a series of events that takes place in a cell as it grows and divides.
Cell Cycle
-a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus.
- Results in diploid cells (2n = 46 chromosomes)
- Takes place throughout an organism’s lifetime
- Involved in asexual reproduction
Mitosis
Produces genetically unique cells
- Results in haploid cells (1n = 23 chromosomes)
(needs maternal and paternal cells to complete the 46
chromosomes)
- Takes place only at a certain time in an organism’s
life cycle
- Involved in sexual reproduction
Meiosis
cells that continuously multiply and divide throughout life.
Labile Cell
Type of cell that is present in skin
Epithelial Cells
Does not constantly proliferate
- After it complete the phase, it will stay under G0
phase
- It would only replicate if there is a stimulus
- Liver. Hepatocytes – meaning it would
regenerate.
- Epithelium of kidney tubules and alveolar of the
lungs
Stable cell
- Cells that would no longer proliferate after it undergoes the
cycle - Skeleton muscle, cardiac muscles and neurons
Permanent/Amitotic Cells
-genes that make sures that there is not abnormal
growth of cells. Disruption of cells could cause
cancer cells.
Tumor Suppressor Genes
90% of the process (of the entire cell cycle)
- Mammalian cells = 12-24 hours to complete
interphase
- Root tip = 12-30 hours to complete interphase
Interphase
- Prepares the cell
- Cell would start making more organelles for it to
be enough to replicate the cell - Cell would start synthesizing proteins and
enzymes - Repair of thymidine dimer. It would scan DNA
to make sure that there are no mistakes to avoid
mutation - it is use to synchronize cell during G1 and S
phase - Last for 8 hours or a year depending on a cell
type
G1 Phase (1st Gap Phase)
- Phase quiescent stage
- Rest phase for cells
G0 Phase
- DNA is being replicated to form 2 sister
chromatids, which is held at centromere. - DNA polymerase would help in replication of
DNA - Enzymes would open a bubble in a DNA
strand. As it opens, it would start replicating
for a new strand of DNA - The diploid cell (2n) would now become 2
diploid cells (4n).
S Phase (Synthesis)
- Found in between G1 and S phase
- Make sures that there’s no issue with the
cells and have enough enzymes - DNA would decide if it would divide or not,
or enter rest phase
G1/S phase checkpoint
The cell growth will continue and continue
increase the cytoplasm
- Make sures that everything is equal
- Increase in synthesizing of ATP or energy that is
needed for cell division
G2 Phase
- Cells make sures to prevent damage cells
(damage DNA) - The cell would either repair or stop to
proliferate
G2-M Checkpoint
a condition of the cell where it could no longer
proliferate, even if there is a strong stimulus
present.
Cellular Senescence
Nuclear envelope would start to dissolve.
- There would be a phosphorylation of the Lamin
and the histone would activate proteases and
dissolve the nuclear envelope
- Nucleus would disappear and leave loose
chromatins that would start to condense
- Microtubules organizing center (MTO)
- Would form centrosomes and move apart to
opposite directions
Prophase
imaginary line within the cell
that is where the chromosomes would start to
line up
Metaphase plate
- Centrosomes are already in opposite poles. It
would also start budding out mitotic spindles
and would start attaching to kinetochore. - Kinetochore is a protein that connect
chromosomes to microtubules of mitotic spindle
Metaphase
- The cell would check if the sister chromatids
are correctly attached to the mitotic spindle - If it’s not, it would pause to give time to the
sister chromatids to attached to the mitotic
spindle
M Checkpoint or Spindle Checkpoint
- Mitotic spindle will start pulling the
chromosomes apart. Motor proteins contain
dynein and kinesin - As they separate, they are now called daughter
chromosome - Cohesin – a type of protein that connects
chromosomes in centromere
Anaphase
Spindle fibers will disappear
- Chromosomes would start to uncoil. It would
go back as loose chromatin
- Nuclear envelope or reappearing, as well as the
nucleus.
- It would start constricting to form the cleavage
(myosin protein).
- By creating cleavage furrow, it would now lead
to cytokinesis
- In Plants
- As vesicles became secretary vesicles from
the Golgi apparatus. It is filled with cell wall
components called cellulose.
- Vesicles (cellulose) would build up and
create a cell plate, to become a cell wall in
that would trigger cell division or
cytokinesis
Telophase
- The diploid cell (a result of mitosis) would start
DNA replication and begins Meiosis I. - Homologues are pulled apart and sister
chromatids would stay together. - It will undergo cell division and create 2 haploid
cells
Meiosis I
- Same with prophase in mitosis
- Disappearance of nucleus and nuclear
envelope - Chromosomes condense
- Crossing over occurs. It is an exchange of
genetic information between 2 sister
chromosomes - Proteins will break both DNA strands of the
2 sister chromatids - The chromosomes have swapped each other
DNA information - Every pair of homologous chromosomes
will cross over at least once - At the end of it, it will have recombinant
chromosomes or recombinant DNA
(carrying genes from 2 chromosome)
Prophase I
