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Ch. 15 - Recombinant DNA Technology and Its Applications
Sanders - Genetic Analysis: An Integrated Approach 3rd Edition
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
All textbooksSanders 3rd EditionCh. 15 - Recombinant DNA Technology and Its ApplicationsProblem 4a
Chapter 15, Problem 4a

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?

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1
Understand the difference between genomic libraries and cDNA libraries: Genomic libraries contain DNA sequences from the entire genome, including both coding (exons) and non-coding regions (introns, regulatory sequences, etc.). cDNA libraries, on the other hand, are constructed from mRNA and represent only the expressed genes (coding regions) in a specific tissue at a specific time.
Consider the diversity of sequences in genomic libraries: Since genomic libraries include all DNA sequences from the genome, they inherently have greater diversity because they encompass both coding and non-coding regions, regardless of the tissue source.
Evaluate the diversity of sequences in cDNA libraries: cDNA libraries are tissue-specific and only represent the genes actively expressed in that tissue. For example, a brain cDNA library will only contain sequences from genes expressed in brain tissue, which limits its diversity compared to a genomic library.
Compare genomic libraries from different tissues: Genomic libraries made from DNA isolated from human brain tissue and human muscle tissue will have similar diversity because they represent the entire genome, not just tissue-specific expression. The source tissue does not affect the diversity of the genomic library.
Conclude which library has the greatest diversity: The genomic libraries (from either brain or muscle tissue) will have the greatest diversity of sequences because they include the entire genome, whereas cDNA libraries are limited to expressed genes in specific tissues.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Genomic Library

A genomic library is a collection of DNA fragments that represent the entire genome of an organism. It includes both coding (exons) and non-coding (introns and regulatory regions) sequences. Since it encompasses all genetic material, a genomic library typically has a high diversity of sequences, reflecting the complete genetic makeup of the source tissue.
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Genomics Overview

cDNA Library

A cDNA library is constructed from complementary DNA synthesized from mRNA transcripts. This type of library represents only the expressed genes in a specific tissue at a given time, thus it reflects the functional aspects of the genome. Consequently, a cDNA library has less diversity compared to a genomic library, as it excludes non-coding regions and genes not actively expressed in the tissue.
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Tissue-Specific Expression

Tissue-specific expression refers to the phenomenon where certain genes are expressed in specific tissues while remaining silent in others. This results in different cDNA libraries from various tissues (like brain and muscle) containing distinct sets of sequences. Therefore, while both genomic libraries have high diversity, the cDNA libraries will show less diversity due to their focus on the genes expressed in the respective tissues.
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Related Practice
Textbook Question

The human genome is 3×10⁹ bp in length.

How many fragments would be predicted to result from the complete digestion of the human genome with the following enzymes: Sau3A (˘GATC), BamHI (G˘GATCC), EcoRI (G˘AATTC), and NotI (GC˘GGCCGC)?

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Textbook Question

The human genome is 3×10⁹ bp in length.

How would your initial answer change if you knew that the average GC content of the human genome was 40%?

702
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Textbook Question

Ligase catalyzes a reaction between the 5′ phosphate and the 3′ hydroxyl groups at the ends of DNA molecules. The enzyme calf intestinal phosphatase catalyzes the removal of the 5′5′ phosphate from DNA molecules. What would be the consequence of treating a cloning vector, before ligation, with calf intestinal phosphatase?

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Textbook 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.

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?

515
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Textbook Question

Using the genomic libraries, you wish to clone the human gene encoding myostatin, which is expressed only in muscle cells.

Assuming the human genome is 3x10⁹ bp and that the average insert size in the genomic libraries is 100 kb, how frequently will a clone representing myostatin be found in the genomic library made from muscle?

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Textbook Question

Using the genomic libraries, you wish to clone the human gene encoding myostatin, which is expressed only in muscle cells.

How frequently will a clone representing myostatin be found in the genomic library made from brain?

504
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