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: 15961

#Unit 12. Applied Biology

In somatic hybridization experiments, only the heterokaryotic or 'hybrid' protoplasts, form only a small proportion of the population. Therefore, an effective strategy has to be employed for their identification and isolation, this step is called;

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#Question id: 32389

#Unit 2. Cellular Organization

Vertebrate skeletal muscle contraction, also depends on set of specialized accessory proteins that is troponin, which is closely associated with the actin thin filaments. Troponin is a complex of three polypeptides except;

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#Question id: 2124

#Unit 2. Cellular Organization

An integral membrane protein can be extracted with:

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#Question id: 31069

#Unit 2. Cellular Organization

Human SCF complexes contains a phosphoserine/threonine-binding protein, known as:

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#Question id: 31309

#Unit 1. Molecules and their Interaction Relevant to Biology

Which one of the following interactions pairs plays least role in stabilizing B-DNA?