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TLS Online TPP Program

#Question id: 3974

 A leucine-zipper motif contains

#Unit 3. Fundamental Processes

  1. a stretch of five leucine residues in a row.

  2. a leucine residue at every seventh position.

  3. a leucine residue complexed with a zinc ion.

  4. an alternating leucine-alanine-proline structure.

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TLS Online TPP Program

#Question id: 1966

#Unit 4. Cell Communication and Cell Signaling

Mammals have Toll-like receptors (TLRs) that act in a manner similar to those of insects. While not specific to a particular pathogen, a TLR can recognize a kind of macromolecule that is absent from vertebrates but present in/on certain groups of pathogens. Which of the following is most likely to be recognized by a particular TLR that defends against some viruses?
TLS Online TPP Program

#Question id: 15653

#Unit 13. Methods in Biology

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. You have isolated a mutation that causes constitutive melibiase activity, which you designate MelA–. P1 phage mapping experiments using a Tn5 insertion linked to Mel1 show that MelA– is not linked to Mel1. Moreover you find that when an amber suppressor is introduced into a MelA– mutant, normal melibiase regulation is restored. Classify the MelA– mutation on the basis of genetic properties,  make a proposal for the type of regulatory functions affected by the MelA– mutation?
TLS Online TPP Program

#Question id: 33984

#Unit 2. Cellular Organization

Choose correct combination of statements 

A. Each chromosome contains many fragments of very long duplex of DNA, folded into a fiber that runs continuously throughout the chromosome.
B. During interphase, euchromatin, which is slightly densely packed than mitotic chromosomes. 
C. Regions of heterochromatin remain densely packed throughout interphase.
D. Various heterochromatic regions, especially those associated with centromeres, aggregate into a densely staining chromocenter
TLS Online TPP Program

#Question id: 31102

#Unit 2. Cellular Organization

Which of the following statements are correct regarding the actin polymerization?

a) the concentration of G-actin is above the Cc, the filament end will grow
b) the concentration of G-actin is below the Cc, the filament end will grow
c) (+) end of microfilament polymerization is much faster than the (-) end
d) D form that adds to the filament and the T form that leaves
TLS Online TPP Program

#Question id: 23096

#Unit 12. Applied Biology

which bioremediation approach involves using plants to degrade pollutants?