Cell DIvision/Mitosis

• Cell Division


  process by which multicellular organisms produce more cells.

  This process is related to the ability of living organisms to reproduce.
• For a cell to replicate or divide, it has to double its contents such as water, organelles, and DNA.
• Cell types


  somatic cells and sex cells
• chromosomes


  -refers to a more compressed and coiled status of DNA seen during cell division.

  -The chromosome is seen as the condensed version of the chromatin.

  -consist of the genetic material of organisms
• Somatic cells


  -diploid cells (two sets of chromosomes)

  -They function for growth and various metabolic activities besides reproduction.
• Diploid


  containing two complete sets of chromosomes, one from each parent.
• sex cells(gametes, reproductive cells, germ cells)


  These are haploid cells, the sperm cells and egg cells, that unite during fertilization.
• Cell cycle


  -pertains to the processes happening within the cell as it prepares and executes cell division.

  -consists of the interphase, M phase, and cytokinesis.
• Interphase


  -longest phase which makes up 90 percent of the cell cycle.

  -it is when the cell is active metabolically and prepares for the process of division.

  -dna replicates
• Interphase: G1 phase


  -cell starts to grow.

  -The water content, enzymes, and organelles in the cell are doubled.

  -Majority of growth occurs.
• Interphase: S phase


  -Synthesis phase allows an exact copy of the DNA to be synthesized.

  -This is a prerequisite for cell division so that DNA copies can be distributed to the daughter cells.
• Interphase: G2 phase


  -continuous growth and preparation division.

  -Proteins important the for chromosome and mitotic spindle formation are produced.
• Interphase: G0 phase


  -special phase where the cell is considered to be in a resting state

  (from division).

  -The cell is neither preparing to divide or is currently actively dividing.
• checkpoints: G1


  primarily checks for

  ○ proper cell size

  ○ adequate nutrients

  ○ any DNA damage

  ○ cell growth factors
• checkpoints: G2


  primarily checks for

  ○ proper cell size

  ○ DNA damage from S phase

  -Apoptosis is initiated in

  cases of irreplaceable

  errors.
• checkpoint: Metaphase


  checks for

  -proper and equal separation of these sister chromatids

  -proper attachment of spindles
• Mitotic Phase or Mitosis


  -involves the division of the cellular content. Mitosis has five stages.

  -It is immediately followed by or simultaneously occurs with cytokinesis.

  -used for growth, asexual reproduction, repair and replacement of the body cells

  -the nucleus divies into two identical nuclei

  -begins with 1 parent cell and ends with 2 daughter cells
• Prophase


  ○ nuclear disintegration

  ○ mitotic spindle extends

  from the centrosome

  ○ chromatin condenses

  to become visible

  chromosomes
• Prometaphase


  ○ disappearance of the

  nuclear membrane

  ○ microtubules extend from

  centrosomes

  ○ more condensed

  chromosomes
• Metaphase


  ○ centrosome completely

  located on the opposite

  poles

  ○ chromosomes centrally

  aligned at metaphase plate
• Anaphase


  ○ separation of the sister

  chromatids

  ○ single chromosomes

  move towards the

  opposite poles
• Telophase


  ○ microtubules detach

  from the kinetochore.

  ○ chromosomes start to

  uncoil
• Cytokinesis


  -In animal cells, a cleavage furrow.

  -This furrow starts as a groove along the cell membrane’s surface and then pinches up to the cell’s center.
• Cytokinesis


  -In plant cells a mass of cell wall material is formed called the cell plate.

  -this plate formation starts in the middle of the cell plate and elongates outwardly.