How do I do question 9? 9. The rate of DNA migration through an agarose gel is r

Question

How do I do question 9? 9. The rate of DNA migration through an agarose gel is related to the length of the DNA fragments. Shorter fragments migrate faster than longer ones. To determine fragment lengths of unknowns, we compare them to standards of known lengths run on the same gel (e.g. the ladder). For example, if an unknown fragment migrates to the same relative position as a known 0.2 kilobase (0.2kb or 200 base pairs) standard, we can then say the unknown is 0.2 kb in length. Using the gel photograph below, estimate the size in kilobases (kbo of the bands in lanes 1 through 5 by comparing them to the sizes of the DNA standard bands in the marker or ladder lane. Note: This is not the same ladder you will be using in your experiments. For this activity, you will only be able to estimate sizes 10,000 kb or less in size.

Explanation / Answer

In order to ascertain the size of an unknown DNA, we generally run a ladder along with the test samples and match the length of the test samples as compared to the ladder. From the image of the DNA gel and corresponding ladder, the lengths of the DNA samples can be directly observed as tabulated below:

10,000 bp or 10 kbp

3kbp and 2 kbp

Importantly, it should be noted here that the resolution of test DNA is made on 1.5% agarose whereas the ladder has been resolved on 0.7% agarose. While matching these DNA lengths, this assumption has been made that the resolution of both, the test DNA and ladder have been complete in the agarose.

Lane 1 2 3 4 5 Band size

10,000 bp or 10 kbp

3kbp and 2 kbp

4kbp and 1.5 kbp 4kbp and 2kbp 2.5kbp and 2kbp 3kbp

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