You isolate nuclei from three different eukaryotic specis. You treat the samples

Question

You isolate nuclei from three different eukaryotic specis. You treat the samples in exactly teh same way (adding same amount of enzyme, buffer and time) to partially digest the chromatin with micrococcal nuclease, extract the DNA, and run it on a gel. You see the pattern below:

1. Knowing that the core-DNA in all cell types is the same what is your explanation for the difference in size in the patterns you observe?

2. If you digested each of the three samples more thoroughly, what would the pattern look like? (Be specific and indicate what the size of the bands would be)

Lane Approximate size of bands (in base pairs) 1 200, 400, 600, 800 2 180, 360, 540, 720 3 190, 380, 570, 760

Explanation / Answer

Ans1.In Gel Electrophoresis, the seperation of macromolecules such as DNA or RNA takes place on the basis of size when these molecules are allowed to run on a electrically charged field or gel. Nucleic acid molecules are separated by applying an electric field to move the negatively charged molecules through a matrix of agarose or other substances. Shorter molecules move faster and migrate farther than longer ones because shorter molecules migrate more easily through the pores of the gel. This phenomenon is called sieving.

Ans2. The pattern would look like a ladder with large molecules (more base pairs) at the bottom and small moleules (less base pairs) at the top as small molecules would be able to pass through pores of small size and would run farther in a gel. The shape of bands would be thick at bootton of the "ladder" and thin at the top of the "ladder.

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