Transcript THE BIRTH OF CELLS - University of Central Oklahoma

CELL BIRTH
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Section 22.1
Grace Githunguri
BIRTH OF CELLS
Cell division
 Stem cells
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 Properties
 Tissue
maintenance
Embryonic stem cells
 Cell Fate
 Cell lineage
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 C.
elegans
Cell Division
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Symmetric
The progeny do not change their properties (same).
 Differences arise when cells diverge by receiving
distinct developmental or environmental signals.
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Asymmetric
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Size, shape, and/or composition, or genes may differ
in their state of activity.
Internal signals confer different fates on cells.
Stem cells- properties
Divides symmetrically
 Produce themselves indefinitely (Self
renewing).
2. Asymmetric division generates an identical
copy and a stem cell with restricted
capabilities.
1.
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Pluripotent (Multipotent) – Generate a number
of different cell types, but not all e.g. blood cells.
Unipotent – Forms a copy of itself
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forms one cell type.
Stem cells
Stem cells
 Totipotent
–generate all the cells types of
the body e.g Zygote.
 Zygote and neuron-glial cell precursor
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are not stem cells because they are incapable of self
renewing.
Embryonic stem cells
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Human Embryonic cells can be grown in
Suspension Culture and in Solid culture.
 Suspension
Culture
 ES
cells differentiate into multicellular aggregates
(embryoid bodies).
 Solid
Medium
 They
grow into confluent cell sheets with
differentiated cell types.
 ES
can also be induced to differentiate into
precursors for various types of blood cells.
Embryonic stem cells cont…
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Treatment of
Parkinson’s
disease
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Culture grown
neurons that
produce
dopamine.
Other conditions
like Alzheimer’s
disease.
Stem cells
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Differentiated cells have a shorter life span than that of
an organism.
They are replenished from nearby stem cell populations.
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Skin – epidermis
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Epithelial lining of the small intestine.
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Underlain by a layer of stem cells that give rise to more layers and
keratinocytes.
Regenerated from deep intestinal wall in pits called crypts.
Plant stem cells
 Persist for life in the meristem.
Stem cells
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Production of new cells is
controlled.
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By specific signals e.g -
catenin
Overproduction leads to
excess proliferation of the
intestinal lining.
 Links certain cell-cell
junctions to the cytoskeleton
 Signal transducer in the Wnt
pathway.
 Moves cells from epidermis to
hair cell fates.
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Cell Fate.
Restricted during development.
1.
Gastrulation form germ
layers;
Ectoderm
 Mesoderm
 Endoderm
cell populations with
different fates.
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2.
Germ line
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Stem cells and precursor
cells that give rise to eggs
and sperm.
They have reduced number
of replications.
Cell lineage
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Are identical in all individual of a species because Cell
are under tight genetic control.
Signals can direct identical cells to different fates.
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C. elegans produce six different founder cells.
Cell lineage
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Genetic control of cell linage come from
heterochronic mutants.
 Too
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early (precocious development)
 Too late (retarded development).
Too early e.g C. elegans
Mutation of lin-14 leads to premature formation of PDNB
neuroblast.
Prevent L2-type cell division.
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lin-14 and lin-7 are micro RNAs that serves as timers of gene
expressions.
Control translation of mRNAs by hybridizing them.
Summary
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Cell Divide
 Symmetrically
 Asymmetrically
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Pluripotent stem cells
 More than one type of cells
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Cultured Embryonic stem cells
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Stem cells
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Are controlled from
differentiating by specific
signals.
Persist for life in the meristem.
During development
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Differentiated cell types
Regenerate tissue cells
Plant stem cells
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precursor cells are restricted
in number of cell type they
form.
Animal development
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Germ layers- Ectoderm,
Mesoderm and Endoderm
Population of stem cells
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C.elegans
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Germ line- eggs or sperm
Asymmetric division of zygote
Short regulatory RNAs
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Control timing of
developmental division.