Chapter 8 – Cellular Reproduction. In order for organisms to grow and reproduce, cells must divide.
The Cell Cycle Chapter 10, Section 2. Why do cells divide? §For growth, repair, and reproduction.
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Transcript of The Cell Cycle Chapter 10, Section 2. Why do cells divide? §For growth, repair, and reproduction.
The Cell Cycle
Chapter 10, Section 2
Why do cells divide?
For growth, repair, and reproduction
When do cells divide?
Most limiting factor in size is the size of the cell membrane.
A cell has to stay small so that all the things that need to go in and out don’t have too far to travel. The surface area to volume ratio must be small so cells stay tiny and divide instead of growing too big.
How Do Cells Divide?Cell cycle - sequence of phases
in the life cycle of the cell
Interphase3 parts: G1, S and G2
G1 - cell growth; make new organellesS – DNA replicationG2 – short; organelles for cell
division are produced
What is Mitosis?The process whereby body
cells(somatic) are made by cell division
How does it work?
4 Stages
1st - Prophase
Chromosomes become visibleCentrioles go to opposite sidesSpindle fibers formNuclear membrane breaks down
-2- Metaphase- Chromosomes line up along the equator in pairs-3- Anaphase- Chromosomes
move to opposite ends of the cell-4- Telophase- a cleavage
furrow forms and…each cell now has exactly the
same number of chromosomes!
Cytokinesis
Cytoplasm pinches in half
Mitosis
Results in an exact duplicate of the same cell. There is no change.
Interphase
Prophase
Metaphase
Anaphase
Telophase
MEIOSISChapter 11
So, What is Meiosis?
The process whereby gametes or, sex cells are made by cell divisionExamples are sperm & eggs
only!
How does it work? 8 Stages Prophase I
(includes chromosomes crossing over and exchange)
Metaphase IAnaphase ITelophase I
Prophase IIMetaphase IIAnaphase IITelophase II
The same things occur with chromosomes except the number of chromosomes is halved
Meiosis results in cells that have only 23 chromosomes in humansMen make 4 sperm cellsWomen make 1 egg and 3
polar bodies (which are excreted as waste products
Why is meiosis so important?
It provides for genetic variation crossing over occurs in
prophase I and IIshuffling of chromosomes
(or genetic information)
Mitosis MeiosisBody cells/
somatic cells4 Stages 1 divisionResults in 2
daughter cellsAsexual Growth2n - diploid
Sex cells / gametes8 stages 2 divisionsResults in 4 sperm or 1
egg & 3 polar bodiesSexual reproductionCrossing over – prophase I
1n - haploid