Test Bank For Principles Of Development 6th Edition By Wolpert

Test Bank For Principles Of Development 6th Edition By Wolpert Feedback: No, the anterior-posterior positioning of the fore- and hindlimb is determined by the combinatorial action of Hox genes within the lateral plate mesoderm. Tbx transcription factors become expressed specifically in limb-forming regions, with Tbx5 in the prospective forelimb. Tbx factors control the local production of FGF-10, which in turn promotes the development of the apical ectodermal ridge (AER). The AER establishes a positive feedback loop that maintains consistent outgrowth of the limb from the side of the embryo. Page reference: 457 Type: multiple choice question Title: Chapter 10 - Question 03 03) Which of the following refers to a chemical or infection that interferes with embryonic development, leading to defects in the animal? *a. Teratogen Feedback: Yes, a teratogen is an external agent, such as a chemical or infection, that interferes with embryonic development, leading to defects in the embryo and the animal. Page reference: 472 b. Mutagen Feedback: No, a teratogen is an external agent, such as a chemical or infection, that interferes with embryonic development, leading to defects in the embryo and the animal. Some mutagens, those that cause mutations in a DNA sequence, can be teratogens but not all mutagens are teratogens. Page reference: 472 c. Morphogen Feedback: No, a teratogen is an external agent, such as a chemical or infection, that interferes with embryonic development, leading to defects in the embryo and the animal. Some morphogens, in large excess, can give rise to teratogenic effects. However, a teratogen is a strict term used for an external substance for its deleterious effects on the embryo. Page reference: 472 d. Carcinogen Feedback: No, a teratogen is an external agent, such as a chemical or infection, that interferes with embryonic development, leading to defects in the embryo and the animal. A carcinogen is an agent that causes cancer. Page reference: 472 Type: multiple choice question Title: Chapter 10 - Question 04 04) Which of the following intercellular signaling pathways directly controls the sequence of limb digits across the antero-posterior axis? a. FGF Feedback: No, Sonic hedgehog (Shh) is the polarizing morphogen within the developing limb. It is expressed within the posterior limb mesenchyme, within the zone of polarizing activity (ZPA). When the ZPA is transplanted to, or if Shh expression is forced in, the anterior limb mesenchyme, the limb develops mirror-image duplication of digits, bones, muscles, and tendons. Fibroblast growth factor controls the outgrowth of the limb from the side of the embryo. Page reference: 466 *b. Shh Feedback: Yes, Sonic hedgehog (Shh) is the polarizing morphogen within the developing limb. It is expressed within the posterior limb mesenchyme, within the zone of polarizing activity (ZPA). When the ZPA is transplanted to, or if Shh expression is forced in, the anterior limb mesenchyme, the limb develops mirror-image duplication of digits, bones, muscles, and tendons. Page reference: 466 c. Wnt Feedback: No, Sonic hedgehog (Shh) is the polarizing morphogen within the developing limb. It is expressed within the posterior limb mesenchyme, within the zone of polarizing activity (ZPA).