Question

A sample mixed with bromophenol blue is run using agarose gel at a standard voltage and time. The results yield bands of 200 bp, 50 bp, and the bromophenol blue. Which of the three will migrate the shortest distance?

A) 200 bp
B) 50 bp
C) Bromophenol blue
D) All will migrate the same distance

Answer 1

The 200 bp DNA fragment will migrate the shortest distance on an agarose gel during electrophoresis because it is the largest among the samples provided, which includes a 50 bp fragment and bromophenol blue dye. Smaller molecules travel further as they experience less friction moving through the gel.

Step-by-step explanation:

The student is asking which among the bands of 200 bp, 50 bp, and bromophenol blue will migrate the shortest distance during agarose gel electrophoresis.

Electrophoretic migration in agarose gel is primarily determined by the size of the DNA fragments. Since DNA is negatively charged, it will move towards the positive electrode, and smaller fragments will move more quickly through the gel matrix because there is less friction impeding their movement. Therefore, in this context, the 200 bp DNA fragment will migrate at a slower rate compared to the 50 bp fragment and bromophenol blue dye, which acts as a tracking dye and is usually amongst the smallest molecules, allowing it to migrate quickly through the gel.

Considering the sizes provided, and assuming that all other conditions are equal, the 200 bp DNA fragment will migrate the shortest distance in an agarose gel because it is the largest molecule among the three. Bromophenol blue would typically migrate further due to its small molecular size relative to the DNA fragments.