In a control experiment, a plasmid containing a HindIII recognition sequence within a kanamycin resistance gene is cut with HindIII, re-ligated, and used to transform E. coli K12 cells. Kanamycin-resistant colonies are selected, and plasmid DNA from these colonies is subjected to electrophoresis. Most of the colonies contain plasmids that produce single bands that migrate at the same rate as the original intact plasmid. A few colonies, however, produce two bands, one of original size and one that migrates much less far down the gel. Diagram the origin of this slow band as a product of ligation.

Video transcript

Hi everyone. Let's look at our next question. It says which of the following is used to analyze D. N. A. During gel electrophoresis? Well when we analyze DNA. During gel electrophoresis. Um where's two things involved in running those gels? So this can be a little bit of a confusing question because we often use both a bromo final blue and see if idiom bro mind. But our questions asking what's used to analyze the D. N. A. And that is going to be choice. E. Atheneum bromide bromide is a commonly used fluorescent tag for D. N. A. It inserts itself between base pairs between neighboring base pairs and the double helix. That's how it that's the mechanism of tagging the DNA molecule. If the gel on which you've run your DNA is illuminated with UV light you can see the location of the DNA bands, they fluoresce wherever they are. When it's been tagged when the sample's been tagged with the DDM bromide. So that's our answer here. Um The reason why choice A. Bmo final blue isn't correct. Blue blue is a stain also ph indicator and it's used as a tracking die in electrophoresis gels. So like the tedium bromine is added to the D. N. A sample that you're going to run on your gel but it's not labeling the DNA itself. It's just a blue dye that's going to run along um ahead of your D. N. A. Sample because you can't see the DNA bands without looking at your gel under UV light. So to make sure you're not going to run your D. N. A. All the way off the gel you have this blue dye tracking the progress as D. N. A. Is moving during the process of gel electrophoresis. So that's why choice. Abram final blue is not a correct answer. Then choice be the poncho S stain. This is a stain for protein, not D. N. A. And it can be used to stain and identify proteins that have been transferred onto nitrocellulose or nylon membranes during the process of western blotting. So that's why that's not our correct answer. And finally choice D. Kumasi blue stain. Um This is another protein stain and it stains proteins on sts page gels. That's why choice D. Isn't our correct answer. So we've got the two B. And D. Are stains for proteins not D. N. A. Um And then the final blue is a marker dye rather than something that actually allows you to visualize and label your D. N. A. D. N. A. Fragments themselves. So which of the following is used to analyze DNA during gel electrophoresis. Choice C. Radium bromide. See you in the next video