Do all strands of the same length have the same sequence of base pairs? I wouldn't think so, and this would be a problem in the next step, determining the sequence of one size fragment by using special base pairs that are lacking a hydroxyl group.
https://biology.stackexchange.com/questions/8024/separating-dna-fragments-by-gel-electrophoresis-are-all-the-strands-for-one-siz
Because DNA and RNA are negatively charged molecules, they will be pulled toward the positively charged end of the gel. Proteins, however, are not negatively charged; thus, when researchers want to separate proteins using gel electrophoresis, they must first mix the proteins with a detergent called sodium dodecyl sulfate.
http://www.nature.com/scitable/definition/gel-electrophoresis-286
Typically, a DNA molecule is digested with restriction enzymes, and the agarose gel electrophoresis is used as a diagnostic tool to visualize the fragments. An electric current is used to move the DNA molecules across an agarose gel, which is a polysaccharide matrix that functions as a sort of sieve.
https://askabiologist.asu.edu/agarose-gel-electrophoresis
You are correct: strands of the same length do not necessarily have the same sequence. The separation of DNA in gel electrophoresis is purely based on the hydrodynamic size. The number of fragments produced by restriction enzyme digestion depends on the number of sites for that particular enzyme in your input DNA.
https://biology.stackexchange.com/questions/8024/separating-dna-fragments-by-gel-electrophoresis-are-all-the-strands-for-one-siz
The smaller molecules are able to navigate the mesh faster than the larger one, so they make it further down the gel than the larger molecules. This is how agarose electrophoresis separates different DNA molecules according to their size. The gel is stained with ethidium bromide so you can visualize how these DNA molecules resolved into bands along the gel. Southern blotting may also be used as a visualization technique for agarose gels.
https://askabiologist.asu.edu/agarose-gel-electrophoresis
Proteins vary greatly in mass but not in density. The average density of a protein is 1.37 g/cm3. Unless a protein has an attached lipid or carbohydrate, its density will not vary by more than 15 percent from this value. Table 3-1 lists the density and other physical characteristics of several blood proteins.
https://www.ncbi.nlm.nih.gov/books/NBK21589/
Two-dimensional gel electrophoresis, a technique for separating proteins based on their charge and their mass. (a) Preparation of a two-dimensional protein gel by isoelectric focusing (IEF) followed by SDS electrophoresis. (b) Two-dimensional gel of protein (more...)
https://www.ncbi.nlm.nih.gov/books/NBK21589/
Centrifugation is used for two basic purposes: (1) as a preparative technique to separate one type of material from others and (2) as an analytical technique to measure physical properties (e.g., molecular weight, density, shape, and equilibrium binding constants) of macromolecules.
https://www.ncbi.nlm.nih.gov/books/NBK21589/
gel electrophoresis. Gel electrophoresis is a laboratory method used to separate mixtures of DNA, RNA, or proteins according to molecular size. In gel electrophoresis, the molecules to be separated are pushed by an electrical field through a gel that contains small pores.
http://www.nature.com/scitable/definition/gel-electrophoresis-286
The text says that once the different size strands are separated by electrophoresis, you can just cut out one of the bands and work with that. That makes sense if you are guaranteed to only have 1 strand at that level of the gel agar or if the multiple strands are all the same exact sequence.
https://biology.stackexchange.com/questions/8024/separating-dna-fragments-by-gel-electrophoresis-are-all-the-strands-for-one-siz
which technique allows one to separate dna molecules by size?
Gel electrophoresis is a technique that allows one to separate DNA molecules by size. Gel electrophoresis technique allows one to separate DNA molecules by size.