G1/S phase CDKs and S phase CDKs, prevents reloading of MCM helicases by____

#Question id: 7246

#Unit 5. Developmental Biology

Treatment of Xenopus embryos with lithium dorsalizes the embryos by interfering with cell-cell signaling pathways. What, if anything, is the effect of lithium on hydra, and what might we infer about its mechanism of action?

#Question id: 7247

#Unit 5. Developmental Biology

Which statement correctly characterizes regeneration in the mammalian nervous system?

#Question id: 7248

#Unit 5. Developmental Biology

Planning of the Xenopus mesoderm along the dorso-ventral axis contains an antagonistic relationship between chordin and bmp-4. Is there an analogy here to dorso-ventral patterning in the Drosophila embryo?

#Question id: 7249

#Unit 5. Developmental Biology

Match the following proteins (column I) in nematodes with their functions (column II).

Which of the following is correct?

#Question id: 7250

#Unit 5. Developmental Biology

Following statements are regarding to signals that regulate axis extension in chick embryos.

A. In the stage 10 chick embryo, Fgf8 inhibits expression of the retinoic acid (RA) synthesizing enzyme Raldh2 in the presomitic mesoderm and the expression of the RA receptor RARβ in the neural ectoderm, thus preventing RA from triggering differentiation in the caudal-lateral epiblast cells and the caudal-most paraxial mesoderm.

B. Fgf8 inhibits Sonic hedgehog (Shh) expression in the neural tube floorplate, controlling the onset of ventral patterning genes.

C. FGF signaling is also required for expression of Delta1 in the medial portion of the caudal-lateral epiblast cells and promotes expression of Wnt8c.

D. Fgf8 decays in the caudal paraxial mesoderm, Wnt signaling, most likely provided by Wnt8c, now acts to promote Raldh2 in the adjacent paraxial mesoderm. RA produced by Raldh2 activity expresses Fgf8 and Wnt8c.

Which of the following statements are correct?

#Question id: 7251

#Unit 5. Developmental Biology

Following statements are regarding to the three “toggle switches” activated along the anterior-posterior axis to establish gap gene domains in drosophila.

A. The mutual inhibition of Knirps and Hunchback positions the Knirps protein domain at around 60–80% along the anterior-posterior axis.

B. Hunchback inhibits Krüppel expression at high concentrations but promotes it at intermediate concentrations.

C. Hunchback inhibits Krüppel expression at intermediate concentrations but promotes it at high concentrations.

D. Krüppel and Giant mutually inhibit each other’s synthesis.

E. Kruppel inhibits Giant expression at high concentrations but promotes it at intermediate concentrations.

Which of the following statements are correct?