A mechanism for preventing sap loss entails closing sieve plate pores with callose, which is

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#Question id: 11808

#Unit 6. System Physiology – Plant

In addition to the free bases, which are the only active forms, active cytokinin levels are decreased through;

a) Addition of sugar molecule to the 3, 7, or 9 nitrogen of the purine ring, called glycosylation-mediated inactivation

b) cis-trans isomerisation of zeatin

c) Irreversible cleavage by cytokinin oxidases.

Which of the following is incorrect?

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#Question id: 1632

#Unit 4. Cell Communication and Cell Signaling

A single plasma cell secretes:

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#Question id: 5036

#Unit 5. Developmental Biology

 The experiments of Spemann and Mangold first defined what feature of amphibian embryos?

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#Question id: 16127

#Unit 13. Methods in Biology

You are studying regulation of the yeast enzyme glutamine synthetase (GS), which is encoded by the GLN1 gene. You have isolated two mutants, designated  gln2– and gln3–, that give decreased GS activity. Mating of either gln2– or gln3– haploids to wild type produces heterozygous diploids that show normal amounts of GS expression. When you cross either a gln2– or gln3– haploid to a gln1– strain the resulting diploids show normal expression of GS.

The GLN1 gene shows a rather complex regulation in response to different amino acids. When either glutamate (glu) or glutamine (gln) is added to the medium, the amount of GS expression diminished and when both glutamate and glutamine are added to the medium GS expression is shut off completely. The effects of different mutants on the response to glu and gln are shown below.

Which of the models from best fits these experimental results? Complete the model for the regulation of GLN1 that includes the effects of glu and gln.      

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#Question id: 28351

#Unit 5. Developmental Biology

Oskar mRNA becomes complexed with plus-directed motor protein in the oocyte, it moves to the growing end of the microtubules at the posterior region, where the translation occur but inhibition of Oskar translation is mediated by____