Home » Mitosis and Meiosis

Key Terms

Cell skeleton:  Composed of microtubules made of tubulin and actin, plays roles in maintaining cell shape, cell motion, intra-cellular transport and cell division –both mitosis and meiosis.
Centrosome:  Made of two centrioles, it is the main microtubule organizing center (MTOC) and a regulator of cell-cycle progression.
Mitotic spindle: A dynamic protein structure assembled at early mitosis stage, consisting of a bundle of microtubules joined at the ends but spread out in the middle.  The function is to pull chromosomes to two opposite poles.
Kinetochore: The protein structure assembled on the centromere and links the chromosome to microtubules from the mitotic spindle.
Diploid Number (2N):  The total number of chromosomes present in a somatic cell containing 1 pair of homologous chromosomes. 
C Value: The total amount of DNA in a haploid cell. 
Cytokinesis: The division of the cytoplasm in a cell, which usually occurs immediately after nuclear division in mitosis.
Sister chromatid: Two identical chromatids after chromosome replication, stay together at the early stage of mitosis but separate later. 
Cell cycle:  Eukaryotic cells keep dividing, the series of events between one cell division and the next is termed cell cycle, normally containing G1, S, G2 and M (mitosis) phases. 
Mitosis:  The series events when a somatic cell is divided into two identical daughter cell.  It normally contains prophase, prometaphase, metaphase, anaphase and telophase. 
Meiosis:  The series events when a cell is divided twice while its DNA only replicate once, resulting 4 haploid progeny cells –germ cells.
Synapsis: a pair of homologous chromosomes lines up closely together
Tetrad: A tetrad is composed of four chromatids, 2 sister chromatids from each of the homologous chromosomes

Mitosis

• DNA replicates once and cell divides once
  
• Sister chromosomes separate
• Resulting daughter cells contain one set of homologous chromosomes each

Meiosis

Stages of Mitosis and Meiosis

Prophase:

• Chromatin condense to form chromosomes
• Nucleolus disappears
• Centrosomes are duplicated and begin moving to opposite poles
• Formation of mitotic spindle

Prometaphase (for mitosis only):  

• The nuclear membrane starts to dissolve
• Kinetochores formation
• Microtubules from spindles attach at the kinetochores and the chromosomes begin moving 

Metaphase:

• Chromosomes are aligned on the metaphase plate

Anaphase:

• The sister chromotids separate at the kinetochores (for mitosis); Homologous chromosome separate (meiosis anaphase I) or sister chromosome separate (meiosis anaphase II)
• The separated chromosomes move to opposite sides of the cell.

Telophase:

• New membranes form around the daughter nuclei.
• The chromosomes disperse and are no longer visible under the light microscope. 
• The spindle disembles
• Cytokinesis occurs

The Major Difference

Mitosis:

For somatic cell proliferation

Meiosis: