Post on 28-Dec-2015
(1.2) Cell Division(p22-27)
Cell Division
• Cells must divide to survive.• There is a limit to how large a cell can grow.• If the amount of material in a cell is too large
the cell dies.
Cell DivisionWhen a cell divides
- two new cells are created
- each cell is identical to the original cellThe set of instructions each
cell inherits is stored in a unique molecule called DNA (deoxyribonucleic acid).
DNA• DNA in the nucleus of the cell contains the
hereditary material.• DNA molecules have a shape like that of a
ladder.• To fit inside the nucleus DNA forms compact
coiled threads called chromatin.• To reproduce the chromatin packs together to
form chromosomes.• Chromosomes pass on hereditary information
when a cell divides.
DNA• Chromatin are thin threads of DNA.• If the DNA in one of your cells is uncoiled it
would be 2 m long!
ChromatinDNA
Cell Cycle
• The series of events in the life of a cell is called the cell cycle.
• Two main stages:i) growth - called interphaseii) division - consisting of
mitosis and cytokinesis
Growth Stage
• During interphase the cell:- grows- carries out its usual functions- makes copies of its DNA and organelles to
prepare for cell division• Most cells spend most of their lives in
interphase.• Interphase ends when a cell begins to divide.
Division Stage
Two phases of cell division:1.Mitosis
- the contents of the nucleus separate into 2 identical copies.
2. Cytokinesis- cytoplasm and organelles divide into 2 identical, separate copies- each cell now starts its own cell cycle
Cell Division - It’s Important
Through cell division livings things undergo three important functions:i) growthii) maintenanceiii) repair
ClassworkText• p 23 LC #1-3• p 25 LC #1-3• p 27 LC #1,3
Quiz: Next class on section (1.1) - cell parts, diffusion and osmosis