Question

(i) Given below is the schematic representation of the process of electrophoresis. Identify the alphabets representing the :

(I) Anode end, and

(II) Lightest/Smallest DNA in matrix.

(ii) What is Agarose gel and why is it used in this process ?

Hint:

DNA moves from the wells towards the anode; the smallest fragments travel farthest.

Answer 1

Step 1: Read the figure:
The gel has wells (marked P) on the left. Bands of DNA lie to the right of the wells in four lanes.
The left end is marked U and the right end is marked S. Bands have moved to the right from the wells.

Step 2: Part (i)(I): the anode end:
DNA is negatively charged because of its phosphate groups. So it moves towards the positive electrode, the anode.
The bands have moved right, away from the wells, so the right end is the anode. This is S.

Step 3: Part (i)(II): the smallest DNA:
Smaller fragments move faster through the gel pores, so they travel farthest from the wells.
The band marked R lies farthest to the right. So R is the smallest or lightest DNA fragment.

Step 4: Part (ii): agarose gel:
Agarose is a natural polymer extracted from sea weeds. It forms a gel with small pores when it sets.
It is used as the matrix in electrophoresis. Its pores act like a sieve and separate DNA fragments by size. The gel also holds the fragments in place so that they can be stained and seen.

Final Answer:
(I) Anode end = S. (II) Smallest DNA = R. Agarose is a seaweed polymer that forms a sieving gel to separate DNA fragments by size.