Mini Exam Ch. 8pt2, Ch.9, start of pt.3 Flashcards
what is the role of goosecoid? what releases it? what activates it’s release?
blocks BMPs (skin formation)
- released by Spemann’s Organizer
- activated by Nodal
describe find it, move it, lose it with goosecoid
find it
- found through in situ hybridization
- in the dorsal blastopore lip (makes dorsal side and NS)
move it
- move it by grafting
- led to two spinal cords
lose it
- didn’t form a NS or archenteron
what are secreted proteins turned on by?
Nuclear proteins (all found in organizer)
- goosecoid
- twin, siamois
what are some examples of secreted proteins?
- Chordin
- Frzb
- Noggin
- Sonic Hedgehog
- Nodal-releated proteins (Continues to make nodal, even though goosecoid was activated by it_
- Dickkopf (thick head)
- Cerberus (mutliple heads)
where are E-Cadherins found?
epidermis (skin cells)
what is the main secreted protein turned on my goosecoid? describe what it does
Chordin
- turned on by IMZ cells
- binds directly to BMPs to inactivate it
- RESCUE ectodermal cells from epidermal (skin) fate by blocking BMP (does not induce NS)
what do BMPs do?
Induce skin to form in ectoderm
what is the default pathway of the ectoderm?
- naturally defaults to neural tissue!
- occurs when ectoderm receives no BMP signals
what happens when Chordin is blocked?
no NS
what is Otto Mangold (1933) known for?
Grafting experimenter #4
- created the idea Einstuckung
- organizer does region-specific induction
describe what happened when Otto took a late gastrula (already has NS & has migrated) and put different parts of the archenteron into the blastocoel of an early gastrula
Tissue gives rise to an extra part of the embryo depending on what section of the archenteron he placed there
described how Otto proved that the head is induced before the tail
- dorsal blastopore lips from early gastrula were transplanted into other early gastrula, they formed secondary heads
- dorsal lips from later gastrula were transplanted into early gastrula, they induced the formation of secondary tails
what does activation of BMP and Wnt make?
epidermis
Block BMP, activate Wnt
Posterior portion of NS
(Trunk & spinal cord)
Block BMP, Block Wnt
Anterior portion of NS
(Head & brain)
what types of things can block Wnt?
- Dickkopf
- Cerberus
- Frzb (soluble receptor, does not have the internal part of the protein)
- IGF
what does Retinoic Acid activate?
Wnt, Fgf, Shh
how are the right and left sides of an amphibian created?
Microtubules lean towards one side
- Vg1, Nodal (Xnr1) preferentially in the embryo’s left side
- Pitx2 (turned on by nodal) only on left side
what is an amniote?
- things that have an amniotic sac (chickens, reptiles, birds)
- tetrapods
- adaptation to lay eggs on land rather than in the water
- Laid as eggs or carried by the females
- Protected and aided by several extensive MBs
- lack the larval stage
what is the Chorioaliantoic MB (CAM)?
- Similar to a placenta, but in chicks!
- Allows for gas exchange, waste to be removed, CO2 out, O2 in
- Keep the embryo protected
what is Hensen node’s function?
dorsal blastopore lip
- Where cells move in to form layers
- Does the migration of cells inside to become mesoderm & induce other things to become NS
what is different about the chick embryo’s shape?
- Embryo grows as a disc (stuffed crust pizza)
- Not a big blastocoel cavity, very flat instead
- Only cells from the top migrate inward, then move out and up (mesoderm cells)
what are the two main layers in a chick embryo?
Epiblast: top
Hypoblast: bottom
what differentiates the chicks left and right sides?
- Shh, Cerberus, Nodal are found on both sides (right and left) but they are found more on the left side
- Pitx2 is only on the left side! (not the right)
describe the pathway on the left side that activates Pitx2
- Little bit more Shh on the left side turns on Cerberus
- Cerberus blocks the inhibitor of nodal -> BMP
- indirectly turns on Nodal
- Nodal turns on Pitx2
- DOUBLE NEGATIVE GATE
what are the negatives to using mammals as model organisms?
- Ethical considerations
- Smallest eggs (1/1000th volume)
- Eggs hard to manipulate (grafting)
- Low production (Less than 10 babies per litter/ovulation)
-Internal fertilization / development (Difficult on the mother) - Slow development (24 hours for the first cleavage)
- Long time to study generations
- Asynchronous divisions (Cells don’t divide at the same time or at the same rate_
- Genome activation (MBT) after 2nd division, not 12th division (Hard to piece out maternal effects)
positives to using mice and model organisms?
- Easy to breed
- Easily housed (Smaller organism, Less expensive)
- Large litters
- Shorter generation time
what day is the first division in mammals?
day 1
what day is the morula developed in mammals?
day 4 (uneven cells!)
what day do the cells enter the uterus?
day 5
what day is the hollow cyst developed?
day 6
what happens on day 7?
implantation into the uterus (endometrium)
what happens on day 9?
reaction of egg with mother
what day does gastrulation start?
day 14-16
what weeks is organogenesis?
weeks 3-8
when is neurulation?
week 3 (day 21)
what type of cleavage do mammals have?
rotational cleavage
what division are the cells compacted you can no longer see each individual cell (morula)?
4th division
what is the cell called when they are no longer totipotent?
blastula
what are the two distinct things in the embryo?
trophoblast (placenta)
inner cell mass (embryo, MBs, amniotic sac)
what does the Oct4 signal do?
you can do anything -> pluripotency signal
- Expressed in the morula and ICM
- Blocks trophoblastic fate
- Stem cell signal
- Remain undifferentiated
what are the steps of implantation?
- Egg releases proteolytic enzymes to crew up zona pellucida (similar process as acrosome rxn in sperm) as it enters uterus -> contacts mother’s cells
- Embryo embeds into mother (proteolytic enzymes, polysaccharides, ECM proteins, hyalin-related proteins)
- inner cell mass divides into two layers (epiblast, hypoblast)
- Mother’s blood vessels (Trophoblastic lacunae) form around the embryo, but never directly connects (Molecules diffuse over to baby)
what is the difference between the epiblast and hypoblast?
Epiblast: becomes mesoderm, endoderm, ectoderm (embryo and amniotic ectoderm)
Hypoblast: becomes a supportive layer of cells (nutrients, yolk sac)
describe how O2 is delivered to the baby from the mother
- Goes through the Chorion (made by trophoblast cells_
- Allows for an area of transfer of nutrients between mom and baby where the mom and baby blood vessels never have to touch (diffusion)
- Baby picks up the oxygen from mom’s blood
how many arteries and veins are in the umbilical cord?
2 arteries
1 vein
what is the function of the allantois
gets rid of nitrogenous waste, given to mom to get rid of
what are monozygotic twins?
Identical Twins
- one sperm, one egg
what are the three different ways monozygotic twins are developed?
- blastomeres separate before blastula forms (splitting b/w days 0-5days)
- ICMs separate before amniotic cavity forms (splitting b/w days 5-9 days)
- The node separates before gastrulation (after day 9)
describe how the development of identical twins when they split before blastula forms
- two cells (24 hours, first division) pull so far apart from each other they are no longer attached
- regulative development (each embryo continue to divide to form their own embryo)
- Forms 2 chorions (2 implantations), 2 amnions
describe how the development of identical twins when they split before amniotic cavity forms
- Implantation is starting to occur at this point in time
- One large blastula plants into mother, inner cell masses separate from each other, before amniotic cavity forms
- One chorion (one implantation), 2 amnions
describe how the development of identical twins when they split right before gastrulation
- After amniotic cavity has formed, cells didn’t divide equally (2 NS, primitive streaks move away from eachother)
- 1 chorion, 1 amnion
what are dizygotic twins?
Fraternal Twins
- two sperm, two eggs
what are Chimeras (un-Twins)?
- Two mouse embryos at early cleavage stage (before morula)
- both release enzymes that chew up the zona pellucida
- the two embryos stick to each other and then implant into mother (Cells are still totipotent!)
- Creates one animal that is mixed (almost looks like a calico mouse)
- Regulative/Conditional specification (dependent on neighbors)
are anterior or posterior hox genes dominant?
posterior hox genes!
describe the difference in naming of hox genes between mice, humans, and flies
HOX (humans)
Hox (mice)
Hom-C (flies)
how does having chromosome duplications positively impact hox genes in mammals compared to flies with only four chromosomes?
- Having more copies allows the animal have a better address for development
- Subsequent deletions (We have so many copies that when they get deleted, its okay)
what are Paralogous groups of hox genes?
Same gene family, except they have a different location
- A1, B1, C1, D1 (all on different chormosmes, but all most anterior)
describe find it, move it, lose it with hox genes
Knockouts (lose it)
-Remove a hox gene
- Double of what is anterior of the removed gene
Retinoic Acid (move it)
- Turns on hox genes
- Move hox gene by changing amount of RA
Comparative anatomy (find it)
- Chicken vs mice
- Looking at their anatomy and the hox genes that are different
describe the hox gene lose it experiment
- Looked at mutants in hox genes and see what happened to their vertebra
Knocking out all versions of hox10 (hox10a, 10b, 10c, etc.)
- lost all parts of lumbar region
- created more thoracic vertebrae instead
- more anterior structure (thoracic) duplicated itself in the area that the hox was lost
- anteriorizes lumbar
Knocking out hox11
- Didn’t create a sacral region
- lumbar region was created instead (more anterior structure)
- anteriorizes sacral
describe the hox gene move it experiment
Extra RA
- makes more cervical vertebrae
- The regions are expressed in a broader area
- Removes the more anterior region (opposite of lose it)
- posteriorizes C1 into C2
Less RA
- More posterior thing is deleted due to the more anterior region getting less RA
- Lose more posterior structures (similar to lose it)
describe the hox gene find it experiment
- Compare where we know a certain hox gene is expressed vs what it actually looks like
- Chick -> 14 cervical, 7 thoracic, 12 lumbo-sacral, 5 coccygeal
- Mice -> 7 cervical, 13 thoracic, 6 lumbar, 4 sacral
- LOOKING AT the cervical regions of both animals
- Hox 5 in a chick creates cervical region (14 somites)
- Hox 5 in a mouse creates half as many cervical region (7 somites)
- Hox 5 is the border between cervical and thoracic spine
what happens when you add retinoic acid to an amputate axolotl limb?
the hox genes tell it that it’s more proximal than it actually is, so it creates a shoulder -> arm -> wrist -> hand
- it should’ve only created the hand
describe how Accutane leads to birth defects
- Contains high doses of RA
Babies couldn’t express hox genes correctly, addresses were all wrong - led to majority of cases either miscarrying or having birth defects
describe how megadoses of Vitamin A can lead to birth defects
Vitamin A is converted into RA
what is a stem cell?
Cells that are able to still differentiate
- No longer a stem cell when they are finalized in a specific shape etc. that no longer divide
what is the hierarchy of differentiation when it comes to stem cells?
- Totipotent (can become anything even extracellular parts: germ line cells, all cells in the morula)
- Pluripotent (can still become a specific layer, almost all options)
- Multipotient
- Limited differentiation potential
- Limited division potential
- Functional non mitotic neuron
