Class 11 Biology Notes – Cell Cycle and Cell Division (NCERT-based)

Cell cycle and Cell division
CELL CYCLE
● Two main stages
● 1.interphase- preparation
● 2.m phase (mitosis)- division
● Interphase is large with 95% of cell
CYCLE


INTERPHASE
● Can be divided into 3
● 1.G1 phase-gap 1 phase
● Cell growth
● cytoplasm increases
● Cell will be metabolically active
● Continuously grow but does not replicate its DNA

● 2. S phase-synthesis phase
● DNA synthesis or Replication takes place
● Amount of DNA for cell double but number of chromosomes
remain the same

● 3.G2 phase- gap 2 phase
● Final preparation for division
● Protein synthesis for Mitosis

● G0 phase-quiescent phase

, Some cells that Do not divide further except G1 phase to enter
an Inactive stage called quiscent stage the (G0)of the cell cycle
cells .cells in the stage remain metabolically active but no
longer profilarate unless called on to do so depending on the
requirement of the organism


M phase (mitosis)
● It is known as equational division as there is no change
in the chromosome number in parent and daughter cell
during and after division
● There are two stages
● 1.karyokinesis (nuclear divison) 2.cytokinesis
● Karyokinesis Can be further divided into four stages
● Prophase
● Metaphase
● anaphase
● Telophase




PROPHASE
● Early prophase to late prophase
● Chromatin reticulum condense To form
chromosome
● centrioles move to opposite poles
● Initiation of Spindle fibers
● Cell organelles disappear
● nuclear membrane disappear