Question

DNA fragments separated by gel electrophoresis are shown. Mark the correct statement-

A. Band 3 contains more positively charged DNA molecules than 1
B. Band 3 indicates more charge density than 1 and 2
C. Band 1 has longer DNA fragments than 2 and 3
D. All the bands have equal lengths and charges but differ in base composition

Answer 1

Hint:
A technique for separating and analysing several kinds of macromolecules, including DNA, RNA, and proteins, is gel electrophoresis. Using this technique, protein and nucleic acid fragments are divided according to size and charge. On the basis of size and charge, it is used to separate a combination of DNA and RNA fragments.

Complete step by step answer:
The technique of gel electrophoresis enables the selection of desired macromolecules from a variety of nucleic molecule mixtures. The size and charge of molecules are used in this technique to separate them. After DNA has been amplified using the PCR technique, it is a valuable technique to segregate DNA for analytical purposes. In this method, the gel is used as the medium, and an electric field is used to force molecules through it. Typically, agarose or polyacrylamide is used as the gel. The molecule is propelled through the gel by the electric field's negative charge end. The molecule is drawn through the gel by the positive charge at the other end of the electric field. The media containing the molecules that need to be separated are introduced into the gel's well. The gel is now put into an electrophoresis chamber, which is powered by a source of electricity. Larger molecules move slowly through the gel as a result of the power source's electric field, while smaller molecules move more quickly.
Agarose, the gel in use, creates a matrix that is both solid and porous. Long, unbranched strands of uncharged, cross-linked carbohydrates make up agarose. This produces a gel with sizable pores that is appropriate for separating macromolecules. When DNA-containing media are subjected to agarose gel electrophoresis, DNA molecules move toward the positive end of the gel. Because DNA has a negative charge, this happens. Since DNA is a tiny molecule, it moves considerably more quickly and far than other molecules.
At the negative end of the electrophoresis, positively charged fragments will be drawn there, and the size of the molecules, not their charge, determines how they move. The larger the size of the fragments, the slower they will move.
Hence, the answer is Band 1 has longer DNA fragments than 2 and 3

Option ‘C’ is correct

Note:
The method of separating macromolecules and their fragments based on charge and size is called gel electrophoresis. It has a positive end and a negative end, and after applying an electric source, molecules are separated. Due to the agarose gel's sieving function, the molecules or fragments, such as DNA fragments, are sorted based on their size.