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Ch. 20 - The Molecular Revolution: Biotechnology, Genomics, and New Frontiers
Freeman - Biological Science 7th Edition
Freeman7th EditionBiological ScienceISBN: 9783584863285Not the one you use?Change textbook
All textbooksFreeman 7th EditionCh. 20 - The Molecular Revolution: Biotechnology, Genomics, and New FrontiersProblem 6
Chapter 20, Problem 6

Consider the validity of the following statements about genome editing. Select True or False for each statement.
T/FCas proteins work as endonucleases.
T/FsgRNA is used by bacterial cells to detect which DNA to cut.
T/FHomologous recombination is always used to join pieces of broken DNA.
T/FIt is possible to modify genes as well as disrupt them by genome editing.

Verified step by step guidance
1
Understand the role of Cas proteins: Cas proteins are part of the CRISPR system and function as endonucleases, which means they can cut DNA at specific sites. This is a key aspect of genome editing.
Explore the function of sgRNA: In the context of genome editing, sgRNA (single-guide RNA) is used to guide the Cas proteins to the specific DNA sequence that needs to be cut. However, in bacterial cells, the natural function of CRISPR is to protect against viral DNA, not to detect DNA to cut.
Examine homologous recombination: Homologous recombination is a natural process used by cells to repair broken DNA. It is not always used in genome editing, as other methods like non-homologous end joining (NHEJ) can also be employed.
Consider the possibilities of genome editing: Genome editing can be used to modify genes, such as inserting new sequences, as well as to disrupt them, which involves creating mutations or deletions.
Review each statement based on the explanations: Use the information from the previous steps to determine the validity of each statement regarding genome editing.

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Key Concepts

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

Cas Proteins as Endonucleases

Cas proteins, particularly Cas9, function as endonucleases in genome editing. They are enzymes that can cut DNA at specific sites, guided by RNA molecules. This cutting ability is crucial for the CRISPR-Cas9 system, allowing precise modifications or disruptions of target genes.
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sgRNA in Genome Editing

Single-guide RNA (sgRNA) is a synthetic RNA molecule used in genome editing to direct Cas proteins to specific DNA sequences. In the CRISPR-Cas9 system, sgRNA binds to the target DNA and guides the Cas9 enzyme to the correct location for cutting, enabling precise genetic modifications.
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Homologous Recombination in DNA Repair

Homologous recombination is a natural DNA repair mechanism that uses a homologous sequence as a template to accurately repair breaks. While it is a common method for repairing DNA, it is not always used; cells may employ other repair mechanisms like non-homologous end joining, depending on the context and available resources.
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Related Practice
Textbook Question

After finding a gene that causes a disease, researchers often introduce the defective allele into mice to create an animal model of the disease. Why are these models valuable?

a. They allow the testing of potential drug therapies without endangering human patients.

b. They allow the sequencing of the mutant allele.

c. They allow the production of large quantities of the defective gene product, usually a protein.

d. They allow the study of how the gene was transmitted from parents to offspring.

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Textbook Question

The human genome size is 3 billion base pairs, and the size of the baker's yeast genome, a single-celled organism, is 12 million base pairs. Therefore, the predicted genome size for another single-celled organism, an amoeba,

a. Is about the size of the human genome

b. Is about the size of the yeast genome

c. Is somewhere between the sizes of the yeast and human genomes

d. Cannot be predicted with any certainty

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Textbook Question

Explain how RNA-seq can be used to analyze patterns of gene expression.

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Textbook Question

Gene density is the number of genes per million base pairs (Mbp). Using Figure 20.5b, find the approximate number of genes estimated in water fleas and in humans, and note the size of each genome. Calculate the gene density in water fleas relative to that in humans.

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Textbook Question

A friend who works in a research lab performed a GWAS and discovered a tight association between a SNP allele and the disease she is studying. She concluded that the SNP allele must be the mutation that causes the disease. Explain why she is likely to be wrong.

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Textbook Question
A friend who works in a research lab performed a GWAS and discovered a tight association between a SNP allele and the disease she is studying. She concluded that the SNP allele must be the mutation that causes the disease. Explain why she is likely to be wrong.
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