Anonymous
Anonymous asked in Science & MathematicsBiology · 1 decade ago

Please help with these two Biology questions.BEST ANSWER!!!!?

Based on the diagram of the gel bands when doing a agarose gel electrophoresis experiment, please answer the two questions below.Please explain your answer briefly so I understand the concept.

THANKS:)

The diagram is in the following website: http://s687.photobucket.com/albums/vv231/Suchana6/...

Questions:

1. Which sample has the smallest DNA fragment? Which sample has the largest? Do you need to run a KB ladder to know which sample has the smallest DNA fragment? Why or why not?

2. Assuming a circular piece of DNA (plasmid) was used as starting material, how many restriction sites were there in the DNA sample in lane 6? Now assume the plasmid used as starting material was linearized. How many restriction sites were there in the DNA sample in lane 6?

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  • Anonymous
    1 decade ago
    Favorite Answer

    1. Which sample has the smallest DNA fragment?

    The KB Ladder!

    Excluding that, it's S4 in Lane 6 -- the smallest fragments move the most quickly.

    > Which sample has the largest?

    The KB ladder!

    Excluding that, it's S2 in lane 4 -- the largest fragments move the slowest.

    > Do you need to run a KB ladder to know which sample has the smallest DNA fragment? Why or why not?

    Nope. You can eyeball the sample fragment bands relative to each other. The smallest fragment will be the band closest to the bottom. The KB ladder just lets you estimate how large your fragments are.

    2. Assuming a circular piece of DNA (plasmid) was used as starting material, how many restriction sites were there in the DNA sample in lane 6?

    Four sites.

    > Now assume the plasmid used as starting material was linearized. How many restriction sites were there in the DNA sample in lane 6?

    Three sites.

    3. Based on your analysis of the gel, what is your conclusion about the DNA samples in the picture?

    I haven't a clue!

    > Do any of the samples seem to be from the same source?

    If so, which ones? Describe the evidence that supports your conclusion.

    Not exactly.

    I notice that S2 and CS have two bands in common.

    S1 and S3 have one band in common.

    S3 and S4 have one band in common.

    I'm not drawing a good conclusion from this myself. You've got more recent education than I do, so... I hope you're coming up with a better answer than I did!

  • 1 decade ago

    1. S4 has the smallest (the further the bands migrate, the smaller they are) and S2 has the largest (the bigger the fragment is, the less it will migrate). No, you don't need the ladder to tell which has the smallest DNA fragment as migration is a function of size, so you can just compare the bands of the samples. You would need the ladder to approximate the size in base pairs of the DNA fragment, however.

    2. 4 restriction sites (assuming the enzyme cut every site); one cut will linearize the circular DNA, two sites will give two bands, etc. There are 4 bands, so there were 4 sites.

    If it were already linearized, then there would only need to be 3 sites to get four bands.

  • Anonymous
    5 years ago

    1) Skin (also called the integumentary system) is our largest organ and our first line of defense against pathogens (molecules). 2) Carbon dioxide is released through the alveoli (gas exchange) in the lungs. So I'd put alveoli.

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