Key Midterm Exam 2

MCDB 112 Midterm 1 | 100 points | Name__________________________________ SEAT #_____ 4. (6 Points) Briefly describe one of the two models of nodal flow. Nodal flow model: Ciliary vortical motion at the gastrulation node (or equivalent structure) directs extracellular movement of determinants (NVPs) Fling morphogens across the midline Two cilia model: Non-motile cilia act as mechanosensors of flow and transduce signal via unidirectional Ca+ release 3 Points Describe (in one to two sentences) an experiment that provided evidence in support of one of the models. For model 1 Mouse mutants lacking cilia or human mutants with L/R patterning defects (not really an experiment but I would accept it) Or the artificial flow experiment wherein persistaltic pumps created a simulation of cilia and found it was able to reverse the flow Reversed the flow and found the opposite patterning of nodal For Model 2 Observed asymmetric Ca2+ fluxes/flashes/transients 2 points Did the result provide correlative evidence, necessity, and/or sufficiency? Mouse mutants (with absent or altered missing cilia lacked nodal flow and) had L/R patterning defects (necessity) Or the artificial flow experiment wherein persistaltic pumps created a simulation of cilia and found it was able to reverse the flow (sufficiency) Reversed the flow and found the opposite patterning of nodal (same as above, sufficiency) Asymmetric Ca2+ flashes (correlative) 1 point 5. (12 Points) Bianchi et al. investigated the role of Juno as the Izumo receptor in fertilization. Fill in the key conclusions, briefly describe the experiment performed, and identify the experimental finding that supports the conclusion. a) Juno is necessary for sperm/egg binding/fusion? (1 pt) and thus for fusion/fertilization (1 pt) 3

MCDB 112 Midterm 1 | 100 points | Name__________________________________ SEAT #_____ 9. (6 Points) Which of the following statements are true / false about the primitive streak? Correct any false statements. a. Similar to the chick embryo, the early human embryo also depends on cell migration through a primitive streak True b. Cell migration through the primitive streak enables the formation of the three germ layers. ___ True OR False- endoderm and mesoderm (cells that give rise to ectoderm do not travel through streak) ___________________________________________________________________ c. There is no primitive streak in frog embryos. True d. Hypoblast cells are replaced by cells that migrate through the primitive streak to form embryonic endoderm. True e. The primitive streak forms at the posterior end of the chick embryo. _________ False _________________________________ 10. (7 points) You are a goat herder and you have one goat that produces 10X more of the finest goat milk than any other goat you have heard of. Her name is Milka. You want to clone her! Fill in the blanks of the steps you need to take. Harvest __oocytes/eggs___________ , remove _ _nucleus_or mitotic spindles_ _______, collect ______ _somatic /adult cells_ _______from Milka, fuse with ________ oocytes/eggs_ ___, grow to _________ __blastocyst__ ___ stage in culture, transfer to _____ womb/uterus __________ of a ________ surrogate/related mother _________. 1 point for each 11. (6 points) Indicate which of the following developmental processes depend on Wnts, BMPs, both or neither: _______ both ________Neural crest specification ___ both (or Wnt) ____A/P patterning in frogs _______ both ________A/P patterning in chick _______ both ________A/P patterning in mammals _______ BMP ________L/R patterning in birds and mammals ____ both (or BMP) ____ D/V patterning in frogs (both is technically best answer but bmp was emphasized in class 1 point for each (½ point if they say both and it was only one or the other, ½ point if they say one or the other and it was both) 6