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?

TLS Online TPP Program

#Question id: 29452

#Unit 6. System Physiology – Plant

Auxins in biological samples can be determined by

a. bioassay

b. mass spectrometry

c. enzyme-linked immunosorbent assay 

d. The Avena coleoptile curvature assay

TLS Online TPP Program

#Question id: 29453

#Unit 6. System Physiology – Plant

Which of the following technique will be most effective for IAA concentrations of about 0.02 to 0.2 mg L–1

TLS Online TPP Program

#Question id: 29454

#Unit 6. System Physiology – Plant

Identify A, B and C in auxin synthesis

a. Tryptophan (Trp)----------A-------------→ Indole-3-pyruvic acid 

b. (IPA) -----------B------------→ Indole-3-acetaldehyde (IAld)

c. Indole-3-acetaldehyde (IAld) ------------C-----------→ I3AA

TLS Online TPP Program

#Question id: 29455

#Unit 6. System Physiology – Plant

which of the following auxin derivates compound that provide broad‐spectrum control of fungal pathogens

TLS Online TPP Program

#Question id: 29456

#Unit 6. System Physiology – Plant

In maize kernels, IAA also appears to be synthesized by a tryptophan independent pathway via

TLS Online TPP Program

#Question id: 29457

#Unit 6. System Physiology – Plant

Covalent conjugation of amino acids to IAA can also result in permanent inactivation (storage or degradation), here certain combination is given (∧ shows conjugation)

a. IAA ∧ myo-inositol/Gluc/Ala/Leu/Me ---Reversible (storage)

b. IAA ∧ myo-inositol/Gluc/Ala/Leu/Me ---irreversible (degradation)

c. IAA ∧ oxIAA/GH3-Asp-Glu/3-Methyleneoxidole ---Reversible (storage)

d. IAA ∧ oxIAA/ GH3-Asp-Glu/3-Methyleneoxidole---irreversible (degradation)

Which of the following is correctly paired