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Growth and Division of the Cell (Phases mitosis mitosis (Prophase…
Growth and Division of the Cell
Concepts
Stages of initiation
Growth
Death
Cell cycle
Death
Not really death if the divide
Growth
Reproduction
Division
Common
About 25 million divisions per second
Cell cycle arrest
Final form stops dividing
Enter extended growth period
Differentiate and mature
Growth Phase of the cell cycle
G1 Phase
Happens in
interphase
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First stage after division
Cell recovering from division
Conducting normal metabolism
Synthesis of nucleotides
Used for next DNA
Cell cycle varies
Several hours to months
Longest cell cycle phase
S phase
Synthesis phase
Genes and DNA in nucleus are replicated
Duplicate molecules remain attached at centromere
Chromosome
Genes attached in a linear structure
Double chromosome
Two chromosomes stuck together
By cohesion
Histones
Gives DNA protection and structure
Centromere
Located near center of chromosome
Most plant cells enter S Phase
Happens in interphase
G2 Phase
After S Phase
Cells prepare for division
Lasts about 3-5 hours
Cell produces proteins for processing chromosomes
Breaks down nuclear envelope
Factors located in cytoplasm
Happens in interphase
Division Phase of the cell cycle
Mitosis
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Duplicate division
Nuclear genes are first copied
One set of genes separated from the other
Each are packed into their own nucleus
More common type of karyokinesis
Method of cell replication in multicellular organisms
Eukaryotic unicellular organisms
Used when not going through sexual reproduction
Produces new nueclei
Exact copies of orignal
Occasional error
Has 5-7 steps
Cytokinesis
Division of protoplast in two
Each half has elements from original
Not necessary for exactly half of each
Formation of phragmoplast in plants
Meiosis
Sex Cell division (gametes)
Two come together and form zygote
Zygote grows into adult
Meiosis I
Contains
Prophase I
Metaphase I
Anaphase I
Telophase I
Meiosis II
Splits like mitosis
Each daughter cells is haploid
Phases
mitosis
Interphase
DNA of chromosome
Long extended double helix
First in order
Prophase
Second in order
Chromosome condense
Chromosomes become shorter and thicker
Happens multiple times until ~ 2-5micrometers long
Can be moved around cell more easily
Nucleolus becomes less distinct
Usually disappears
Nuclear envelope breaks
Daughter cells move toward opposite ends of cell
Metaphase
3rd in order
No distinct boundary between prophase and metaphase
Chromosomes align in center at metephase plate
Number of chromosomes is doubled
Anaphase
4th in order
Begins after cohesion releases centromeres
Depolymerization happens at the ends
Pulls daughter cells away from twins
Telophase
5th in order
Fragments of nuclear envelope appear at ends
Chromosomes uncool and become less distinct
Spindle disappears
Most events are reversals of prophase
Less Common Types of Division in Plants
Karyokinesis occurs without cytokinesis
Multinucleate cells are formed
Coenocyte
Cell with hundreds or thousands of nuclei
Cell division without nuclear division
Most common in
Algae
Fungi
Nutritive tissues of seeds
Cells become multinucleate
New walls form around each nucleus
Cell division in algae
Nuclei
Virtually identical to animals
Cytokinesis
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Cell division of prokaryotes
Meiosis does not occur
Cytokinesis is very simple
Process of infurrowing
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Membrane pulls forward and punches in two
Division of chloroplasts and mitochondria
Similar to prokaryotes
Contain circles of naked DNA
Separated by membrane growth
Division by infurrowing
