Genomic DNA from a mouse is isolated, fragmented, and de...

Question

Genomic DNA from a mouse is isolated, fragmented, and denatured into single strands. It is then mixed with mRNA isolated from the cytoplasm of mouse cells. The image represents an electron micrograph result showing the hybridization of single-stranded DNA and mRNA.

What term best identifies the nucleic acid region indicated by the 'd' pointer?

Accepted Answer

Hello, everyone. Let's look at our next problem. It says during hybridization, when single stranded DNA and M R N A molecules with complementary base sequences come into contact, they can form a double stranded region known as a hybrid. If the DNA and M R N A molecules are physically close to each other, the hybrid can create a blank in the DNA strand due to the bending of the DNA backbone. And our answer choices are a loop B double helix C zigzag or D. All options are correct. So let's think about what's happening here. Keeping in mind that we have that option of all our answers being correct. So we have the M R N A which is complementary to the template strand of DNA. And at times that M R N A and template DNA strand form a double stranded region. This causes the formation of and we have our different shapes here. So I'm going to put up a diagram of what happens. I have a double helical DNA molecule coming along in blue. So just usual double helix, we know that the two strands get pulled apart for the transcription process. So our two strands are separated, one of the strands comes along and is now forming a double helix with a red strand of R N A. So our double helix continues along, but now it's a mix of or a hybrid of DNA and R N A, red and blue. There's still a single strand of DNA left out of this and it's coming up in a loop or a bubble away from the other strand and the R N A hybrid, then at the end of this loop, the two DNA strands rejoin each other. So that leads us straight to choice A which is loop, we have the formation of a loop here. I just gonna mark it with a, I'm just going to mark it with a dot Because we do have that choice D there and we want to make sure we don't have more than one correct answer. One important thing to note is that the formation of this loop is an important part of the regulatory process. Because of that bending, it can bring usually distant regions of DNA together. And that can be important in DNA regulation as it can bring regulatory elements uh close in proximity to our DNA strand. So just a little side note there. So let's evaluate our other answer. Choices. Choice B is double helix, but we recall the double helix is just the normal DNA structure. So that's not a structure that's created by this hybridization. So therefore, choice B is not our answer. So we can eliminate that. That also allows us to eliminate choice D all options are correct. So we can go ahead and choose choice A as our answer to be thorough, we can take a look at choice. C Choi said zigzag. This is an alternate DNA structure. It's a left handed double helix, but it's not caused by DNA R N A R N A hybridization. It's caused when there's uh a G C rich area of DNA and can cause this formation of this zigzag structure but not a result of hybridization. So not the answer we're looking for. So again, uh during hybridization, if the DNA and M R N A molecules are physically close to each other, the hybrid can create a choice a loop and the DNA strand due to the bending of the DNA backbone. See you in the next video.

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