You are studying a new strain of E. coli that can utilize the disaccharide melibiose very efficiently. You find that utilization depends on the enzyme melibiase, which is encoded by the gene Mel1. Mel1 is not expressed unless melibiose is present in the growth medium.

Next, you isolate a third mutant, MelC–, which gives constitutive melibiase expression. The MelC– mutation is closely linked to Mel1 and MelB–. Genetic tests of the MelC– mutation yield the following:

 

As above, classify the MelC– mutation in terms of its basic genetic properties and explain how you arrived at your conclusions.

#Question id: 11843

#Unit 6. System Physiology – Plant

During an experiment Six-day-old pea seedlings were grown in the dark in the presence of 10 ppm (parts per million).  Firstly, Grown seedling treated with ethylene and secondly grown seedling left untreated. What will be the conclusion has been drawn from this experiments?      

#Question id: 11844

#Unit 6. System Physiology – Plant

The following statements are made to describe the biosynthetic pathway of IAA;

a)  IPA pathway involves a deamination reaction to form IPA, followed by a decarboxylation reaction to form indole-3-acetaldehyde (IAld) and then oxidized to IAA by a specific dehydrogenase

b) IAN pathway is similar to the IPA pathway, except that the order of the deamination and decarboxylation reactions is reversed, and different enzymes are involved

c) IAM pathway  involves the two enzymes  tryptophan monooxygenase and IAM hydrolase

d) In the IAN pathway, tryptophan is first converted to indole-3-acetaldoxime and then to indole-3-acetonitrile. The enzyme that converts IAN to IAA is called nitrilase

Which of the following is the correct  statements  of about the biosynthesis of  IAA?

#Question id: 11845

#Unit 6. System Physiology – Plant

IAA Is synthesized from__

#Question id: 11846

#Unit 6. System Physiology – Plant

In maize  orange pericarp (orp) mutant is

#Question id: 11847

#Unit 6. System Physiology – Plant

On the basis of isotopic labeling and metabolite identification, oxidative pathways are more likely to be involved in the controlled degradation of IAA by____

Statement-I ___IAA is oxidized without decarboxylation to OxIAA

Statement-II___ IAA-aspartate conjugate is oxidized first to the intermediate dioxindole-3-acetylaspartate, and then to OxIAA

#Question id: 11848

#Unit 6. System Physiology – Plant

Polar transport is specific for active auxins, such as