The wild imaginings of midterm content. Fill your soul

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1 The wild imaginings of midterm content. Fill your soul 1-2 Is the sperm activation the same as capacitation? sea urchin and mammal -- acrosomal reaction must occur. Acrosomal Reaction is sperm activation. Capacitation is the maturation of the sperm. Only Mature Sperm can fertilize the egg. Fertilization implies the acrosomal reaciton. Why is it important to prevent polyspermy? How is this done in the sea urchin? What would happen to the sea urchin egg if it became polyspermic? It is important to prevent polyspermy in order to allow successful reproduction to occur. Aneuploidy on the level of chromosome sets would not cause viable offspring or successful divisions. Polyspermy in a sea urchin (e.g. two sperm fertilization) would result in an incorrect number of sets of chromosomes (triploid) in the nucleus. Division would then be inconsistent in terms of genetic content (sets of chromosomes), aneuploidy would occur as a result of nondisjunction and would cause improper development, if it develops at all. Describe and distinguish between the fast block to polyspermy and the slow block to polyspermy. The fast block and slow block are adaptive reactions to fertilization that occur within seconds/minutes of fertilization to prevent polyspermy. The Fast Block involves a change in electrical potential (through hyperpolarizing and depolarizing means) on the cellular membrane of the egg and occurs within 1-3 seconds post fertilization and is transient (lasts ~1minute). The resting potential shifts from -70 (low Na + inside cell vs. high Na + in the sea water) to +20mv by influx of Na + ions. (Cl- ions can be used in some amphibians due to different environmental conditions). Because this is a transient change, the fast block functions as a delaying of polyspermy that allows the slow block to work for more permanent change. The Slow Block to polyspermy involves the cortical granule reaction and happens ~ 1 minutes post fertilization. This is accomplished by fusion of the cortical granules with the egg cell membrane releases contents into the space between the cell membrane and the vitelline envelope that modify the extracellular space. Proteins include Serine Protease (digests bindin receptors sperm is clipped off, digests protein holding the egg cell membrane to the vitelline envelope. Creates the fertilization envelope by fusion of components of the granule and the vitelline envelope. Mucopolysaccharides - create an osmotic gradient causing water to enter and expand the envelope and Peroxidase enzymes - harden the envelope by cross-linking tyrosine residues Finally, a hyalin coating is formed around the egg.

2 3-4 Is protein synthesis essential during early cleavage? Is mrna synthesis essential during early cleavage? During early cleavage, mrna synthesis is not vital due to the fact that the embryo relies on the maternal mrna, however protein synthesis is. The developing embryo translates the maternal mrna to produce proteins until the point that it reaches the maternal foetal transition of mrna synthesis. It does not transcribe its own DNA during early embryogenesis. At this point, the embryo synthesizes its own mrna, and mrna synthesis would be important. DNA is always used and synthesized for rapid cell division. Actinomycin D does not arrest early amphibian cleavage but blocks gastrulation. What sort of conclusions can you draw from this observation? -Actinomycin D is used by scientists as a transcription inhibitor, and was used in the water of Sea Urchins to determine if translation was occurring. Despite being a transcription inhibitor, in the experiment, it was found that translation and protein synthesis was happening due to Amino Acid consumption from the environment. This stopped/dropped to no activity with the addition of Actinomycin D (prevents transcription) indicating that the maternal mrna had run out. Without ACTD, translation occurs past this point as the embryo relies on its own zygotic mrna as it begins transcription of its own DNA, in sea urchins. In mammals (mice), this embryonic transfer occurs earlier on in development, 2 cell stage, 4 cell stage. Preventing transcription early on in the stage would halt development. What cellular structures are being most actively synthesized? Because of the very rapid cell divisions, the cell membrane structures are very actively synthesized. Additionally, cytoskeleton development and macro/micro filaments are also important. What is the difference between protostomes and deuterostomes? Most invertebrates develop as protostomes (sea elegans), first mouth, where the oral end of the animal develops first from the blastopore (spiral cleavage, determinant). Most vertebrates on the other hand, develop as deuterostomes, where the oral end of the animal is created from the second opening. The blastopore in deuterostomes becomes the anus, and that is what is first formed. Deuterostomes show indeterminate development, (each of the cells early on are capable of developing as complete organisms), radial cleavage. 3 types of cell specification

3 1. Autonomous Cell movements are irrelevant because the determination of what the cell should be is within the cell. Irrespective of movement, the cell 2. Conditional specification depends on cell movement, as it has to do with interactions and relative position between cells. Movement plays a role here as neighbouring cells influence the cell. 3. Syncytial is specification related to interactions between the cytoplasmic regions prior to cellularization of the blastoderm. Describe and give specific examples of how changes in cell adhesion and changes in the migratory properties of cells are important during early embryonic development. Cell migration for the purposes of location or structural changes is very important during development (e.g. neural crest cell migration, ingression, invagination, involution etc ). Adhesion and migratory properties help make this possible. During the epithetical to mesenchymal transition, Primary Mesenchyme loose affinity for the high layer and leave the vegetal pole. Becoming looser enables the epithelial to mesenchymal transition as it enables it to move. Attachment to neighbouring cells decrease, loosening junctions, change in shape that allows for the ability to migrate. 5-6 BICOID - the point where injected will be where the head will be formed, embryo with a head in the middle. Bicoid is the anterior determinant. - What if we inject the protein instead of the messenger RNA-- time wise, the protein would act faster, mrna cant diffuse, but protein can diffuse through the membrane. > mrna does not diffuse, protein does diffuse, therefore the protein has an effect on the caudal -- quicker, diffuses from the point of injection, broader. - bicoid is anterior determinant, caudal is posterior, we know caudal and bicoid distribution. - bicoid inhibits the caudal mrna TRANSLATOION, translation inhibitor - can also be transcription factor. What is the Grey Crescent? - There is no function of the grey crescent it is a landmark during development. - In frogs, it forms opposite the site of sperm entry when the cytoplasm shifts.

4 What is betacatonin, what is the role in early zenopause development. When did we mention betacatonin before, is the role isimilar or not? - β-catenin is a transcription factor activated by/part of the wnt signaling pathway Normally accumulates in vegetal cells fated to become endoderm and mesoderm The accumulation in large micromeres is autonomous. It establishes the endoderm and mesodermal areas. What is formed during the first segregation of cells within the ICM? How do we call this structure? Which part of the structure will develop into the embryo proper? - developes into epiblast and hypoblast, together called the bilaminar disc, edibles develop into, and extra embryonic ectoderm (amnionic ectoderm) GILBERT STATEMENTS - statement 1, statement 2, statemetn 3, statement 6, 8, 10, 12, 13, 16, and come up with your own examples. ** BONUS YEEE What is the blastocyst? - mammanilian blastula. characterisitc of division: low, uneven, compaction <**, zygotic embroyo gets transcribed earlier than in others. ect 9/10 What is the difference between primary and secondary neurulation? * Primary in anteriori, neuraltion of involt, invagination of ectoderm in the anterior art of th ebody, neural tube detacthces, mesenchyal, chord forms will be hallowed out, and then filled and then attachd. Where and how is the occlusion of the neural tube formed? What is the outcome of the temporary occlusion? Why is this happening? - to accumulate fluid pressure - it is not permamemnt? Why is the liquid coming in? Theories? How our brian is formed. Outline the experiment which showed the role of notochord as the d-v axis organizer. <-- lots of writing. Neural Crest Cells - how is it specified and differentiatied to particular neural system cells? Did we talk about somethign similar recently? --> Similar to the stem cells for blood cells, ability ot differentiate into different types of cells, based on basic environment. cytokines. Signals help them accquire aparticular faste. Migration of the neural crest cells, enables them to have all these different fates. TABLE * on middie or final. A cartilage of WHAT? not all catrilatinge nad bones are formed from neural crest cells. Process of ossificaiton?nerual crest cells are goin through -- intremembranous ossification. (endochronical ossifcaiton -- doesnt do.) : the cartilage precursor/model is happenign in endochrondrial. How do we group them? -- everything is about thier migration, and where do they pinch off, which part of the neural tube? Lect 11/12 How does protein Notch influence gene expression? (in general) - signalling, protein, communicate: when they connect, theres a change on the inside of the cell, and that influences gene expression. In the case of NOTCH, there is a chang einside of the cell,

