Chromosome

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THE CELL
CYCLE
Overview
• Complex process
• Eukaryotic cells
• All cells divide at
different rates
(muscles v skin)
• Must replicate
perfectly for
– Growth
– Repair
Overview
• Creates two identical
daughter cells from a
parent cell (46
chromosomes each)
• Happens in body cells
(somatic cells)
3 Distinct Periods
• Interphase
• Mitosis
• Cytokinesis
Description of Each Stage
• Interphase
• Longest Stage
• Three Phases
– G1 = cell growth and
development/ doing it
job
– S = DNA replicates
– G2 = additional growth
– Genetic Material now
in chromatin form
DNA Chromosome
• Start w/ DNA
• Wind around histones
• Condenses to form
chromatin
• Chromatin condenses
to form chromosomes
– Made of two sister
chromatids
Labeled Chromosome
Mitosis
• 4 Phases
–
–
–
–
Prophase
Metaphase
Anaphase
Telophase
* Must know what is
happening with the
chromosomes at each
phase
Animated Mitosis Cycle
http://www.cellsalive.com/mitosis.htm
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Prophase Details
Prophase
• Chromatin condenses
and becomes visible =
chromosomes
• Nuclear membrane
dissolves
• Spindle fibers form
• Centrioles separate
Animal Cell
Plant Cell
Spindle fibers
Centrioles
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Metaphase Details
• Chromosomes line up
down center of cell
• Attach to spindle
fibers
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Anaphase Details
• Sister chromatids
separate
• Spindle fibers shorten
to move chromatids to
opposite sides of cell
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Telophase Details
• Chromosomes are
now split and in two
almost new nuclei
• Chromosomes uncoil
to chromatin
• Nuclear envelope
reforms
• Fibers disappear
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Cytokinesis
• The cytoplasm splits
and 2 new cells are
formed
• Daughter cells
IDENTICAL to original
Meiosis
• A double division to
produce sex cells with
half the number of
chromosomes- one
copy of each gene
• Mixes genes through
independent
assortment and
crossing over to gain
variety!
• Humans-23
chromosomes in
each egg or
sperm cell
(gamete)
Independent
Assortment-
Crossing Over
“Putting It All Together” - Fertilization
Mitosis
Number of divisions
Number of
daughter cells
Genetically
identical?
Chromosome #
Where
When
Role
Meiosis
Using the above example as a layout-Create
a neat chart showing the differences
between mitosis and meiosis.
Mitosis
Meiosis
2
Number of divisions
1
Number of
daughter cells
2
4
Yes
No
Same as parent
Half of parent
Where
Somatic cells
Germ cells- gametes
When
Throughout life
At sexual maturity
Growth and repair
Sexual reproduction
Genetically
identical?
Chromosome #
Role