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2

There's no rule that says a transcription factor must be either a repressor or an activator. The lambda repressor (CI) is in fact a repressor and activator of transcription, depending on where it is bound and to what promoter you are referring to. I know your question isn't directly about lambda phage, but I think this mechanism may be best explained in the ...


2

I'm tempted to say, "It's complicated." CI does indeed act as both a repressor and activator. Transcription regulation in the lambda bacteriophage is quite complex for such a small system, so some confusion is understandable. Lewis et al. gives a rough description in a relatively recent paper (1): The CI protein autoregulates its synthesis. At low ...


3

Contrary to the question title, viral DNA can be methylated. See for example Bonvicini et al. 2012. (1) and Hoelzer et al. 2008 (2). Hoelzer et al. give a review of the presence and role of cytosine methylation in DNA viruses of animals: To understand the impact of cytosine methylation on the viral life cycle and the evolution of base composition, ...


1

First thing to make clear is that net $6$ $H_2O$ go out of the reaction.($12$$H_2O$ $-$ $6$$H_2O$) Let me tell you my calculation, you should then be able to figure out what went wrong. For the Left hand Side, $6$ $H_2O$ are accounted here : $2$ $H_2O$ go in conversion of 2-Phosphoglycertae to phosphoenolpyruvate. $2$ $H_2O$ in TCA from conversion of ...


1

I haven't found a manual for this machine, but my guess is that you exceed the maximum current which the power supply can provide. This is something I have experienced myself for electrophoresis. Usually power supplies then switch into the constant current mode at the maximum current they can deliver, which I think is what happens here. If the voltage you ...


2

It does make a difference on polyacrylamide. A and C are faster while G and T are slower. Image from publication: The "standards" are AAA/TTT/GGG/CCC molecules.


1

Practically speaking I have never seen a difference, but the agarose gels usually used in the lab do not have the highest resolution. There is one paper showing that the form (A- or B- form) and the GC-content play a role since DNA molecules of higher GC content are less flexible and therefore have more problems getting through the agarose matrix. ...


2

If it is a good idea to use PacBio depends a lot on what you want to sequence and what you want to do with the data you get. In short: you get longer reads but about 15% error per base. This means, you will have to cope with those errors, there are possibilities to do that. How much coverage you will get of you sample I cannot tell you, as I do not know what ...


6

You can run your DNA sample on agarose gel to see, whether you have significant degradation. If you are interested in contamination, you can make a standard photometric analysis to assess the 260/280 and 260/230 ratios and absorbance at 320 nm on NanoDrop or even something similar to Eppendorf's BioPhotometer. In case RNA may be an obstacle for some ...


1

Some bacteriophages adsorb on the pili. So the individuals carrying the F-element will be susceptible to these. F-plasmid encoded membrane protein PifA is responsible for the T7 resistance [See here]. The exact mechanism is not known If you see the list of references in the textbook chapter you will be able to trace the reference for a certain quoted fact ...


5

Yes, you can do this. As long as the final mix has the proper concentrations of everything, its fine. Just make sure you compensate the by adding 30 uL (the extra volume) less of water to the master mix.


4

The lipopolysaccharide layer of the Gram-negative bacterial cell wall is stabilised by divalent cations. Most recipes for disrupting E. coli cells include Tris-EDTA for this reason. I seem to just know this, so no reference at the moment. All nucleases require Mg2+, which is why there is EDTA in the stop buffer added to restriction digests. Carry-over of ...


3

A lot of enzymes need metal ion in their active center (it is actually the metal ion which is taking part in the catalyzed reaction). These are manganese, magnesium, copper and so on. For DNAses the metal in the active center is magnesium and EDTA simply chelates this ions, making them unavailable for the enzyme and thus hinders the enzyme from working. ...


1

The process is described here. This is my summary, plus a few extra details: The primary gene product of the INS gene is preproinsulin. As the N-terminal signal sequence (pre-) emerges from the ribosome during polypeptide elongation the signal sequence binds to a signal recognition particle which arrests elongation until the nascent chain has engaged with ...



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