5 nothc being cleaved off, and the cleaved notch in the cytoplasm goes into the nuclease and works as a transcirption factor. Ligand for notch - delta. Draw the relative geometric shapes -- on midterm or final Draw the relative geometric shapes and positions of the dermatome, sclerotome and two subdivisions of the myotome in respect to the notochord, neural tube, lateral plate mesoderm and overlaying epidermis. Why is this particular arrangement important? - they deper structures. ndt on structures surroinding htem that will release morphogens. Somites can influence, sonic headgehog will induce VGF, influence lateral plate mesodermal mesenchyme. Arteries or veins, by influenceing what signalling pathwya? - not just somites, the somites can also influences, formation of arterieis or veins, othe actual posution is very important. Location Location Location - gilbert statement. 13. What are the three distinct cell lineages involved in the formation of skeleton? Which germ layer(s) they originate from? What kind of skeleton they are making? *NICE 14. What are the two models of bone formation? What are the main differences between them (tissue origin and type of ossification)? Endochondral, Intramembroanous Ossifciation What are the (5) steps in endochondral ossification? NOT ON MIDTERM, BUT MAYBE ON FINAL 18. Where does intermediate mesoderm form? What organs will intermediate mesoderm develop into?, between paraxial and lateral plate mesoderm. Which signallying pathway invovled in segregation fo these 3 kinds of mesodberm? BMP, high conc at lateral plate mesoderm, low to nothing in the paraxial mesoderm. Lect 13/14 What are presumptive heart cells? What is cardiogenic mesoderm? - both sides of the primitve streak, 50 of them,, as they migrate, they are going throguh proliferation, through streak, end up in splanic mesoderm. Cardiogenic mesoderm at this point. Why are they migrateing as they do? What is the role of Wnts and BMPs in the specification of Heart precursor cells? - connect with endoderm. BMPs come from ventral to dorsal, WNTs from posterior to anterior, WINT hinhibitotrs are comign from anterior to posteriosr. Where there is overlap of B<PS and WNT inhibitiors, the signals necesary for the determination of the heart cells. Trasncirption fators. knwo. Similar situation: endoderm specification What is the role of endoderm in the migration of the cardiac precursor cells? Give one example - signals are comgin gfom the endoderm. Signals will guide cardiogenic mesodermal cells. Guide tube fusion of one heart, bec of proteins synthesizd from the endorderm/by the endoderm. Miles Apart. mutation -- the tubes wil nto buse if mutated. neurosn and schwann cells release signals to angiogeneisis Define and briefly explain organspecific angiogenesis?, reciprocla induciton? ** listen again What are hematopoetic inductive environments and what is their role in the differentiation of HSCs (Hompetiic stem cells) into different lineages? Cells make multiple transitions during development between epithelial and mesenchymal states. There are also many examples of communication between epithelial and mesenchymal structures. Think about example(s) for each of these two events, and about its role in development.

6 trasntion can be epthi and mesen to epith, but communication is didfferent, cells, signals, endoderm produceing signal, mesodermal heart cells to move etc.. do not mix. ** FINAL for sur e Lec 15 -roels of FGF 10 FGF 8 - WNTS 2b, 8c, 3 \ 3a -- apical -- differne,t nodnt need ot knwo. FGF10, FGF8 TBx5, tbx4, relationships between the factors. HOX GENES What is AER (give the full name)? What is PZ (give the full name)? How is the interaction between AER and PZ governing the limb growth?- qxes, 4th factor: time