Cell cycle and cell reproduction Part 1
○ Life cycle: the sequence of growth and development stages that an organism
goes through during its life.
○ DNA is a double stranded molecule made of four different subunits of
nucleotides ( A ,T, C, G).
○ Chromosomes is a long continuous thread of DNA .
○ Each body cell has 46 chromosomes in 23 pairs.
○ Cells must receive a full set of DNA (no more, no less) to work properly.
○ The scientist Rudolf Virchow in 1858 : each cell arise from a previous cell
○ The cell cycle as a process by which a parent cell grows, duplicates itself and
divides to produce new cells.
○ There's 2 portions of the cell cycle :
interphase which include a number of stages and mitotic stage when mitosis and
cytokinesis occur
○ Cell grows continuously in interphase which consist of three phases
Interphase
○ Interphase is the stage during which the cell grows, develops into a mature,
functional cell, duplicates the DNA in its nucleus, and prepares for division.
○ Interphase is divided into three stages: Gap 1(G1), synthesis (S), and Gap 2
(G2).
○ Gap 1(G1): growing, carrying out normal cellular functions, and preparing to
replicate DNA, (before DNA replication , gap between M phase and S phase )
(Growth)
○ Synthesis (S): copying DNA to prepare for division(DNA synthesis, DNA
replication )
○ Gap 2 (G2): preparing for the division of nucleus (gap between S and M
phase , after DNA replication ) (Growth)
- Interphase prepares the cell to divide (G1, S, G2)
- During interphase, the DNA is duplicated.
- Not a part of mitosis
- During interphase the chromosomes formed of one chromatin is doubled into
two chromatids by a process called duplication or replication.