You have constructed four different libraries: a genomic libra...

Question

You have constructed four different libraries: a genomic library made from DNA isolated from human brain tissue, a genomic library made from DNA isolated from human muscle tissue, a human brain cDNA library, and a human muscle cDNA library.

Which of these would have the greatest diversity of sequences?

Would the sequences contained in each library be expected to overlap completely, partially, or not at all with the sequences present in each of the other libraries?

Accepted Answer

Hi, everybody. Welcome back. Here's our next question. You have constructed two different libraries from the human liver tissue, the genomic library and C DNA library. What difference can you expect in the genomic and C DNA libraries of liver tissue choice? A genomic libraries contain tissue specific intron sequences and C DNA libraries contain genome wide DNA fragments. Choice B tissue origin does not affect the DNA fragments in genomic and C DNA libraries. Choice C genomic libraries have the whole genome DNA fragments and C DNA libraries have tissue specific coding sequences or choice D C DNA libraries have genome wide DNA fragments and genomic libraries have tissue specific coding sequences. Well, to think about our answer choices here, let's recall the difference between genomic and C DNA. Well, C DNA we should start with is the C stands for complementary. So that's the DNA, that's complementary to the MRN A sequences. So when you have AC DNA library, you only have DNA representing expressed genes. So gene genome sequences that have been transcribed into MRN A, so only represent transcribed regions of the genome. And of course, don't include introns because not only do you only have the parts that are transcribed. When you have your MRN A, the mature MRN A, the introns have been spiced out. So essentially C DNA libraries do not represent non coding regions of the genome. In the contrast, when you look at its very name, when we talk about a genomic library, we mean all of the DNA representing the entire genome. Now what this means in terms of the fact that we've been told it's human liver tissue, we know that different tissues have different genes expressed. That's part of what allows tissues to differentiate into different things in the body. So when we think about our two libraries, our genomic libraries will not be different in different tissues because it will represent the entire genome of the organism, which of course will be the same no matter what tissue you're in, it's the same DNA in every cell of the body. Whereas your C DNA library, since it only reflects express genes will look different. So put here different in different tissues since it only reflects expressed genes. So now that we have those things distinguished, let's evaluate our answer. Choices. Choice A has that genomic libraries contain tissue specific intron sequences. C DNA libraries contain genome wide DNA fragments. We know this is the opposite of what they contain. So choice A is not our answer. Choice. Choice. B says tissue origin does not affect the DNA fragments in genomic and C DNA libraries. Well, it doesn't affect the DNA fragments in genomic libraries. But it does and C DNA libraries since different genes will be expressed in different tissues. So put different genes, different tissues. So that's why choice B is not correct. Choice. C says genomic libraries have the whole genomes, DNA fragments. And C DNA libraries have tissue specific coding sequences and this is correct the word fragments in there is because the library, the genome is enormous. So a library has the entire genome broken into fragments of DNA sequences. And C DNA libras have those tissue specific coding sequences. Only the coding regions. Finally, choice D says that C DNA libraries have genome Y DNA fragments and genomic libraries have tissue specific coding sequences. Again, this is opposite. So choice D is incorrect. So again, what are the differences you expect in genomic and C DNA libraries of liver tissues? Choice C genomic libraries have the whole genomes DNA fragments and C DNA libraries have tissue specific coding sequences. See you in the next video.

Key Concepts

Genomic Library

cDNA Library

Gene Expression

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