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:

The anode end is S and the smallest DNA fragment is R. Agarose is a sea weed polymer that works as a sieve for DNA.

Answer 1

Step 1: Read the figure:
The wells (marked P) are at the left, near the end marked U. DNA is negatively charged, so it moves away from the wells towards the positive electrode on the right. Bands that move farther are smaller.

Step 2: Part (i)(I):
The anode (positive) end is the one towards which the DNA travels. That is the right-hand end, marked S.

Step 3: Part (i)(II):
The band at the farthest distance from the wells is the lightest or smallest DNA fragment. The farthest band, pointed to by the arrow, is R. Q is near the wells, so it is a large fragment.

Step 4: Part (ii) What agarose is:
Agarose is a natural polymer (a polysaccharide) extracted from sea weeds. It forms a gel with tiny pores when set.

Step 5: Part (ii) Why it is used:
DNA fragments pass through the pores of the agarose gel under an electric field. Small fragments move faster and farther, while large ones move slowly. So the gel acts as a sieve and separates DNA fragments by size.

Final Answer:
(i) (I) S, (II) R. (ii) Agarose is a natural polymer from sea weeds used as a sieving gel to separate DNA fragments by size.