• Growth and reproduction are characteristics of cells, of all living organisms. each
parental cell gives rise to two daughter cells when it divides. These newly formed
daughter cells can themselves grow and divide, giving rise to a new cell population.
In unicellular organisms, cell division is equivalent to cell reproduction as it gives
rise to new independent unicellular organism. Whereas in case of multicellular
organisms, cycles of growth and division allow a single cell to form a structure
consisting of millions of cells.
• Rudolf Virchow (1855) first explained that new cells are formed from the division
of the pre-existing cells– omnis cellula-e cellula (every cell is derived from a pre-
existing cell).cell cycle
• The sequence of events by which a cell duplicates its genome, synthesises other
constituents of the cell and eventually divides into two daughter cells is termed cell
cycle (Howard and Pelc, 1953). all these events occur in a coordinated manner and
are under genetic control.Phases of cell cycle
• The cell cycle is divided into two basic phases: I-phase or interphase and
M-phase or mitotic phase.
• I-phase is a long nondividing growing phase and M-phase is short dividing phase.
Interphase
• Interphase (L. inter– between, GK. phasis– aspect) is a series of changes that take
place in a newly formed cell and its nucleus before it becomes capable of division
again. Therefore, it is also called intermitosis.
• Interphase, the so called “resting stage” is infact the period of great activity as
three important processes, which are preparatory to cell division, take place during
interphase. Hence, it is also known as preparatory phase.
FACTS
HGH
YIELD
Class XI
Cell Cycle and Cell Division
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