Transcript Cellular Mechanisms of Developement

Cellular Mechanisms of
Development
Chapter 19
Developement
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Growth (cell division)
Differentiation
Pattern Formation
Morphogenesis
Cell Division
• CDK’s control Cell cycle
• Cleavage
– Blastomeres
– No G Phase in early cell division
C.elegans
Stem Cells
• Tissue specific Stem cells
• Totipotent
• Plouripotent
Blastocyst
• Embryonic Stem Cells
Do plants have Stem Cells?
Cell Differentiation
• First Cell Determination Occurs
– Humans have 210 types of cells
• Proteins, morphologies, and functions help us tell
them apart
How can we tell if something is
Determined?
• Do an experiment
– Transplant cells and see what they become
– Figure 19.5
Molecular Basis of Determination
• Use transcription factors to change
patterns of gene expression.
• Cells become committed to a particular
developmental pathway in two ways– Cytoplasmic determinants from the parents
– Cell-cell interactions
Induction
• Animal and Vegetal pole interactions
• Fibroblast growth Factor (FGF)
Reversal of Determination
• Experiments showed that single cells from
fully differentiated plants could develop
into mature plants
• What about animals?
– Frog Experiments
– Mammals
Dolly
Steps to cloning Dolly
• 1. Cell containing source DNA was grown
on a medium to stop the cell cycle
• 2. Eggs obtained from the ewe were
enucleated
• 3.Somatic Cell Nuclear transfer (SCNT)
• 29 of 277 fused couplettes formed into
embryos and were implanted into
surrogate mother
• 1 lamb was born 5 months later
Problems with Reproductive
Cloning
• Low Success Rates
• Large offspring Syndrome
• Develop age related disorders very early
– Why
• Lack of Imprinting
Therapeutic Cloning
Stem Cell Research Debate
• What do you think?
The future of Stem Cells
• Adult stem cells may offer an alternative to
ES cells
Body Axis
Pattern Formation
• Determines that is going to develop where
• Maternally Determined
Prefertilization
Postfertilization
Syncytialblastoderm
Cellular Blastoderm
Segmented Embryo
Anterior-Posterior Axis
• Bicoid and Nanos protein gradients
• Hunchback and Caudal maternal
messengers
– Found evenly throughout the egg
Dorsal- Ventral Axis
• Gurken and Dorsal Proteins
– Not what you would expect
Segmentation Genes
• Gap Genes- map out the most basic
subdivisions of the embryo
• Pair-rule genes- subdivide the segments
made by the gap genes ( ex hairy)
• Segment Polarity Genes- subdidived
segments made by P-r genes (ex
engrailed)
Homeotic Genes
• Give each segment an identity
– Awesome mutations- Untrabithorax and
Antennapedia
Homeotic Gene Complexes
• Bithroax Complex
• Antennapedia complex
– HOX genes- refers to all homeobox
containing genes that determine the identity of
a body part
– Order of homeobox gene corrosponds to body
segment
Plants
• Do not have Hox genes have Mads-box
gene
Morphogenesis
• Ordered form and structure
• Regulated in 5 ways
– Number, timing, and orientation of cell
divisions
– Cell growth and expansion
– Changes in cell shape
– Cell migration
– Cell death
Cell division and Unequal
cytokinesis
• This allows cells to be different sizes
Cell death
• Apoptosis vs Necrosis
• When does apoptosis happen?
Cell Migration
• Does not happen in Plants
• Achieved by Cadherins and Integrins
Plants
• Plane of cell division determines
morphogenesis
– Smaller cell becomes embryo while larger
becomes suspensor
– Words to know for AP test Cotyledons and
Apical Meristem
Environmental Effects
• Some Obvious
– Jack Pines
– Dormant Seeds
• Some not so Obvious
– Thalidomide
TSD
• Why is this important? Why now more
than in the past?
Endocrine Disrupters
• DDT
• DES
Tissue Development