Given below are four statements pertaining to separation of DNA fragments using gel electrophoresis. Identify the incorrect statements. (a) DNA is negatively charged molecule and so it is loaded on gel towards the Anode terminal (b) DNA fragments travel along the surface of the gel whose concentration does not affect movement of DNA. (c) Smaller the size of DNA fragment larger is the distance it travels through it. (d) Pure DNA can be visualized directly by exposing UV radiation. Choose correct answer from the options given below

Solution & Explanation

Answer: (Option 4) (a), (b) and (d) Solution: The question asks for the INCORRECT statements. (a) is incorrect as worded only in part, but more clearly (b) is incorrect — gel (agarose) concentration provides the sieving effect and definitely affects DNA movement; (d) is incorrect — pure DNA cannot be visualized directly, it must first be stained with ethidium bromide before UV exposure. (c) is correct — smaller fragments travel farther. Statement (a)'s phrasing (DNA loaded toward the anode) is also treated as incorrect since the sample is loaded at the well/cathode end and migrates toward the anode. Thus the incorrect set is (a), (b) and (d). NCERT Reference: Ch 9, p.168, line(s) 13-19 — "separate (resolve) according to their size through sieving effect provided by the agarose gel. Hence, the smaller the fragment size, the farther it moves."