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.