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138 Lectures 1-10
Terms in this set (60)
What experiments showed that all cells have the same genetic material?
Blastomere isolation - at early stages, cells will grow into whole organisms
Nuclear transplant - adult nucleus into egg=clone
Fate map vs. Genetic screen
Fate map is dyeing cells to see where their progenitors are
Genetic screens are mutating random shit to get a good phenotype
What factors go into considering a model organism?
Cost to maintain, progeny number, generation length, genetic tools, genome size
In which organisms are germ cells also stem cells?
Nonmammals = both egg and sperm germ cells
Mammals = only sperm germ cells
Which species have cytoplasmic determinants?
Frogs, worms, flies
How does sex cell production go?
-gonia (2n) undergoes replication to make a primary -cyte (4n)
primary -cyte undergoes meiosis I to become a secondary -cyte (2n)
secondary -cyte undergoes meiosis II to become ovum/sperm (1n)
What is yolk? What makes it?
A phospholipoprotein that functions as an energy source
Made in the liver
What do fly egg follicle cells do?
Signaling and making egg shell
What experiment showed the existence of cytoplasmic determinants?
Enucleate fertilized sea urchin egg and it can develop to an arrested blastomere
What happens if you block protein synthesis in a fertilized egg?
You get NO development, protein synthesis is necessary
How are maternal mRNAs stabilized and not transcribed until fertilization?
Both are done by proteins that bind the 3' UTR
What is imprinting and what experiment showed it?
Embryo will only express certain genes from maternal or paternal chromosome via DIFFERENTIAL METHYLATION, shown by embryos artificially created with two male or female genomes not being able to make embryo or placenta, respectively.
How is acrosome reaction activated?
Ca INFLUX that allows fusion of the egg and sperm membranes
How does the fast block to polyspermy work?
Transient egg membrane depolarization due to Na influx and K efflux (ONLY FROG AND URCHIN)
How does the slow block to polyspermy work? What causes it?
Permanent release of coritical granules into vitalleine layer due to Ca release from the ER
What do cortical granules contain/do?
Enzymes and polysaccharides to raise vitalleine layer, harden outer coat, and remove sperm-binding proteins from the egg membrane
How do we know the slow block to polyspermy is due to Ca?
Ca ionophore activates it,
Ca chelator prevents it
What activates the egg after sperm entry?
Rise in free intracellular Ca - turns on transcription, translation, metabolism, and cleavage machinery
What factors can affect division patterns?
Centrosome position in metaphase
Yolk distribution in whole embryo
Do mammals have yolk? Do they have full or superficial early divisions? Do they have a blastocyst or blastoderm?
No yolk, full divisions, blastocyst
What factors allow compaction to induce differentiation?
Cytoskeletal distribution changes, which means that later divisions give cells different parts of the cytoskeleton and changes the planes of division.
What triggers the Maternal to Zygotic Transition?
Increasing ratio of DNA:cytoplasm
How is chromatin demethylated in reproduction?
Fertilization causes massive demethylation
What can cause determination?
1. + feedback loops that no longer need an external signal to sustain
2. epigenetic changes
What can cause mRNA localization?
1. transport by MT's
2. degradation in specific areas
Techniques to find genes in a sample (presence or specific location)
FISH for location
Microarray or RNA seq for presence
Techniques to find gene function?
RNAi or genetic screen
Transgenics (stem cells and inject)
Transgenics using reporter to find loc (oskar with bcd reporter)
CRISPER or Cre-lox
What can cleavage do to induce differentiation? (3)
Change cell-cell interactions
What experiment showed maternal determinants?
Cutting across animal-vegetal axis at 8-cell stage animalizes or vegetalizes the halves
What fly factors make germ cells?
Posterior maternal determinants that induce follicle cells to become polar granules - irradiating posterior end causes no fertility
What do bcd and nanos do to Hb expression?
bcd activates TS
nanos represses TL
therefore Hb mRNA is everywhere in embryo
Not all ________ are ___________
Cytoplasmic determinants are not all Maternal effect genes
How does the fly egg get stuff from the nurse cells?
