E55-2009 practice exam 3

B the heart forms from a sheet of cells that

Info icon This preview shows pages 4–7. Sign up to view the full content.

View Full Document Right Arrow Icon
B. The heart forms from a sheet of cells that invaginates to make a tube. C. The blood forms exclusively from sheets of cells in the anterior lateral plate. D. The vessels form exclusively from sheets of cells in the anterior lateral plate. E. none of the above ______19. A mouse knockout for Fgf10 would be expected to result in: A. conversion of all appendages to a hindlimb identity B. halt of limb bud outgrowth C. failure of limb bud formation D. absence of posterior digit identities in the limb E. absence of anterior digit identities in the limb ______20. Stem cells are characterized by: A. the ability to produce numerous differentiated cell types B. the ability to self-renew (produce more of themselves) C. they are visibly undifferentiated D. they have been located in adult organs E. all of the above
Image of page 4

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
E-55, Exam 3-2009: Name Page 5 of 9 Short answer (point values indicated) . Provide a concise response in the space provided. 21. (12 points) Limb growth and patterning are closely intertwined, and the AER is a key signaling center in this series of events. Several stages of forelimb extension are shown below (labeled 1-4). Forming bony elements are depicted in gray, with their anatomical names labeled in the complete limb (stage 4). A. Label the AER in stage 1. Then, in the space below define the AER : what cells comprise it, and how would these cells appear if you looked at a three-dimensional limb bud during stages 1-3 shown above? B. Based on the known role of the AER, list what bony elements will form if the AER is removed at the following stages: Stage 1: _________________________________________ Stage 2: _________________________________________ Stage 3: _________________________________________ C. Describe an experiment that would rescue the effect of removing a Stage 1 AER, but would not require a graft of cells with ‘AER activity.’ D. You remove the AER of a stage 3 limb, and then graft the AER of a stage 1 limb in its place. What will happen? In your answer, clearly state which bony elements of the limb will form. What does this result tell us about the information provided by the AER ?
Image of page 5
E-55, Exam 3-2009: Name Page 6 of 9 22. (6 points) Before discovery of the true signal that operates in limb development anterior-posterior patterning, retinoic acid was a leading candidate. Retinoic acid is a small molecule compound derived from Vitamin A. When retinoic acid is soaked onto a charged plastic bead and implanted into the anterior region of a young limb bud, the fully developed limb formed mirror image duplications of the digits. A. Based on this result, retinoic acid is a candidate for the activity of which signaling center in the limb? B. Name 3 additional criteria that retinoic acid would need to meet in order to be the signal from the aforementioned signaling center? 1 . ____________________________________________________ 2.____________________________________________________ 3 . ____________________________________________________ 23. (4 points) X-chromosome inactivation is a key regulatory event during mammalian development. Circle the correct responses: (A) X-inactivation in the early blastocyst (i.e. before ICM stage) occurs: randomly OR on the maternal X chromosome OR on the paternal X chromosome (B) X-inactivation after the ICM forms and during subsequent development occurs: randomly OR on the maternal X chromosome OR
Image of page 6

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern