With respect to the DNA methylation mechanism in mammalian cells, which of the following statements, if any, is true? 

I. The principal role of the DNMT1 DNA methyltransferase is in de novo methylation. 

II. The DNMT3A and DNMT3B DNA methyltransferases require hemi-methylated DNA as a substrate and are responsible for methylating nascent DNA strands that are complementary to methylated parental DNA strands.

III. Active DNA demethylation means removal of methyl groups from a hemi-methylated DNA double helix. 

IV. DNA methylation is not essential in mammalian development.

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#Question id: 13118

#Unit 2. Cellular Organization

GEF activity of monomeric G protein Ran perform in

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#Question id: 4431

#Unit 3. Fundamental Processes

Which of the following transcription factors enhance transcription without binding to DNA? 

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#Question id: 1898

#Unit 4. Cell Communication and Cell Signaling

Of the following, the single best defining description of a type IV hypersensitivity reaction is that it involves:

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#Question id: 24554

#Unit 9. Diversity of Life Forms

several species arise from a common ancestor over a short time called___

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#Question id: 7578

#General Aptitude

Joseph walked 1 km/hr slower than usual and he could return home in 9/8th of his usual time. His normal walking rate is