Youtube channel name: https://www.youtube.com/channel/UCHFn_vAYMkBJeRmT6erWdyw

Cell cycle, or cell-division cycle in eukaryotes

1.      The sequence of events in a cell to produce two daughter cells.

2.      two main stages:

a.       interphase -the cell grows, gathering nutrients and DNA replication (preparatory phase or intermitosis which covers at least 91% of time for the cell cycle and has

three stages.

                                                              i.      G1 phase / First growth phase / Post mitotic gap. The biosynthetic activities of the cell, restart at a high rate. The cell surges its stock of proteins, increases the number of organelles like mitochondria, ribosomes thereby growing in size. After G1 phase, a cell go into S phase or go to  G0 phase

                                                            ii.      S phase for DNA replication. Amounts of protein synthesis and RNA transcription are less. But histone production rate is very high. S phase ends when all the chromosomes have been replicated (every chromosome has two chromatids)

                                                          iii.      G2 phase (growth) G2 high rate of protein synthesis cell. Microtubules rearrange to form a spindle (preprophase).

b.      the mitotic (M) the replicated chromosomes and cytoplasm disperse into two new daughter cells. Faults in mitosis can lead to in cell death or mutations

                                                              i.      nuclear division / karyokinesis where cell splits the chromosomes in its cell nucleus into two matching groups in two nuclei as pairs of chromosomes shrink and fasten to microtubules that attracting the sister chromatids to opposite sides of the cellIt is a short period of the cell cycle consisting of

1.      prophase (condensation of the chromatin and the disappearance of the nucleolus)

2.      prometaphase (nuclear membrane disrupts into many "membrane vesicles")

3.      metaphase (chromosomes align in the equator of the cell)

4.      anaphase (Chromosomes attain their overall maximum condensation)

5.      telophase (the results of prophase and prometaphase including nuclear membrane and nucleolus crumbling are overturned. The chromosomes go to the cell poles, the nucleoli resurface, and chromosomes start to decondense)

                                                            ii.      cytokinesis, Division of the nuclei, cytoplasm, organelles and cell membrane into two cells (identical to the parent cell and to each other) comprising approximately identical cellular components,

3.      The cell-division cycle is a vital process by which a single-celled fertilized egg develops into a mature organism,

4.      It is procedure followed for the renewal of hair, skin, blood cells, and internal organs

5.      Cell division is followed by the initiation of the interphase of a new cycle in each of the daughter cells.

6.      G0 phase is the resting phase of cells that have temporarily or reversibly stopped dividing

7.      Most nerve cells do not undergo cell division and for this reason people suffering from nerve damage ultimately permanently become patients of motor or sensory deficits

8.      Regulation of the cell cycle for the discovery and restoration of genetic damage and inhibition of uncontrolled cell division through two main classes of regulatory molecules, called cyclins and cyclin-dependent kinases

9.      Cell cycle has checkpoints to observe and control the advancement of the cell cycle. The cell cannot continue to the next phase before meeting. Three main checkpoints are the G1/S checkpoint (restriction point to check enough raw materials is available to fully replicate DNA), the G2/M checkpoint and the metaphase (mitotic) checkpoint.

10.  Mutation of cell cycle inhibitors, RB, p53 cause cell to multiply uncontrollably