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Question
The stain that is used to view the bands of DNA molecules on agarose gel is
The stain that is used to view the bands of DNA molecules on agarose gel is
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Solution
The correct option is B ethidium bromide
Agarose gel is the solidified gel which serves as the matrix with definite pore size in gel electrophoresis. Gel electrophoresis is a laboratory technique that is based on separation of charged species (here DNA) in an electric field based on their sizes. The DNA molecules loaded in the well of agarose gel start migrating towards the positive terminal (anode) under the influence of the electric field. Under a specific voltage, the smaller DNA molecules can pass through the pores quite swiftly as compared to the larger DNA molecules. This creates different bands, each containing a DNA fragment of specific size.
The separated fragments in a mixture can be visualized by ethidium bromide staining followed by UV exposure. Ethidium bromide is added in the agarose gel once agarose powder is dissolved in buffer and mixed thoroughly. The stain gets dispersed throughout the gel. Ethidium bromide acts as an intercalating molecule. It gets inserted within the species present between the double helix of DNA. This absorbs wavelength corresponding to ultraviolet radiation and emits another wavelength that is visible to us.
Fig: (a) Ethidium bromide (EtBr) as an intercalating agent
(b) Gel containing DNA bands after ethidium bromide staining and UV exposure
On the other hand, bromophenol blue is a negatively charged molecule used as a tracking dye in gel electrophoresis. Similar to DNA, it also moves towards anode. Being visible in naked eyes, it helps to monitor how much the DNA has migrated.
Safranin is a basic stain generally used in cytology and histology experiments in the field of biology.
Methyl orange is a pH indicator that is generally used in acid-base titration reactions.
Agarose gel is the solidified gel which serves as the matrix with definite pore size in gel electrophoresis. Gel electrophoresis is a laboratory technique that is based on separation of charged species (here DNA) in an electric field based on their sizes. The DNA molecules loaded in the well of agarose gel start migrating towards the positive terminal (anode) under the influence of the electric field. Under a specific voltage, the smaller DNA molecules can pass through the pores quite swiftly as compared to the larger DNA molecules. This creates different bands, each containing a DNA fragment of specific size.
The separated fragments in a mixture can be visualized by ethidium bromide staining followed by UV exposure. Ethidium bromide is added in the agarose gel once agarose powder is dissolved in buffer and mixed thoroughly. The stain gets dispersed throughout the gel. Ethidium bromide acts as an intercalating molecule. It gets inserted within the species present between the double helix of DNA. This absorbs wavelength corresponding to ultraviolet radiation and emits another wavelength that is visible to us.
Fig: (a) Ethidium bromide (EtBr) as an intercalating agent (b) Gel containing DNA bands after ethidium bromide staining and UV exposure
On the other hand, bromophenol blue is a negatively charged molecule used as a tracking dye in gel electrophoresis. Similar to DNA, it also moves towards anode. Being visible in naked eyes, it helps to monitor how much the DNA has migrated.
Safranin is a basic stain generally used in cytology and histology experiments in the field of biology.
Methyl orange is a pH indicator that is generally used in acid-base titration reactions.
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