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Loyola Symphony Orchestra

Course Code
ENGL 101

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Exam 3
Fig. 12.4, 12.5, 12.6, 12.7, 12.8, 12.10 and 12.15
Fig. 13.7,13.8 and 13.9
Centromeres area of attachment b/t 2 sister chromatids
Kinetochores structure of proteins & specific sections of chromosomal DNA
at the centromere
Chromatids 2 copies of a duplicated chromosome
Spindle apparatus formed form microtubules extending from 2 centromeres;
as centromeres move away from each the microtubules lengthen
How do cells reproduce?
Cells need to possess the genetic material characteristics of the organism
- Genetic material is DNA
- The “daughter” cells need the complete genetic compliment
Genetic material of prokaryotes = circular DNA
- Replicate the DNA & pass it on to the “daughter” cells
- Divide by binary fission
- A problemthere are multiple chromosomes
- Genetic material is linear chromosomes
- Linear strand of DNA complexed w/ proteins
- Multiple chromosomes
How do you get identical daughter cells? You need a copy of each of the
The solution =
Mitosis - Produces daughter cells with the 2n chromosome number; Diploid
- Reproduction
- Growth
- Repair of tissues
- Produce “daughter” cells that have identical genetic compliments
- Occurs in SOMATIC CELLS (not involved in sexual reproduction)
Somatic Cells
- Do NOT give rise to gametes
- Complex linear DNA & proteins

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- Each eukary species has a characteristic #
- Complex proteins
Duplicated Chromosome
- Consist of 2 sister chromatids
- Identical copies of DNA
- Attached at a specialized region consisting of DNA & proteins called the
- 1 centromere per chromosome
- 1 centromere per chromosome of sister chromatids
Cell Cycle
Mitotic Phase (Mitosis & cytokinesis)
Cytokinesisthink plant cell
- Generally 90% of the cell
- Gap 1 (G1)
- S phase (synthesis of DNA)
- Gap 2 (G2)
Gap 1
- Synthesizing of cell components
- Increase in the # of organelles
S Phase
- Synthesis (replication) of the genetic material (material doubles)
- DNA replicated
Gap 2
- Centrioles replicate in animal cells
- Centriole resembles base of the flagellum?
- Structure for cytokinesis put in place
- In animals
- 9 sets of triplet microtubules arranges in a ring
- Found in the CENTROSOME (a region from which microtubules grow out)

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- Help organize microtubule growth (but centrioles are NOT necessary, most
plants lack centrioles)
* As centrosomes move away from each other the microtubules lengthen
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
- Nucleoli disappear
- Nucleolus (ribosomal subunits are put together)
- Chromatin condenses
- Mitotic spindle forms from microtubules in cytoplasm
- Centrosomes move away from each other
- Nuclear envelope fragments (breaks down)
- Microtubules of spindle invade the nuclear region & interact w/ the
chromosomes via the kinetochore
- Structure proteins & specific sections of chromosomal DNA at the centromere
- Point of attachment for microtubules of the spindle
Mitotic Spindle
- Formed from microtubules extending from the 2 centromeres
- Centrosomes at opposite poles
- Chromosomes arranged at the midplane…
- Sister chromatids separate form one another & move toward the poles
- Nuclear envelope reforms
- Spindle breaks down
- Nucleoli reform
- Chromatids become less densely coiled
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