Releasers may be ____________.

#Question id: 7185

#Unit 5. Developmental Biology

Following statements are regarding to establishing the three separate cell lineages in the mouse blastocyst.

A. The first two cell types to be specified are the inner cell mass and the trophectoderm. This involves progressive restriction of expression of the genes that code for transcription factors Oct4 and Cdx2.

B. At the eight-cell stage, all the cells express both genes at low levels, but by the late morula/early blastocyst stage, Cdx2 expression has increased in, and eventually becomes restricted to, the cells on the outside of the embryo, and these will form trophectoderm. Oct4

expression becomes restricted to the inner cell mass cells at early blastula stage.

C. Within the inner cell mass, two separate cell types arise: the epiblast cells, from which the embryo will develop; and the primitive endoderm, which will form extra-embryonic structures. This involves a progressive restriction of expression of the genes for the transcription factors Nanog and Gata6.

D. At the early blastula stage, some of the inner cell mass cells apparently at random start to express higher levels of Nanog, whereas the other cells express higher levels of Gata6.

E. By the late blastula, the cells expressing the two different transcription factors have sorted out within the inner cell mass so that cells expressing high levels of Nanog form an outer epithelial layer of primitive endoderm enclosing the epiblast cells expressing high levels of Gata6.

Which of the following statements are correct?

#Question id: 7186

#Unit 5. Developmental Biology

In dictyostelium stalk and spore cell maturation depends on cAMP level. Which of the following statement is incorrect regarding to this process?

#Question id: 7187

#Unit 5. Developmental Biology

Following statements regarding to feedback loops during limb development.

A. When the limb bud is relatively small, an initial positive feedback loop is established between Fgf10 produced in the mesoderm and Fgf8 produced in the ectoderm, promoting limb outgrowth.

B. As the limb bud grows, the ZPA is established, and another regulatory loop is created by inhibiting the BMP in mesoderm and maintain FGF expression.

C. In anterior region of the limb bud, Fgf8 positively regulates Etv4/5, which in turn repress Shh in this region, further reinforcing the posterior-to-anterior gradient of Shh from the ZPA.

D. In posterior region of the limb bud, Fgf8 positively regulates Etv4/5, which in turn repress Shh in this region, further reinforcing the posterior-to-anterior gradient of Shh from the ZPA.

Which of the following combinations are incorrect?

#Question id: 7188

#Unit 5. Developmental Biology

when RNAi completely eliminates beta-catenin from non-regenerating flatworms then which of the following results are obtained?

#Question id: 7189

#Unit 5. Developmental Biology

Following statements were made regarding vulval development in C. elegans:

A. The formation of the anchor cell is mediated by lin-12, the C. elegans homologue of the Notch gene.

B. The formation of the anchor cell is mediated by lin-12, the C. elegans homologue of the Delta gene.

C. The lin-12 gene needs to function only in that cell destined to become the uterine precursor cell.

D. Presumptive Anchor cell also need lin-12.

E. Two cells originally synthesize both the signal for uterine differentiation (the LAG-2 protein, homologous to Delta) and the receptor for this molecule (the LIN-12 protein, homologous to Notch.

Which one of the following options represents a combination of correct statements?

#Question id: 7190

#Unit 5. Developmental Biology

In amphibia, few mutants (Column A) and their affected event or organ (Column B).

Which of the following is correct?