TLS Online TPP Program

#Question id: 4703


Within a few weeks of treatment with the drug 3TC, a patientʹs HIV population consists entirely of 3TC-resistant viruses. How can this result best be explained?

#Unit 11. Evolution and Behavior
  1. HIV can change its surface proteins and resist vaccines.

  2. The patient must have become reinfected with 3TC-resistant viruses.

  3. HIV began making drug-resistant versions of reverse transcriptase in response to the drug.

  4. A few drug-resistant viruses were present at the start of treatment, and natural selection increased their frequency.

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TLS Online TPP Program

#Question id: 11732

#Unit 6. System Physiology – Plant

Cytokinins are defined as compounds that have biological activities similar to those of trans-zeatin. These activities include the ability to do the following:

a) Induce cell division in callus cells in the presence of an auxin

b) Promote bud or root formation from callus cultures when in the appropriate molar ratios to auxin

c) promote senescence of leaves

d) Promote expansion of dicot cotyledons

Which one of the following activities are incorrect?

TLS Online TPP Program

#Question id: 11733

#Unit 6. System Physiology – Plant

The synthetic cytokinin compounds that have not been identified in plants, these are;

TLS Online TPP Program

#Question id: 11734

#Unit 6. System Physiology – Plant

Some molecules act as cytokinin antagonists, which are able to block the action of cytokinins that is

TLS Online TPP Program

#Question id: 11735

#Unit 6. System Physiology – Plant

In cytokinin biosynthesis is the addition of the isopentenyl side chain from DMAPP to an adenosine moiety. The plant and bacterial IPT enzymes differ substrate used;

a) the bacterial enzyme utilizes AMP

b) the plant enzyme appears to utilize AMP

c) the bacterial enzyme utilizes both ADP and ATP

d) the plant enzyme appears to utilize both ADP and ATP

TLS Online TPP Program

#Question id: 11736

#Unit 6. System Physiology – Plant

Many plant tissues contain the enzyme cytokinin oxidase, which cleaves the side chain, except

TLS Online TPP Program

#Question id: 11737

#Unit 6. System Physiology – Plant

Cytokinins have been shown to have effects on many physiological and developmental processes, including____

a) Leaf senescence

b) Apical dominance

c) Gametophytic  development

d) Vascular development

e) Breaking of bud dormancy

f) Causing bud dormancy