Cell Division

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CELL GROWTH

Cells are limited in size by their SURFACE AREA and VOLUME ratio
– meaning that cells can get so large that they can no longer obtain enough oxygen and nutrients
– at which point, cells divide

CELL DIVISION – Process where a cell splits into two identical daughter cells

-Mitosis – division of the nucleus
-Cytokinesis – division of the cytoplasm

CHROMOSOMES

-Made of DNA, found in the nucleus
-Exist as CHROMATIN prior to cell division, then the chromatin coils and becomes CHROMOSOMES
-Number depends on organism (46 for humans, 78 for dogs…etc)
-Each chromosome has a copy of itself (giving it an X -shape), the two individuals CHROMATIDS are held together by a CENTROMERE

CELL CYCLE - events cells go through as they grow and divide.   Interphase –> Mitosis –> Cytokinesis

*Note that a cell spends the majority of its life in interphase, which is divided into three phases:  Growth 1 (regular cell growth),  Synthesis (DNA replicates), and Growth 2 (organelles double in number).

The time it takes for mitosis to complete varies by cell (and by organism), the process can take a few hours.

=======>  Helpful to remember the steps of the cell cycle

Interphase

Organelles double in number  to prepare for division
DNA replicates (copies)
Chromatin coils and becomes chromosomes


MITOSIS

CYTOKINESIS – the process by which the cytoplasm divides and one cell becomes two individual cells.  The process differs slightly in plants and animals.

In plants, a new cell wall is built between the cells.

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