What is Cell Cycle? What are the Different Phases of a Cell Cycle?
Complete lifecycle of a cell is called the cell cycle. In other words, it is an orderly series of changes that occurs in a cell by which the cell duplicates its genetic material along with that it duplicates other content; finally, it divides and results in the formation of two daughter cells. An interphase occurs between two phases. During interphase, a cell grows in size and prepares itself for the next division. Interphase is also the most active phase of a cell cycle. During this phase, the metabolism activity of cell increases and a series of changes occur during the same phase. However, these changes are not visible under the microscope. That is why some scientists have termed interphase as a Resting Phase. Howard and Pelc -- two scientists have classified interphase into three sub-stages:
The time taken by the cell to divide is known as generation time. For yeast, generation time is about 90 minutes.
(I) G1 Phase / Pre-DNA synthesis phase / Post-mitotic phase:
-- Maximum growth of the cell along with an increase in the size of the nucleus is seen.
-- It is the longest duration of the Interphase
-- During this phase, there is synthesis of nucleotides / amino acids / energy-rich molecules (ATP)
-- Polymerisation of nucleotide results in RNA synthesis.
-- RNA polymerase becomes active along with the enzymes for DNA synthesis.an
-- Synthesis of amino acids, which are involved in histone protein synthesis.
(II) S-Phase (DNA Synthesis Phase):
-- DNA duplication / replication takes place.
-- Chromosome consists of two chromatids
-- Centriole duplication occurs in the cytoplasm
-- Amino acids polymerize and form histone proteins
-- Assembly of kinetochore subunits
-- The duplicated chromosomes will not appear during this phase and that's why this phase is known as INVISIBLE PHASE
G2-Phase / Post-DNA synthesis phase / Pre-mitosis phase
-- Known as the second growth phase.
-- Cell size increases
-- Nucleus size increase
-- RNA synthesis takes place
-- Protein synthesis takes place
-- Duplication of most of the cell organelles (along with the division of mitochondria and division of plastids)
-- Biochemicals are formed for the synthesis of spindle fibres.
-- Tubulin protein synthesis takes place.
-- It is also signified by the synthesis of some protein kinases for the regulation of cell division
The time taken by the cell to divide is known as generation time. For yeast, generation time is about 90 minutes.
(I) G1 Phase / Pre-DNA synthesis phase / Post-mitotic phase:
-- Maximum growth of the cell along with an increase in the size of the nucleus is seen.
-- It is the longest duration of the Interphase
-- During this phase, there is synthesis of nucleotides / amino acids / energy-rich molecules (ATP)
-- Polymerisation of nucleotide results in RNA synthesis.
-- RNA polymerase becomes active along with the enzymes for DNA synthesis.an
-- Synthesis of amino acids, which are involved in histone protein synthesis.
(II) S-Phase (DNA Synthesis Phase):
-- DNA duplication / replication takes place.
-- Chromosome consists of two chromatids
-- Centriole duplication occurs in the cytoplasm
-- Amino acids polymerize and form histone proteins
-- Assembly of kinetochore subunits
-- The duplicated chromosomes will not appear during this phase and that's why this phase is known as INVISIBLE PHASE
G2-Phase / Post-DNA synthesis phase / Pre-mitosis phase
-- Known as the second growth phase.
-- Cell size increases
-- Nucleus size increase
-- RNA synthesis takes place
-- Protein synthesis takes place
-- Duplication of most of the cell organelles (along with the division of mitochondria and division of plastids)
-- Biochemicals are formed for the synthesis of spindle fibres.
-- Tubulin protein synthesis takes place.
-- It is also signified by the synthesis of some protein kinases for the regulation of cell division