#Question id: 7108
#Unit 5. Developmental Biology
Relative to the primitive streak and Henson's node, somite formation in the chick embryo occurs:
#Question id: 7218
#Unit 5. Developmental Biology
Following statements are regarding to convergent extension of the dorsal mesoderm in xenopus.
A. For convergent extension the first force is a polarized cell cohesion wherein the involuted mesodermal cells intercalate and the second force is differential cell cohesion.
B. The intercalations of mesodermal cells, both mediolaterally and radially, are stabilized by the planar cell polarity (PCP) pathway that is initiated by Wnts independent of β-catenin signaling.
C. The intercalations of mesodermal cells, are stabilized by the planar cell polarity (PCP) pathway that is initiated by Wnts dependent of β-catenin signaling.
D. Another factor regulating convergent extension is calcium influx from environment.
E. Ca2+ is released from intracellular stores and is required for convergent extension.
Which of the following combination is correct?
#Question id: 28358
#Unit 5. Developmental Biology
Which of the following protein is responsible for the localization of nanos mRNA at the posterior end and also involved in germ cell determination?
#Question id: 10325
#Unit 9. Diversity of Life Forms
Ultimately, which of these serves as the basis for both the principle of maximum parsimony and the principle that shared complexity indicates homology rather than analogy?
#Question id: 4957
#Unit 11. Evolution and Behavior
How many half-lives should have elapsed if 6.25% of the parent isotope remains in a fossil at the time of analysis?