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Cell Cycle - Coggle Diagram
Cell Cycle
Mitosis
Prophase
Early Prophase
- Cell membrane decreases
- Chromatin fibres become more tightly coiled -> condense into chromosomes
- Nucleoli disappear
- Mitotic spindle (2 centrosomes + microtubules) begins to form
- Centrosomes moves away from each other
Late Prophase
- Nuclear envelope fragments (for the attachment of spindle fibres)
- Microtubules extending from each centrosome can invade nuclear area
- Chromosomes more condensed
- Kinetochore form at the centromere of each chromatid
-
Anaphase
- Cohesin proteins cleaved -> allow two sister chromatids of each pair to part
- two daughter chromosomes begin moving toward opposite poles of the cell
- Cell elongates
- centrioles move towards opposite poles
-
Metaphase
- Centrosome are at opposite poles
- Chromosome at metaphase plate
- Kinetochore attached to kinetochore microtubules
- Microtubules attach to kinetochore
Telophase
- Two daughter nuclei form
- Nuclear envelope arise
- Nucleoli reappear
- Chromosome less condense
- Spindle microtubules depolymerised
Significance of Mitosis
a. Increase the no. of cells
b. Repair worn-out cells and replace them with new cells
c. Advantage to organisms to produce asexually in stable environment
d. Maintain chromosome no. of an organism
Meiosis
Meiosis
Prophase I
- Cell surface membrane decreases
- Nuclear envelope fragments, Spindle fibres form, Centrosomes move away from each other
- Chromosome condense progressively
- Nucleoli disappears
Early Prophase
- Each chromosome pairs up with its homologue -> crossing over -> DNA molecules of non sister chromatids are broken and rejoined
- Chiasmata (point of crossing over) occur
Late Prophase
- Microtubules attach to two kinetochores
- Kinetochore microtubules move the homologous pairs toward the metaphase plate
Metaphase I
- Pairs of the homologous chromosomes are now arranged on the metaphase plate
- Sister chromatids of one homologue are attached to kinetochore microtubules
Telophase I
- Two daughter nuclei form
- Nuclear envelope arise
- Nucleoli reappear
- Chromosome less condense
- Spindle microtubules depolymerised
Anaphase I
- Homologues move to opposite poles
- Sister chromatid cohesion persists at the centromere, causing the sister chromatid to move as a unit
- Cell surface membrane increase due to the concerted fusion of endosomes
a cell division that results in 4 daughter cells with half the number of chromosomes sets as a parent cell
Meiosis II
Metaphase II
- Chromosomes are postitioned on the metaphase plate
- Kinetochores of sister chromatids attached to kinetochore microtubules eztending from opposite poles
Prophase II
- Spindle fibres form
- Late prophase II, two sister chromatids move towards metaphase plate by kinetochore microtubules
Telophase II
- Two daughter nuclei form
- Nuclear envelope arise
- Nucleoli reappear
- Chromosome less condense
- Spindle microtubules depolymerised
Anaphase II
- Cohesin protein cleaves
- Separated sister chromatids move towards opposite poles as indivivual chromosome
Significance of Meiosis
a. Haploid gametes for sexual reproduction
- fertilisation, nuclei of two gametes fuse to produce a zygote
- enables the diploid condition (2n) to be restored and maintained
b. Increase genetic variation
i. Crossing over between non-sister chromatids of homologous chromosomes (prophase I)
- genetic exchange between pair of homologous chromosome
- produce chromosomes with new combinations of alleles (ie. recombinant chromosomes)
ii . Independent Assortment of chromosome (metaphase I)
- sister chromatids of each chromosome is postitioned on the metaphase plate independently of that of other chromosomes at metaphase II
Cytokinesis
Animal Cell
- Formation of cleavage furrow
- Actin microfilaments interact with myosin molecules, causing ring to contract
- Cleavage furrow deepens until parent cell pinch into two -> produce two separate cells
Plant cell
NO CLEAVAGE FURROW
- During telophase, vesicles from golgi apparatus move along microtubules to the middle of the cell -> produce cell plate
- Cell wall materials in the vesicles collect in the cell plate as it grows
- Cell plate enlarge until surrounding membrane fuse with cell surface membrane
-> form two daughter cells
Interphase
1. G1
- organelles are replicated
- protein synthesis
- cell size increase
2. S phase
- all of the chromosome are replicated
- amt of DNA doubled
3. G2 phase
- preparations are made for genomic separation
- mitochondria and other organelles replicate
- protein synthesis occur
- cell size increases