Transcript (1.2) Cell Division (p22-27)

(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 Division
When a cell divides
- two new cells are
created
- each cell is identical to
the original cell
The 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!
Chromatin
DNA
Cell Cycle
• The series of events in the
life of a cell is called the cell
cycle.
• Two main stages:
i) growth - called interphase
ii) 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) growth
ii) maintenance
iii) repair
Classwork
Text
• 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