The common ancestors of birds and mammals were very early (stem) reptiles, which almost certainly possessed 3-chambered hearts (2 atria, 1 ventricle). Birds and mammals, however, are alike in having 4-chambered hearts (2 atria, 2 ventricles). The 4-chambered hearts of birds and mammals are best described as

#Question id: 23315

#General Aptitude

#Question id: 4321

#Unit 3. Fundamental Processes

A genetic test to detect predisposition to cancer would likely examine the APC gene for involvement in which type(s) of cancer?

#Question id: 7274

#Unit 5. Developmental Biology

The following experiment is designed to study the role of several hormones in the regulation of metamorphosis in frogs.

 If the thyroid gland were removed from the tadpoles in Group 3, metamorphosis would

#Question id: 18370

#Unit 12. Applied Biology

#Question id: 10342

#Unit 6. System Physiology – Plant

Nitrate reductase is an important enzyme for nitrate assimilation. Given below some regulation of nitrate reductase activity through phosphorylation and dephosphorylation.

a) Light, and other environmental factors stimulate a protein phosphatase that dephosphorylates a key serine residue in the hinge 1 region of nitrate reductase and thereby activates the enzyme

b) In Dark, and Mg2+ stimulate a protein kinase that phosphorylates the same serine residues, which then interact with a 14-3-3 inhibitor protein, and thereby inactivate nitrate reductase

c) In Light, and Mg2+ stimulate a protein kinase that phosphorylates the serine residues, and thereby activate nitrate reductase

d) In Dark, and other environmental factors stimulate a protein phosphatase that dephosphorylates a key serine residue in the hinge 1 region of nitrate reductase and thereby inactivates the enzyme

Which of the following statements about regulation of nitrate reductase is correct?