1. CELL CYCLE
Molecular biology
lab 2

2. Cell cycle
The cell cycle, or cell-division cycle, is the series of events that takes place in a cell leading to its division and duplication (replication).
In prokaryotes, the cell cycle occurs via a process termed binary fission.
In eukaryotes, the cell cycle can be divided in two brief periods:
interphase—during which the cell grows, accumulating nutrients needed for mitosis and duplicating its DNA
mitosis (M) phase, during which the cell splits itself into two distinct cells, often called "daughter cells".
The cell-division cycle is a vital process by which a single-celled fertilized egg develops into a mature organism, as well as the process by which hair, skin, blood cells, and some internal organs are renewed.

3. I = Interphase, M = Mitosis, G1 = Gap 1, G2 = Gap 2, S = Synthesis, G0 = Gap 0/Resting

4. Phases of the cell cycle
The cell cycle consists of:
Interphase (cell growth and copying of chromosomes (DNA replication) in preparation for cell division)
Interphase (about 90% of the cell cycle) can be divided into subphases:
G1 phase (“first gap”)
S phase (“synthesis”)
G2 phase (“second gap”)
B. Mitotic (M) phase (mitosis and cytokinesis)

5. Interphase G1 phase (Gap 1 phase): It is also called the growth phase.
Cells increase in size
During this phase the biosynthetic activities of the cell resume at a high rate.
synthesis of various enzymes that are required in S phase, mainly those needed for DNA replication.

6. Interphase Resting (G0 phase)
A resting phase where the cell has left the cycle and has stopped dividing.
some cells in eukaryotes generally enter the stopped G0 state from G1 and may remain inactive for long periods of time (such as Nerve cells and Muscle cells).
It occurs in response to DNA damage or degradation that would make a cell's progeny nonviable.

7. Interphase 2. S phase (Synthesis phase)
The major event in S-phase is DNA replication.
S phase starts when DNA synthesis starts. When it is complete, all of the chromosomes have been replicated, i.e., each chromosome has two (sister) chromatids. Thus, during this phase, the amount of DNA in the cell has effectively doubled.

8. Interphase G2 phase (Gap2 phase)
Again, significant biosynthesis occurs during this phase, mainly involving the production of microtubules, which are required during the process of mitosis.

9. B. Mitotic phase (M phase)
The mitosis phase consists of nuclear division . The mitosis phase has been broken down into several distinct phases:
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
cytokinesis (it is not part of mitosis but is an event that directly follows mitosis in which cytoplasm is divided into two daughter cells).

10. Prophase Major processes during this phase:
Chromosomes condense and form visible bodies
Chromosomes become thicker, shorter, and easily visible when stained under the light microscope.
Two “sister chromatids” join near their middle at a structure called the centromere.
The nucleolus and the nuclear membrane disappear. The mitotic apparatus the spindle, begins to organize within the cell

11. Prometaphase :
stage between prophase and metaphase in mitosis in which the nuclear membrane disappears and the spindle forms

12. Metaphase:
Chromosomes become aligned at midpoint or equator between poles of the cell
are at their thickest and shortest structure.
They are easily identified as two sister chromatids

13. Anaphase: The centromere replicates and splits
The sister chromatids separate and are pulled to opposite sides of the cell

14. Telophase: Chromosomes now uncoil
Nuclear envelope reappears and surrounds the chromosomes

15. Cytokinesis Cytokinesis
The cytoplasm and all its contents are divided between the 2 daughter cells (cytoplasmic division)
membrane creates between the 2 new daughter cells
In plants, such as the onion root tip cells,
this is seen as the formation of a cell plate

16. B. Mitosis phase (M phase)

17. B. Mitotic (M) phase (mitosis and cytokinesis)