Question

What is agarose gel? How is it used in DNA ?

Answer 1

Hint: DNA is hereditary material for humans and almost all other species. Almost every cell in the body of a human has the same DNA. Human DNA has about 3 billion bases, and according to the U.S., National Library of Medicine(NLM) more than 99 percent of these bases are the same for all people.

Complete answer:
Agarose is a high-molecular-weight polysaccharide derived from the cell walls of some marine red algae. Agarose does not dissolve in cold water but dissolves quickly in boiling water. On cooling, agarose chains form side-by-side aggregates that condense into a three-dimensional, interlocking network of non-covalent hydrogen bonds. Since each individual gel fibre contains several agarose chains, agarose gels are relatively solid.

Agarose gel electrophoresis is widely performed in life science laboratory techniques. Researchers apply this procedure to separate biological molecules depending upon their size. DNA has an unique chemical structure where the nucleobases, the letters of the DNA code, are accompanied by a backbone of sugar, deoxyribose, and the phosphate group.The backbone of DNA consists a negative charge for each nucleobase present, keeping the mass-to-charge ratio of DNA identical across various fragment sizes. Because of this negative charge, when we add an electrical field to a DNA-containing solution, the DNA molecules can pass to a positively charged electrode.

In agarose gel electrophoresis, we add a gel matrix, a few layers of sieves or nets that the DNA migrates along the voltage gradient to the positive electrode.This matrix induces resistance and that smaller molecules migrate faster while larger molecules migrate very slowly. The variation in migration rate is really how we separate the different sizes of the DNA molecule in order to decide their length. The gel matrix is formed by dissolving a natural polysaccharide called agarose, obtained from a type of algae, usually containing about 1% agarose and allowing it to form a gel. The pore size of this gel matrix is well suited for DNA separation and the rate of migration can be influenced by increasing or decreasing the percentage of agarose in the mixture.

Note: Agarose can be modified to produce low melting agarose by hydroxyethylation. Low melting agarose is commonly used when the isolation of separated DNA fragments is required. Hydroxyethylation decreases the packing density of the agarose bundles and reduces their pore size effectively.