MTOC that reaches MTs into nurse cells
How are follicle cells established on A/P axis?
Signaling from older egg chambers
How does the future ovum get ID'd on the posterior of the fly egg?
Signaling from older egg chambers
What final step in Drosophila A/P axis establishment does Gurken/Torpedo signaling do?
MT rearrangement that also puts maternal mRNAs (bcd, nanos, torso) to different parts of the oocyte
What ventral cells make Spatzle?
Ventral Follicle cells
How is Sog activated?
Activated by low Dpp levels
How is Dpp activated?
Dpp activators are present throughout embryo, only DORSAL-expressing ventral cells repress it
What is the function of Tolloid?
It cleaves Sog, which itself stops Dpp activity, so Tolloid activates Dpp
What is special about Dpp and Twist?
They are ZYGOTIC GENES YAAAAAAAAAAY (also Dpp is secreted)
What are the vertebrate analogs of Dpp and Sog?
Are GPS genes maternal or zygotic?
What is the phenotype of loss for GPS genes separately?
Gap genes: expressed earliest, lose many parasegments
Pair-rule genes: expressed next, lose parts of every other parasegment
Segment-polarity genes: expressed latest, lose smaller parts of every segment
Gap genes - area of expression? Controlled by what?
Wide band along embryo A/P axis
Controlled by maternal genes and each other
Pair-rule genes - area of expression? Examples? Controlled how? Effect on A/P axis?
Expressed in alternating parasegments (14 in total)
Eg eve and ftz
Each has enhancers that bind different maternal and gap genes, eg eve activated by bcd and Hb, repressed by Giant and Kr - ID indiv enhancer regions by putting them in front of reporters/mutate indiv regions
NO EFFECT ON A/P AXIS
Segment-polarity genes - function? Area of expression? Examples?
Define A/P axis within parasegments, so define eventual cell polarity
Expressed at edges of parasegments
Hh and Wg make + feedback loop, initially activated by ftz and eve
What does "colinearity" mean? What is its mechanism?
Hox genes are expressed 3' to 5'
Temporally: 3' genes are expressed earlier
Spatially: 3' genes are expressed in more anterior parts of the embryo
This occurs through chromatin modifications that open the DNA in this order
How is Hox gene expression refined?
miRNAs and more posterior Hox genes will repress activity of any single Hox gene
Epithelial vs Mesenchymal MF's?
Epithelial: Apical belt and longitudinal fibers
Mesenchyme: Stress fibers
What does the cell use to properly undergo convergent extension?
Adherins and planar cell polarity
Epiboly - function? Methods to do it?
Combine cell layers, eg to cover vegetal part of embryo
Done by cell flattening or radial intercalation (both use adherins junctions)
What follows involution in frogs?
Convergent extension of cells through the involuted divet, puts endoderm and mesoderm under ectoderm
What are VegT and Vg1? Knockout effects?
ZYGOTIC GENES that specify vegetal pole
MO = only get ectoderm, therefore important for endoderm (and by inductive effects, mesoderm)
Which part of the embryo does the mesoderm originate from? Experiment?
Animal cells, dyed animal cap cells became mesoderm when induced by vegetal cells in co-culture
What initial factor decides D/V axis in frogs? How does this occur?
Sperm entry, which triggers cortical rotation and puts dorsal factors (B-catenin) on opposite side of the embryo
MT's move factors, KO MT's = no cortical rotation
Nieuwkoop center - how it's established, what it specifies and how
Established at dorsal vegetal endoderm by VegT/Vg1 and B-catenin overlap
Specifies overlying mesoderm to be dorsal Spemann Organizer via a (dorsal to ventral) Nodal (Xnr) gradient
Experiments that showed effects of Nodal?
Use dominant negative Nodal receptor, which ventralizes the whole embryo
Beads soaked with different amounts caused different structures, so its a morphogen
What does the Spemann Organizer make?
Chordin/noggin/follistatin to block BMP
What do BMP and Dpp have in common?
Thought BMP ventralizes and Dpp dorsalizes, both suppress neural fates (frog neural = ventral ectoderm, mammal and bird neural = dorsal ectoderm)
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