Which of the following statements is true about formation of the primitive streak ?

A. by the cellular dance mechanism, the cells came down the sides of the epiblast to undergo a medially directed intercalation of cells in the posterior margin where primitive streak forms.

B. Cellular dance is mediated by wnt planar cell polarity pathway in the hypoblast cells, at the posterior edge of the embryo.

C. The Wnt pathway activated by fibroblast growth factors (FGFs) produced by the hypoblast.

D. The Wnt planar cell polarity pathway activated by b-catenin produced by the epiblast.

#Question id: 1395

#Unit 4. Cell Communication and Cell Signaling

Which of the following mutations would promote malignancy in cells whose proliferation is inhibited by TGFβ?

a. overexpression of Smad2               

b. loss of Smad 4

c. overexpression of TGFβ receptor I

d. loss of TGFβ receptor II

#Question id: 1396

#Unit 4. Cell Communication and Cell Signaling

Trks are:

a. endonucleases.        b. transmembrane receptors.   c. proteases.     d. protein kinases.      

#Question id: 1397

#Unit 4. Cell Communication and Cell Signaling

The vertebrate equivalent of CED-9 is:

#Question id: 1398

#Unit 4. Cell Communication and Cell Signaling

Which of the following properties is (are) characteristic of a benign tumor?

a. well differentiated              b. localized to tissue of origin             c. metastatic               

d. promotes angiogenesis        e. surrounded by a fibrous capsule

#Question id: 1399

#Unit 4. Cell Communication and Cell Signaling

Loss-of-function mutations in which of the following genes typifies colorectal carcinomas?

a. myc              b. K-ras                       c. p53              d. APC

#Question id: 1400

#Unit 4. Cell Communication and Cell Signaling

Which property is shared by malignant tumor cells and transformed cells in culture?

a. reduced growth factor requirement                        b. attachment-dependent growth

c. loss of actin microfilaments                                    d. altered morphology