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Mitosis and Meiosis in Plant Cell
CELL CYCLE
INTERPHASE
•Gap 1 (G1)
•Synthesis (S)
•Gap 2 (G2)
MITOSIS
•Shortest part of cell cycle
•All somatic cells
•Daughter cells have the same number and kind of chromosomes
•Increases the number of cells (growth)
•Repair of damaged cells and cells that die from accidents (normal wear and tear)
MITOSIS
Prophase
•Chromatin to chromosomes
•Chromosomes: 2 chromatids joined by centromere
•Disintegration of nuclear envelope and nucleoli
•Formation of spindle fibers (visible)
MITOSIS
Metaphase
Chromosomes aligned at equatorial plate (Metaphase plate)
MITOSIS
Anaphase
•Paired centromere of each chromosome separate
•Movement to opposite poles
MITOSIS
Telophase
•Spindle fibers disappear
•Cell plate is visible
•Formation of nuclear envelope and nucleoli
•Dispersal of chromosome mass
•Cytokinesis
MITOSIS
Telophase
MITOSIS
Telophase
Cytokinesis – vesicles from golgi apparatus move along microtubules to the cell where they coalesce forming cell plate.
MEIOSIS
MEIOSIS I
Extra pictures
Interphase metaphase 1
Prophase I
• condensation of chromatin;
•members of each homologous pair synapse;
•crossing over between synapsed pairs occurs;
•Nucleolus and nuclear envelope break down ;
• two centromeres of each tetrad attach to spindle fibers
•Homologous chromosomes- chromosomes that exist in pairs; pair shares the same same genetic loci and centromere placement; pair also has identical gene sites (locus) along their lengths
Metaphase I
•Chromosomes have maximally shortened
•Homologous pairs align at metaphase plate
Anaphase I
•single centromere holds each pair of sister chromatids together;
•each dyad is pulled toward each pole;
Telophase I
•sister chromatids arrive at the opposite poles;
•each daughter cell has half the number of chromosomes;
MEIOSIS II
Prophase II
•Succeeds interkinesis
•Chromosomes condense once more (dyad)
• Nucleolus and nuclear envelope disintegrates
Metaphase II
Chromosomes align at metaphase plate
Anaphase II
•separated sister chromatids move toward the poles;
Telophase II
•separated sister chromatids (chromosomes) arrive at the poles; •chromosomes uncoil;•nuclei form around chromosomes;•after cytokinesis, four haploid gamets are formed
Summary
Similarities• Both Mitosis and Meiosis are forms of cell division.
• Both Mitosis and Meiosis allow for replication. Mitosis leads to cellular replication. Meiosis leads to organism replication.
• Both Mitosis and Meiosis occur within the nucleus of the cell and go through the same steps known as Prophase, Metaphase, Anaphase and Telophase.
Criteria Mitosis Meiosis
Type of cells Occurs in somatic cells Occurs in reproductive cells
Number of division Consists of only one nuclear division
Consists of two nuclear division M-I and M-II
Product/ Chromosome number 2 diploid daughter cells 4 haploid daughter cells
Cytokinesis Occurs only once – Telophase Occurs twice-Telophase I and II
Pairing of homologues Yes No
Crossing over Does not occur Mixing of chromosomes during prophase I
Function Helps in growth and body repairs Helps in the sexual reproduction and regulation of chromosome number in the life cycle of sexually reproducing organism.
DIFFERENCES
Prophase Involves relatively few changes. Involves a series of changes in
chromosomes distinguished into 5 substages.
Metaphase Chromosomes arrange along the equator.
Chromosomes arrange equally on either side of the equator in metaphase-I.
Centromeres in Anaphase Each centromere splits into two. Centromeres do not split in metaphase-l.
Centrome- res in Metaphase Orient towards the equator
while chromatids orient towards poles.
Orient towards poles while chromatids orient towards the equator in metaphase-I.
Telophase
Results in the formation of two daughter nuclei having the same no. of chromosomes as that of parent cell.
Telophase-II results in the formation of two daughter nuclei, each having half the no. of chromosomes as that of parent cell.
Cytokine- sis Follows immediately after karyokinesis.
May or may not occur at the end of first karyokinesis.