulationectoderm → brain and spinal cord
*ectoderm does so by folding into a tube - 31Primary Germ Layers-ENDODERM: innermost layer; epithelial lining of the digestive tract; stomach, colon, liver, pancreas, bladder, lung
-MESODERM: middle layer; muscle, bone, connective tissue, notochord, kidney, gonads, circulatory system
-ECTODERM: outermost layer; epidermis (outer layer of skin), hair, nails, brain, spinal cord, peripheral nervous system - 32PluripotentCells that can eventually turn into the cells of any body tissue, not yet differentiated
- 33The Neural CrestSometimes called the fourth germ layer because it's the cells that become the Sympathetic and Parasympathetic Nervous Systems, melanocytes, Schwann cells, even some of the bones and connective tissue of the face.
- 34EndodermEach subdivision has its own nerve and blood supply.
-FOREGUT: esophagus, stomach, part of the duodenum, and the respiratory bud, which will eventually develop into the lungs.
-MIDGUT: 2nd half of the duodenum through to the transverse colon.
-HINDGUT: the rest of the transverse colon, the descending colon, the sigmoid colon, and the rectum. - 35Cell Specialization-DETERMINATION: irreversible commitment to be a certain cell type.
-DIFFERENTIATION: becoming a cell type and adopting its specialized functions.
-TISSUE TYPES:
1) Epithelial: skin, lining of organs
2) Connective: blood, bone, tendons, ligaments, cartilage
3) Nervous: brain, spinal cord, nerves
4) Muscle: skeletal, smooth, and cardiac muscle - 36Cell Communication in DevelopmentINDUCTION: one group of cells changing the behavior of an adjacent cells.
1) INDUCER- sends the signal for the other to change.
2) RESPONDER- gets the signal/changes.
Induction mechanisms: through JUXTRACINE (physical touching of cells) or PARACRINE (releasing chemicals).
Ex: the optic vesicle is able to induce the ectoderm to develope into lens or the induction of wing feathers in the chick by the dermal mesenchyme. - 37Gene Regulation in Development1) DIFFERENTIAL GENE TRANSCRIPTION:
-Modification of DNA (methylations) can shut off or turn on genes.
-Modification on histones (methylations, acetylations) that wrap the DNA can shut off or turn on genes.
-To make or not to make transcription factors can regulate what genes get transcribed.
2) DIFFERENTIAL RNA PROCESSING:
-Selecting what RNA make it outside the nucleus to be translated.
-Alternative splicing of RNA.
3) TRANSLATION REGULATION:
-Some mRNA are made to last longer than others (more proteins translated off of it), and some are made to be rapidly degraded (less proteins translated off it).
-Selective inhibition of translation of stored RNA in the oocyte. Get translated only when needed after fertilization.
4) POST-TRANSLATIONAL REGULATION
-Some proteins are inactive until modified by certain enzymes.
-Active proteins can be selectively marked for degradation by ubiquitin.
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- Complete Fichas sobre FC 2C- Cell Division, creado por Victoria Whitfield el 09/05/2017.
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- Victoria Whitfield
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