CELL CYCLEBY NURJULAIHA ROSLAN
CELL CYCLE Sequence of stages between cell
division and the next. Time taken to complete one cell cycle
varies with tissues and among spesis. Enviromental factor such as changes in
temperature and pH and declining nutrients levels lead to declining cell division rates.
Cells cycle involve 3 continuous stages--Interphase-Mitosis-Cytokinesis
INTERPHASE Phase between mitotic
division and appears to be resting phase.
Can be divived to 3 phase
G1 phase S phase G2 phase
G1 PHASE RNA and protein produced. Cells grows rapidly. Chromosomes not yet visible. Organelle grows and increase in size. Nucleolus clearly visible.
S PHASE DNA replicates. Synthesis of Histone proteins. Chromosomes have 2 chromatids. Chromosomes not visible.
G2 PHASE Cells increase in mass. More Mitochondria and Chloroplast. Energy store increase. Chromosome start shorten and
condense. Replication of Centrioles
MITOSIS
mitosis Process of dividing a cell by replication and dividing the original chromosomes to obtain 2 new cells identical to one another.
Divided into 4 stages Prophase Metaphase Anaphase Telophase
PROPHASE Chromatin in nucleus begins to
condense. Nucleolus disappear. Mitotic Spindle begin to form. Centrosomes formed and move
apart,push by microtubules. Chromosomes migrate to centre of
nucleus. Disappearance of nuclear envelope.
METAPHASE Nuclear envelope breaks up completely. Centrioles have reaches opposite poles. Attaches to Spindle Fibre in the
Centromere. Chromosomes line up on metaphase
plate.
ANAPHASE Centromere divide and 2 chromatids of
each chromosomes seperates. Spindle Fibre pull the sister chromatids
appart towards opposite pole of cells. Each poles contain a complete set of
chromosomes.
TELOPHASE Spindle fibre disappear and centrioles
divide into two. Chromosomes uncoil and return to
chromatin form. Nuclear envelope reform. Nuclei begin to form.
CYTOKINESIS Splitting the cytoplasm that seperates daughters nuclei into two individual daughter cells.
Furrow forms then it will slowly reduces the diameter of cell until it eventually slices all the way into center of the cell.
Cells seperates completely and 2 complete cell form.
SIGNIFICANCE OF CELL DIVISION
For cell replacement For growth To maintain the genetic stability Reproductive development of organism Continual of life or survival of all
organisms.
WATCH THIS VIDEO!!! For more understanding ,watch this
video through this link.. YouTube - Mitosis.flv or http://www.youtube.com/watch?v=ATlU
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