Question

Before pouring the liquid agarose solution into the casting tray, you must first

A) Warm it to a specific temperature
B) Add the DNA sample
C) Sterilize the tray
D) Cool it to room temperature

Answer 1

Before pouring the agarose solution into a casting tray for gel electrophoresis, it is essential to cool it to room temperature. This allows the agarose to polymerize and solidify properly, forming a matrix for the DNA samples to be separated.

Step-by-step explanation:

Before pouring the liquid agarose solution into the casting tray, it must be cooled to room temperature. This is a critical step in the process of agarose gel electrophoresis, which is a method used for separating DNA fragments based on their size.

Initially, agarose powder is mixed with a buffer and then heated to ensure it is fully dissolved. Once dissolved, the mixture is allowed to cool slightly. After the cooling, but while still liquid, the solution is poured into a gel casting tray, and a comb is placed to create wells. As the agarose gel cools to room temperature, it polymerizes or solidifies. This forms the matrix through which the DNA fragments will be separated. After the gel is set, typically taking about 20 minutes, the comb is removed, creating wells where the DNA samples can later be loaded. Adding the DNA sample before the polymerization process would disrupt the formation of the gel matrix.