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First understanding the packaging of DNA in chromosome.
- DNA is not packaged directly into final structure of chromatin
- First the winding of DNA around a protein core to produce nucleosome which is "bead-like" structure.
- Then packing and coiling of beads in a helical structure called the 30 nm fiber.
- Finaly packaging occurs, the fibers are organized in loops, scaffolds and domains that give a final packing ratio of chromosome.
Second understanding phases of cell cycle.
G1 phase, S phase (synthesis), G2 phase and M phase. G1, S and G2 are collectively known as interphase. M phase is mitosis.
G1 phase at this phase the cell ensures that everything is ready for DNA synthesis.
S phase DNA synthesis occurs
G2 phase at this phase cell ensure everything is ready for M phase.
M phase the parent cell is divided into two daughter cells. During mitosis the chromosomes condense to which fibres are attached that pull the chromosome in oppt direction due to which sister chromatids are formed. Then cytokines takes place and cell is divided into two individual cells.
During cell division the chromosome divides into chromatids in which the genetic material are organised. During division the sister chromatids of a chromosome separates followed by cytokinesis and forming individual cells.
Chromatin refers to the DNA and proteins found inside the nucleus of a cell. Chromatin allows for the hereditary material or DNA to be packaged in such a way that it actually can fit inside the cell's nucleus. It helps control gene expression and prevent DNA from being damaged. This is accomplished by histones--proteins that DNA winds around, much like a ball of yarn helps minimize the space that all that yarn would take up if it were stretched out. During interphase, which is the resting stage between mitotic divisions, chromatin is loose to allow the transcription and replication of DNA to occur. Also, it allows for DNA repair factors to access the DNA to complete any repairs. However, when a cell enters the mitotic phase of the cycle, the chromatin packages more tightly into chromosomes.
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