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DNA fragments are negatively charged molecules. They are separated by forcing them to move towards positive electrode under an electric field through a medium/matrix.

1. DNA fragments are negatively charged molecules. They are separated by forcing them to move towards positive electrode under an electric field through a medium/matrix.
2. Increasing the concentration of agarose in the gel reduces the migration rate of DNA fragments. DNA fragment can not be visualised directly but can be visualised under UV light after staining with ethidium bromide.
3. Restriction enzymes belong to a larger class of enzymes called nucleases. Nucleases are of two different kinds: exonucleases (which remove nucleotides from the end of a DNA molecule) and endonucleases (which break internal phosphodiester bonds at palindromic sites that are highly specific).
4. DNA Polymerase I possesses a 3’→5’ exonuclease activity or "proofreading" function, which lowers the error rate during DNA replication, and also contains a 5’→3’ exonuclease activity, which enables the enzyme to replace nucleotides in the growing strand of DNA by nick translation.

Correct answer: DNA fragments are negatively charged molecules. They are separated by forcing them to move towards positive electrode under an electric field through a medium/matrix.

Solution

DNA has a negatively charged phosphate backbone, so in an electric field it migrates toward the positive electrode. A porous medium like agarose slows larger fragments more than smaller ones, allowing separation.

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• The separated DNA fragments can be visualised only after staining the DNA with Ethidium bromide followed by exposure to UV radiation.

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