Renaturing/re-annealing denatured DNA strands?

[dmitrip]

Renaturing/re-annealing denatured DNA strands?

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Post by dmitrip » Tue Jan 04, 2011 3:39 pm

Hello,

I am having difficulty answering the following question:

When the temperature is lowered and the original denatured DNA strands can reanneal, or renature, in addition to the full double-stranded molecules, some molecules of the type shown in the image attached are seen when the molecules are examined under the electron microscope. How can you explain these structures?

http://img267.imageshack.us/i/diagram1r.png/

any help would be greatly appreciated!
thanks

[JackBean]

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Post by JackBean » Tue Jan 04, 2011 3:47 pm

selfcomplementarity, palindroms

[dmitrip]

Re: Renaturing/re-annealing denatured DNA strands?

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Post by dmitrip » Tue Jan 04, 2011 3:50 pm

thank you JackBean for the previous answer and this answer but I think they are asking how do these "circular" structures that you can see in the picture I attached are formed? Maybe due to mistakes in complementary base pairing when the strands re-anneal?

[JackBean]

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Post by JackBean » Tue Jan 04, 2011 4:12 pm

no, they form, because one part of a strand anneals to another part of the SAME strand (normally, it should anneal to the other strand;)

[dmitrip]

Re: Renaturing/re-annealing denatured DNA strands?

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Post by dmitrip » Tue Jan 04, 2011 4:21 pm

makes sense! thank you very much:)

[canalon]

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Post by canalon » Thu Jan 06, 2011 2:32 am

By the way those circular structures, or more exactly bubbles are usually known as hairpin structures. They can be a problem when you are designing primers. They are also essential for example to the correct folding and activity of ribozymes, tRNA and of the ribosome, and they are also used to regulate the translation of some mRNA.

And your prof has master skillz with his electron microscope if he can see this kind of things. They are more commonly demonstrated with some nuclease assays.