Transcript Cell Division

How do little elephants grow up to be BIG
elephants?
Cell Division
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Large cells cannot
transport nutrients across
membrane
Cells will divide when
they become too large
Old cells that become
damaged must be
replaced
Each new cell must be an
exact copy of the original
Cells are the basic unit of
structure & function of all
living things…
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If all living things are made of cells,
what makes each organism different
from other organisms?
Human sperm Cell fertilizing egg
Sea Urchin sperm cells fertilizing egg
DNA
(deoxyribonucleic acid)
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Contains the genetic
instructions used in
the development and
functioning of all
known living
organisms
Chromosomes
Compacted DNA containing cell’s
genetic code
 DNA must compact in order to
separate when cells divide
 Each chromosome has a matching pair
(Homologous Pair)
 One came from your mom & one came
from your dad
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Three Phases of Cell Division
Interphase – cell copies DNA and
prepares for division
 Mitosis – chromosomes line up in
middle of cell then separate
 Cytokinesis – cytoplasm divides
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Interphase
Cell growth
 Chromosomes
are copied
 Chromosomes
appear as
threadlike coils
(chromatin)
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Mitosis = nuclear division
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The steps of mitosis ensure that each
new cell has the exact same number of
chromosomes as the original
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Mitosis is divided into 4 phases
PMAT
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Prophase: DNA condenses (coils)
into chromosomes
- copies of each chromosome stay
connected
- now called sister chromatids
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Metaphase: chromosomes move
to the center of the cell
-spindle fibers help them align
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Anaphase: sister chromatids
separate & move to opposite ends
of the cell (spindle fibers pull apart)
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Telophase: chromosomes begin to
uncoil and form two new nuclei
Animal Cell
Plant Cell
Cytokinesis
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Cell membrane moves inward to create two
new daughter cells
 each has its own nucleus with identical DNA
(chromosomes)
 The two new cells are genetically identical
Animal Cell
Plant Cell
Cell Cycle
Bacteria Cell Division
(Binary Fission)
Bacteria only has one
circular chromosome.
 The chromosome
replicates then the cell
divides in two.
 The two daughter cells
are identical to each
other.
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Viruses
infectious nonliving organism
that reproduces
within the cells of
an infected host.
 It is composed of
DNA inside a
protein coat or
capsid.
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