Ribosomes have relatively small molecular weights in comparison to cell organelles, and relatively large molecular weights in comparison to macromolecules (such as proteins). Several rounds of centrifugation, using slightly different conditions, is a feasible way to isolate intact ribosomes.

SDS-PAGE is an excellent technique for separating denatured proteins based on molecular weight. Western blotting is used to detect the presence specific proteins in a sample. Dialysis is often used in protein purification procedures.

The only answer that will viably pull a protein complex out of a solution is co-immunoprecipitation. Co-immunoprecipitation involves using a large amount of antibody for a specific protein to capture the protein of interest and anything that is associated with it (namely the protein complex). The proteins can then be eluted from the antibody and analyzed.

FRET involves fluorescently labeling two proteins to look for, amongst other possible uses, protein-protein interactions in vivo. Southern blotting is a technique used to separate and identify a specific DNA sequence in a solution. Mass spectrometry can be used to analyze and sequence proteins, but does not directly involve the use of antibodies.

Ethidium bromide intercalates into the hydrophobic interior of the DNA double helix and remains bound through Van der Waals interactions. The binding of ethidium bromide to DNA leads to a conformational shift that increases its fluorescence.

Obtaining two distinct contigs from a sequencing reaction suggests that either this virus has two separate chromosomes, or that there is some type of error in the sequencing reaction. 

The most direct way to test this would be to run a Northern blot analysis with probes against the two potential chromosomes. If they are unique chromosomes, we would expect to see a band that matches the length of the sequenced product on the gel per chromosome. If it is an error, both probes should yield a band of the same size, suggesting that there is only one chromosome.

A Southern blot tests for the presence of DNA; therefore, that would not be useful. A protein gel would also not be useful in this case since we are trying to determine the presence of RNA. A PCR will also not be fruitful since it cannot be conducted on RNA.

Note that a reverse-transcription PCR could potentially be useful because it would convert the RNA into DNA; in that case, you can design mulitple combinations of primers if you think it is a single chromosome.

These are all important steps to create a usable DNA extraction. First, the tissues are homogenized, generally chemically or mechanically. The proteins are then removed from the sample by denaturation. Any contaminants can be removed by multiple methods with organic solvents. Depending on the situation, some other steps are involved, such as removal of RNA from the extract. Lastly, the DNA is precipitated via an alcohol into a pure DNA extract.

The correct answer is SDS. SDS disrupts non-covalent bonds in proteins ultimately denaturing these proteins. Both ammonium persulfate and TEMED are reagents used to polymerize (or solidify) SDS-page gels for western blot applications. EDTA chelates cations in solution preventing the activity of proteases that may degrade the primary amino acid structure. Acrylamide is the substance that is polymerized in the SDS-gel, giving the viscous physical characteristics to the gel. 

Flow cytometry utilizes antibodies specific to a protein expressed by a single cell type. Antibodies can be coated onto magnetic beads, and those antibodies will bind only cells with the proper proteins, thus becoming "stuck" to the beads which can be separated out from the sample. Centrifugation will not be able to detect such small differences, and is only useful if the density is different. Co-IP is more appropriate when looking for proteins that interact or colocalize. Southern blotting is for DNA detection, and X-ray crystallography is for understanding protein structure.