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Carefully observe the given picture. A mixture of DNA with fragments ranging from 200 base pairs to 2500 base pairs was electrophoresed on agarose gel with the following arrangement.
![[Class 12] Carefully observe the given picture. A mixture of DNA with - Biology - CBSE Class 12 Sample Paper for 2023 Boards - Solutions](https://cdn.teachoo.com/2db4a2be-b075-4e00-9528-3d7f3fbcc4d3/question-27---carefully-observe-the-given-picture---teachoo.jpg)
(a) What result will be obtained on staining with ethidium bromide? Explain with reason.
(b) The above set-up was modified and a band with 250 base pairs was obtained at X.
What change(s) were made to the previous design to obtain a band at X? Why did the band appear at the position X?
Answer:
(a) No bands will be obtained as/All DNA will be seen in the well only;
DNA fragments being negatively charged will not move towards -ive end/ cathode. DNA being negatively charged will remain stationed at the positive end/ anodeend of the agar block;
(b)
(a) Position of the positive terminal/ end/ anode and the negative terminal/ end/ cathode was inter-changed
(ii) The fragment with least base pairs will get separated faster and move faster to the anode end.
