Mitosis

 “Where a cell exists, there must have been a preexisting cell”
 “Omnis cellula e cellula”
(all cells come from cells)

Necessary Characteristic of Life: Cell
Reproduction
 unicellular organism
 reproduces entire organism
 multicellular
 growth
 embryonic development
 replacement of damaged or dead cells

Binary Fission
Reproduction in Bacteria
 genome (hereditary endowment)
 single, circular dsDNA
 associated with proteins
 single chromosome
 replication averages minutes-3 hours


Steps of Binary
Fission chromosome replication begins, one copy of the origin moves rapidly to the other end
 one copy of the origin is now at each end of the cell; the cell elongates
 replication finishes, the plasma membrane grows inward and a new cell wall is formed
 resulting in two daughter cells

larger cell size greater quantity of DNA
Histones several chromosomes smaller cell size lesser quantity of DNA other proteins one chromosome

 Amount of DNA has no direct relationship to the complexity of that organism
 ex.


Alligators have more DNA than humans frogs have more DNA than humans

 Chromosomes
 discrete entities
 condensed DNA + protein
 state found when DNA division occurs
 Chromatin
 mass of DNA
 loose coils of DNA + protein
 state found when DNA replication occurs

short arms kinetochore (protein) centromere sister chromatids long arms sister chromatids www.biologycorner.com

 composition

DNA = 40%
 protein = 60%
 average human chromosome

5 cm (2.5cm = 1 in)
 46 chromosomes in each cell

2 meters of DNA

6 Billion base pairs

 particular array of chromosomes
 chromosomes of one cell are arranged according to:
 size
 number
 type information extra or missing DNA gender of individual www.biotechnologyonline.gov.au/images/contentpages/karyotype.jpg

 somatic cells = body cells

46 chromosomes
 diploid (2n)
 gametes = sex cells (sperm, ova)

23 chromosomes
 haploid number (1n or n)

 pair of chromosomes
 one paternal, one maternal

 identical
 replicated forms of one chromosome
 held together by one centromere

 Homologous (2)
 maternal, paternal


Replicated (2)
4 sister chromatids http://www.phschool.com/science/biology_place/labbench/lab3/images/homologs.gif

 autosomal chromosomes

22 pairs
 sex chromosomes

1 pair, XX or XY

 Interphase

G1 phase

S

G2 phase
 M (mitotic) phase
 mitosis (P, M, A, T)
 cytokinesis

 Preparing a cell for division
G
1 phase (first gap) growth of cell, enough cytosol for 2
S (synthesis)
DNA replication, DNA in chromatin
G
2 phase (second gap) chromosome condensation microtubule synthesis

 Mitosis (karyokinesis) - divide DNA, precise division
 prophase (prometaphase)
 metaphase
 anaphase
 telophase
 Cytokinesis - divide the cytoplasm, rough division

Mitosis
Prophase-Prometaphase


Prophase

DNA condenses



 nucleoli disappear sister chromatids visible spindle is forming centrosomes migrate
Prometaphase




 nuclear envelope disappear centromeres are at poles condensation increases kinetochore present microtubules attach to kinetochore

 centrosomes convene at the equator (plate)
 kinetochores have both microtubules from the opposite poles attached to each one

 proteins maintaining the chromosomes attached split
 daughter chromosomes move to the poles
 cell elongates

 2 daughter nuclei form
 nuclear envelopes form
 nucleoli reappear
 chromosomes become less condense
 END of Mitosis

Cytokinesis
(division of cytoplasm)
Animals Plants microfilaments form contractile ring and cell pinches in two vesicles form plasma membrane, cell wall material is deposited cleavage furrow cell plate

 varies from 1-24 hours
 example human liver cell


Interphase:


G
1 phase…………......9 hrs.
S…………………..…10 hrs.
 G
2 phase……..………2 hrs
M phase: mitosis……50 min.

Cytokinesis……….....10 min

Controls of Cell Division
Cells in tissue culture do not divide if
1. essential nutrients are missing (growth factors)
2. poisons that inhibit protein (microtubules) synthesis are present
3. cells are crowded
4. they cannot progress beyond the restriction point in late G 1
5. insufficient concentration of MPF (maturation promoting factor, a complex of proteins)
6. they have reached maximum division (20-50x for cells in culture)

 mass of transformed cells
 benign tumor
 cells remain at original site
 lump can be completely removed
 malignant tumor
 invasive cells
 can impair functions of other organs

 express abnormal cell division
1. density-dependent inhibition is absent
2. divide excessively, immortal

HeLa cells 1951
3. can invade other tissues (metastasis)
4. genetically transformed
5. can form malignant tumors
6. can stop dividing at random points in the cycle normal cells cancer cells

ACTIVITIES
F
B
A
E
C what organism is this tissue from?
name the stages A-E which of these is not an M stage?
where in the plant you find this tissue?
what is "F"?
D

 name the stage
 what stage comes before and after it?
 if this is a somatic cell and n=10, how many chromosomes will it have?

 name the stage
 is it part of mitosis?
 give a visible characteristic.
 describe what happens during this stage
The End