Question

You first use PCR to amplify the fragment so that there is sufficient DNA for sequencing. You carry out dideoxy sequencing and then separate the products of the sequencing reactions by gel electrophoresis. Draw the bands that should appear on the gel from the four sequencing reactions.

Answer 1

Answer:

The first attached figure below shows the design of an agarose gel with four sequencing reactions. The second figure presents a photo of an agarose gel, so that you can better understand how the bands are represented in this gel.

Explanation:

To view the bands of four sequencing reactions on an agarose gel, you will need to use a melted agarose gel, plastic combs suitable for that reaction and a container suitable for that type of gel. You will place the plastic combs in the container and pour all the gel into the vat and wait for the melted gel to solidify. The plastic combs will form holes in the hardened gel where the DNA samples will be placed.

Once the gel is hardened, you will remove the plastic combs and begin to apply the sequenced DNA.

The sequenced DNA samples will be mixed with a dye, usually bromophenol blue, which will allow you to visualize the bands formed on the gel. You will also apply the dye to a sample without DNA containing only the dye, which serves as a comparison for the size of the bands.

Each sample of DNA will be plated in the column of holes formed by the plastic combs. Then, this container, with the gel, will be placed in a larger container that contains a loading buffer. The larger container will be closed and an electric field will be applied that will force the DNA samples to be moved from one pole to another inside the container, in this case, the samples leave the negative pole for the positive pole.

After a few minutes, it is possible to visualize the DNA displacement and at the end of the procedure it will be possible to visualize the formation of bands as shown in the drawing and in the figure below. The size of these bands can be compared and analyzed.